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Robotic Spacecraft (Astronomy, Planetary, Earth, Solar/Heliophysics) => Space Science Coverage => Topic started by: redliox on 02/07/2016 09:52 pm

Title: Pale Red Dot
Post by: redliox on 02/07/2016 09:52 pm
Between January and April there's an attempt to get spectroscopic readings of the red dwarf Proxima Centauri in an effort to find if it has any planets, Earthlike or otherwise.  Thus far they've established there's no Jovian planets around Proxima, now they seek to verify if there are any Neptunes or Earths around our neighbor.

https://palereddot.org/ (https://palereddot.org/)
Title: Re: Pale Red Dot
Post by: Borklund on 02/09/2016 01:45 pm
Very cool. Potentially habitable exoplanets are exciting, and one (or more) at our nearest star would be even more exciting. As far as I could gather from a cursory Google search, the habitable zone around Proxima Centauri is between 0.022 to about 0.054 AU, corresponding to orbital periods from 3.6 to 13.8 days. That works out to between 3.3 million to 8.1 million kilometers, a 4.8 million kilometer band. That's tiny in astronomical terms, as we know them. What would that even look like?
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 02/09/2016 03:18 pm
There had been rumours about this for a few weeks and finally as stated in their latest post, https://palereddot.org/the-signal/, the reason this campaign started was because a previous investigation found a (I should stress doubtful) possible planetary signal.  It might be an Earth-mass world and might be around the habitable zone, if it is real at all. 
Title: Re: Pale Red Dot
Post by: Bubbinski on 02/09/2016 06:52 pm
Isn't there a micro lensing event this month that can help find any planets around Proxima? As I recall there was also something similar in October 2014 and HST was taking observations. Wonder what was found.

Edit: found this, there is indeed an opportunity this month:

http://hubblesite.org/pubinfo/pdf/2013/22/pdf.pdf

If HST found something in 2014 maybe they're waiting till this month's observations to verify it?
Title: Re: Pale Red Dot
Post by: Borklund on 02/09/2016 09:52 pm
From the .pdf above:
Quote
With astrometric accuracies of 0.03 mas (achievable with HST spatial scanning), centroid shifts caused by Jovian planets are detectable at separations of up to 2′′.0 (corresponding to 2.6 AU at the distance of Proxima), and centroid shifts by Earth-mass planets are detectable within a small band of 8 mas (corresponnding to 0.01 AU) around the source trajectories. Jovian planets within a band of about 28 mas (corresponding to 0.036 AU) around the source trajectories would produce a brightening of the source by > 0.01 mag and could hence be detectable.
If I understand this correctly, microlensing would only be able to detect Jovian mass planets inside Proxima Centauri's habitable zone (?)
Title: Re: Pale Red Dot
Post by: kevin-rf on 02/10/2016 01:14 pm
Reminds me of a chinese scifi book that is currently all the rage, Liu Cixin's "The Three-Body Problem"... A story about a planet in the Centauri system.

Anyway, I'll let the electrons return the thread to the proper rest state.
Title: Re: Pale Red Dot
Post by: Bynaus on 02/10/2016 01:25 pm
From the .pdf above:
Quote
With astrometric accuracies of 0.03 mas (achievable with HST spatial scanning), centroid shifts caused by Jovian planets are detectable at separations of up to 2′′.0 (corresponding to 2.6 AU at the distance of Proxima), and centroid shifts by Earth-mass planets are detectable within a small band of 8 mas (corresponnding to 0.01 AU) around the source trajectories. Jovian planets within a band of about 28 mas (corresponding to 0.036 AU) around the source trajectories would produce a brightening of the source by > 0.01 mag and could hence be detectable.
If I understand this correctly, microlensing would only be able to detect Jovian mass planets inside Proxima Centauri's habitable zone (?)

There are two effects of microlensing: centroid shifts and brightening. Centroid shifts caused by Jovian planets can be found up until separations of 2.6 AU, while for terrestrial planets, its out to 0.01 AU. Brightening is only detectable if there is a Jovian within 0.036 AU (but we already know there likely isn't one, unless it's orbiting Proxima perpendicular to the line of sight).
Title: Re: Pale Red Dot
Post by: Borklund on 02/10/2016 10:15 pm
OK, so brightening microlensing could not detect a potentially habitable Earth or super-Earth inside Proxima's HZ in this case. If I understand the methods used by the Pale Red Dot team correctly, they have ruled out anything smaller than 3 times Earth's mass inside Proxima's H too, which is a bit of a bummer. Don't get me wrong, I'll take any and all confirmed exoplanets, but the potentially habitable ones are just that much more exciting.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 02/10/2016 11:00 pm
If I understand the methods used by the Pale Red Dot team correctly, they have ruled out anything smaller than 3 times Earth's mass inside Proxima's H too, which is a bit of a bummer.

Anything larger than ~2-3 times Earth-mass, smaller is still possible. But this is a limit on the minimum mass, msini.  Planets with a bit more true mass are still possible if the orbit is significantly inclined.
Title: Re: Pale Red Dot
Post by: notsorandom on 02/11/2016 01:27 pm
OK, so brightening microlensing could not detect a potentially habitable Earth or super-Earth inside Proxima's HZ in this case. If I understand the methods used by the Pale Red Dot team correctly, they have ruled out anything smaller than 3 times Earth's mass inside Proxima's H too, which is a bit of a bummer. Don't get me wrong, I'll take any and all confirmed exoplanets, but the potentially habitable ones are just that much more exciting.
It is amusing to me that since our techniques are better at finding bigger planets non-detection of planets increase the chance there are habitable planets. A gas giant stomping around the star systems would rule out any habitable planets so it is good that we haven't seen any. Likewise planets several times Earth's mass are questionable in terms of habitability so its good that we haven't seen any. There is still the possibility of an Earth sized planet in the habitable zone.
Title: Re: Pale Red Dot
Post by: Borklund on 02/11/2016 10:14 pm
That sounds terrific. I will follow this intently!
Title: Re: Pale Red Dot
Post by: Star One on 02/15/2016 04:51 pm
Another update.

INTERVIEW WITH SUZANNE AIGRAIN : ON THE SEARCH FOR NEARBY EARTH-LIKE EXOPLANETS

https://palereddot.org/interview-to-suzanne-aigrain-on-the-search-for-nearby-earth-like-exoplanets/
Title: Re: Pale Red Dot
Post by: redliox on 03/28/2016 09:48 pm
Pale Red Dot is entering into it's final week now.  After that it will be a matter of processing data to see if Proxima Centauri has anything small circling beside it.
Title: Re: Pale Red Dot
Post by: Ashley.Baldwin on 04/03/2016 12:36 pm
I'm lucky enough to know the Lead behind Pale Red Dot , Guillem Anglada-Escude , and was able to play a small part in the initiative through the "Centauri Dreams"  website . In return we are a chosen regular updates site , straight from the team in return for this assistance. As far as I am aware , the best Doppler signal to date has a lower mass , msini and all , of just 1.2 Mearth with an 18 day period , so well within the Hab zone.
Title: Re: Pale Red Dot
Post by: redliox on 04/03/2016 07:14 pm
As far as I am aware , the best Doppler signal to date has a lower mass , msini and all , of just 1.2 Mearth with an 18 day period , so well within the Hab zone.

How certain are they of this?  I'll be impressed if it's correct but I'd assume the odds for a planet beyond the hab zone are just as likely.  Either way, we all want to know what Proxima has circling itself.
Title: Re: Pale Red Dot
Post by: CuddlyRocket on 04/03/2016 09:46 pm
As far as I am aware , the best Doppler signal to date has a lower mass , msini and all , of just 1.2 Mearth with an 18 day period , so well within the Hab zone.

How certain are they of this?  I'll be impressed if it's correct but I'd assume the odds for a planet beyond the hab zone are just as likely.  Either way, we all want to know what Proxima has circling itself.

An Earth-sized planet within the HZ of the nearest (non-Sun) star to Earth would certainly cause a stir - science popularisers should get their soundbites ready for the inevitable media interest! How long is it likely to be before we find out?
Title: Re: Pale Red Dot
Post by: Star One on 04/18/2016 08:58 pm
Pale Red Dot –  ‏@Pale_red_dot

Campaign highlights 1 Proxima flares & rotates! Imagine the Sun bursting 10% brighter in minutes?by ASH2 #palereddot
Embedded image
2:02 a.m. - 16 Apr 2016
22 RETWEETS18 LIKES.

https://mobile.twitter.com/Pale_red_dot/status/721262539296927744
Title: Re: Pale Red Dot
Post by: Bubbinski on 08/13/2016 01:19 am
Take it for what it's worth:

http://phys.org/news/2016-08-scientists-unveil-earth-like-planet.html

If this is really real......
Title: Re: Pale Red Dot
Post by: the_other_Doug on 08/13/2016 02:03 am
Yep, but Proxima Centauri is a red dwarf, and so it's Goldilocks zone is small and close to the star.  Any Earth-sized planet in the zone will be tidally locked, which makes the sun-side a lot warmer than average, and the dark side a lot colder.  Any atmosphere would constantly rush around and the volatiles would get stuck in cold traps on the far side.  The twilight band might be livable, assuming any of the volatiles stay in a zone where it's not too warm, and not too cold, for liquid water.

As nice as it would be to find Earthlike worlds anywhere, the ones orbiting red dwarf stars are likely to have difficult conditions for life, or large amount of liquid water, due to the tidal locking issue.  It will be far more interesting to find an Earthlike world orbiting in the habitable zone of a sun-like star...
Title: Re: Pale Red Dot
Post by: meekGee on 08/13/2016 03:25 am
All true, but there are certain advantages to twilight zones that might make inhabitants thereof wonder if life can really be possible in a planet whose rotation axis does not coincide with its radius vector...

I mean, on such a planet you'd have huge differences in temperature and lighting conditions every few hours!!!  Creatures on such planets might have to develop extreme mechanisms like a suspension of body activities during the cold, dark hours..... (shudder)

And if that axis of rotation is tilted with respect to the ecliptic, my god, you'd have yearly cycles super-imposed over the daily cycles, and sometimes you'd have more darkness than light, and sometimes the other way around....

How could life ever evolve to function in such conditions?

Maybe, these creatures would suppose, maybe life could find refuge in one of the poles, where conditions must be more hospitable...
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/13/2016 03:58 am
If this is true, I predict a huge interest in interstellar travel to be renewed. Unlike anything we've yet seen.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/13/2016 07:44 am
The headquarters of ESO, who own HARPS, is in Garching Germany and so Der Spiegel have probably found a leak from there. So wouldn't surprise me if true, it's not the type of discovery that is easy to keep quiet.


Btw I don't know if this thread should be merged with the Pale Red Dot one.

http://forum.nasaspaceflight.com/index.php?topic=39533.0
Title: Re: Pale Red Dot
Post by: gospacex on 08/13/2016 09:43 am
Yep, but Proxima Centauri is a red dwarf, and so it's Goldilocks zone is small and close to the star.  Any Earth-sized planet in the zone will be tidally locked, which makes the sun-side a lot warmer than average, and the dark side a lot colder.  Any atmosphere would constantly rush around

Why would atmosphere do that? On a tidally locked planet, thermal changes over time are *less* pronounced than on Earth.

Quote
and the volatiles would get stuck in cold traps on the far side.

We have volatiles stuck in a giant cold trap on our South Pole. Not a problem as long as not all of them are stuck there.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/13/2016 10:11 am
Yep, but Proxima Centauri is a red dwarf, and so it's Goldilocks zone is small and close to the star.  Any Earth-sized planet in the zone will be tidally locked, which makes the sun-side a lot warmer than average, and the dark side a lot colder.  Any atmosphere would constantly rush around

Why would atmosphere do that? On a tidally locked planet, thermal changes over time are *less* pronounced than on Earth.
The atmospheric circularisation is nothing to do with localised thermal changes, but thermal gradients.


http://www.ast.cam.ac.uk/content/most.detailed.exoplanet.weather.map.ever
Quote
The Hubble observations show that it has winds that howl at the speed of sound from the day side that is hot enough to melt iron — soaring above 1500 degrees Celsius — to the pitch black night side that sees temperatures plunge to a comparatively cool 500 degrees Celsius.
Title: Re: Pale Red Dot
Post by: Darkseraph on 08/13/2016 10:23 am
If this is true, I predict a huge interest in interstellar travel to be renewed. Unlike anything we've yet seen.

If true it bodes well for Project Starshot! It would be easier to raise funding and institutional support knowing there are planets in the target system than a total shot in the dark.
Title: Re: Pale Red Dot
Post by: jgoldader on 08/13/2016 11:45 am
M dwarfs tend to be active, with spots and flares, and hence significant short term variability issues in both luminosity and spectra.  It will be interesting to see how the authors dealt with the activity, if this report turns out to be true.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/13/2016 12:33 pm
They monitored Proxima with other telescopes simultaneously to get photometric measurements on the magnetic activity so it can be distentangled from the doppler signal, https://palereddot.org/the-signal/
Title: Re: Pale Red Dot
Post by: Orbiter on 08/13/2016 01:24 pm
Glad to see the Pale Red Dot project may have succeeded!

Yep, but Proxima Centauri is a red dwarf, and so it's Goldilocks zone is small and close to the star.  Any Earth-sized planet in the zone will be tidally locked, which makes the sun-side a lot warmer than average, and the dark side a lot colder.  Any atmosphere would constantly rush around and the volatiles would get stuck in cold traps on the far side.  The twilight band might be livable, assuming any of the volatiles stay in a zone where it's not too warm, and not too cold, for liquid water.

True, but any planet with a sufficient atmosphere may be capable of transferring heat sufficiently to allow the planet to be at least somewhat habitable. A 1997 study, for example, suggested that a planet may need only be 0.10 atm to be sufficient enough to do this. 

http://crack.seismo.unr.edu/ftp/ftp/pub/gillett/joshi.pdf
Title: Re: Pale Red Dot
Post by: Star One on 08/13/2016 02:17 pm
M dwarfs tend to be active, with spots and flares, and hence significant short term variability issues in both luminosity and spectra.  It will be interesting to see how the authors dealt with the activity, if this report turns out to be true.

Only for the first billion years of their existence after that they calm down somewhat.
Title: Re: Pale Red Dot
Post by: Bynaus on 08/13/2016 02:26 pm
Proxima Centauri is an active flare star - right now (about 4-6 billion years into its existence). The smaller the star, the more long-lived the flare phase. And Proxima is almost as small as stars get...

But lets see what the paper actually says. Right now its all rumors and speculation. A potentially habitable world next door could indeed be a very strong incentive to try (unmanned) interstellar flight.
Title: Re: Pale Red Dot
Post by: Eric Hedman on 08/13/2016 02:53 pm
If this is true, I predict a huge interest in interstellar travel to be renewed. Unlike anything we've yet seen.
If true, hopefully it at least creates the impetus to start building telescopes that can give us a better look at planets around nearby stars.  Imagine what chemical signatures of life could do to build interest for exploration.
Title: Re: Pale Red Dot
Post by: meekGee on 08/13/2016 03:15 pm
Yep, but Proxima Centauri is a red dwarf, and so it's Goldilocks zone is small and close to the star.  Any Earth-sized planet in the zone will be tidally locked, which makes the sun-side a lot warmer than average, and the dark side a lot colder.  Any atmosphere would constantly rush around

Why would atmosphere do that? On a tidally locked planet, thermal changes over time are *less* pronounced than on Earth.

Quote
and the volatiles would get stuck in cold traps on the far side.

We have volatiles stuck in a giant cold trap on our South Pole. Not a problem as long as not all of them are stuck there.

Think of a jet engine.  The temperature and pressure are constant throughout, yet it's a very active system with lots of mass flow.

It's not a bad thing for such a planet though.   If in the habitable zone, you'll have vapor constantly flowing from the light side to the dark, and rivers flowing the other way...

Title: Re: Pale Red Dot
Post by: redliox on 08/13/2016 06:04 pm
There's a already a project called 'Red Dot' that ran a campaign.  There hopefully will be some new data to confirm whether or not Proxima has an Earth or not.
Title: Re: Pale Red Dot
Post by: Donosauro on 08/13/2016 06:38 pm
Actually, it's Pale Red Dot: https://palereddot.org
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/14/2016 01:11 am
Can't find the other tread on this topic, but here is news that ESO may have found a planet in the habitable zone of Proxima Centauri. Profound implifications if true. Supposedly will find out later in August. I've also had someone on Twitter confirm the rumor from his sources.

Article: http://www.universetoday.com/130276/earth-like-planet-around-proxima-centauri-discovered/
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/14/2016 02:02 am
From what I heard, it wasn't the Pale Red Dot team who reported the finding.
Title: Re: Pale Red Dot
Post by: Bubbinski on 08/14/2016 04:31 am
The other thread is gone for some reason (I don't know what).

But yes that would be hugely profound. I predict that if this is really a true, confirmed discovery, there will be an interstellar mission (probably robotic) launched within many of our lifetimes.

Edited to add: since the Pale Red Dot and the Hubble telescope were looking for this planet too I suspect there will be a good confirmation of this if it's really out there. There was a "gravitational lensing" alignment around Proxima Centauri that was supposed to help with finding planets in 2014 and earlier this year as I recall.
Title: Re: Pale Red Dot
Post by: Skamp_X on 08/14/2016 04:39 am
really hope this turns out to be true,
closest star , having a earth size planet, might just jump-start the spirit of cooking up a spacecraft to get there
link from other post

http://www.seeker.com/new-nearby-earth-like-planet-discovered-1970197349.html
Title: Re: Pale Red Dot
Post by: Skamp_X on 08/14/2016 04:45 am
It's the only topic that was about searching  for a planet around proxima centauri,
so I thought it was the place to bring up the link
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/14/2016 07:02 am
I would imagine the previous thread was deleted due to embargo-breaking, so this probably will be too. Seems a bit toothpaste-back-in-tube now, but that's the site-owners choice.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/14/2016 07:05 am
From what I heard, it wasn't the Pale Red Dot team who reported the finding.

Interestingly astronomer David Kipping said this, https://twitter.com/david_kipping/status/764581374099685376
Title: Re: Pale Red Dot
Post by: Ben the Space Brit on 08/14/2016 07:31 am
I'm wondering if anyone's keeping statistics here?

It seems to me that red dwarves are more likely to have planets than not. I'm wondering if it's going to turn out that the power of the primary (thus the intensity of the T-Tauri wind at fusion ignition) will have a big influence on whether the system has any native planets (as opposed to captured interstellar wanderers).
Title: Re: Pale Red Dot
Post by: Star One on 08/14/2016 09:42 am
I would imagine the previous thread was deleted due to embargo-breaking, so this probably will be too. Seems a bit toothpaste-back-in-tube now, but that's the site-owners choice.

Especially as it's now been widely reported on both specialist and general news sites. Rather reminds me of the first LIGO announcement.
Title: Re: Pale Red Dot
Post by: Chris Bergin on 08/14/2016 01:54 pm
The other thread is gone for some reason (I don't know what).


We had five threads on this and including "I think this site is an alien wacko site but I'm linking it anyway" posts (come on ;))

We can have one thread....and there's about three merged into this one.
Title: Re: Pale Red Dot
Post by: redliox on 08/14/2016 07:31 pm
The other thread is gone for some reason (I don't know what).


We had five threads on this and including "I think this site is an alien wacko site but I'm linking it anyway" posts (come on ;))

We can have one thread....and there's about three merged into this one.

The joys of forum managing, eh Chris?  ;)

Getting back to topic, the Pale Red Dot team isn't connected to the announcement, and on top of that we had the (likely) false alarm of a 'hot Earth' around Alpha Centauri B in the recent past.  The team whose announcing this Proxima discovery better have some good evidence.  Proxima has been thoroughly investigated; as an example PRD spent several months straight observing, which given a hypothetical Earth would be in a barely week-long orbit, should be ample to observe transits so long as you can meet the detection threshold and account for flare activity.  All that is pretty certain about Proxima regarding planets is that anything Neptune-size and larger has been discounted, especially in close orbits.  Given how, thanks largely to Kepler, we now know planets are indeed a common commodity for stars, it would be surprising NOT to find a planet around Proxima; we just need to verify if it can be Earthlike or not.
Title: Pale Red Dot
Post by: Star One on 08/14/2016 08:25 pm
The other thread is gone for some reason (I don't know what).


We had five threads on this and including "I think this site is an alien wacko site but I'm linking it anyway" posts (come on ;))

We can have one thread....and there's about three merged into this one.

The joys of forum managing, eh Chris?  ;)

Getting back to topic, the Pale Red Dot team isn't connected to the announcement, and on top of that we had the (likely) false alarm of a 'hot Earth' around Alpha Centauri B in the recent past.  The team whose announcing this Proxima discovery better have some good evidence.  Proxima has been thoroughly investigated; as an example PRD spent several months straight observing, which given a hypothetical Earth would be in a barely week-long orbit, should be ample to observe transits so long as you can meet the detection threshold and account for flare activity.  All that is pretty certain about Proxima regarding planets is that anything Neptune-size and larger has been discounted, especially in close orbits.  Given how, thanks largely to Kepler, we now know planets are indeed a common commodity for stars, it would be surprising NOT to find a planet around Proxima; we just need to verify if it can be Earthlike or not.

Looking online this leak appears to have already fired up interest in interstellar flight amongst the social media crowd, which is a positive.

As an aside I see Paul Gilster appears to have taken a vow of silence on this news.
Title: Pale Red Dot
Post by: Star One on 08/15/2016 06:29 am
Just as a side point doesn't it appear that the term 'earth like' is getting especially horrible misused online & with the media in this case, and leads to people imaging a planet just like Earth but with red skies. When there's likely to be no evidence of anything like that at all. Maybe a better phrase could be found to be used by those making these discoveries?
Title: Re: Pale Red Dot
Post by: redliox on 08/15/2016 06:33 am
Just as a side point doesn't it appear that the term 'earth like' is getting especially horrible misused online in this case and leads to people imaging a planet just like Earth just with red skies. When there's no likely to be no evidence of anything like that at all.

Agreed.  The bare minimum for an Earthlike planet should be a rocky planet with liquid water on the surface.  We certainly don't call Venus Earthlike as an example, nor Europa where the liquid water is under the surface.
Title: Pale Red Dot
Post by: Star One on 08/15/2016 06:37 am
Just as a side point doesn't it appear that the term 'earth like' is getting especially horrible misused online in this case and leads to people imaging a planet just like Earth just with red skies. When there's no likely to be no evidence of anything like that at all.

Agreed.  The bare minimum for an Earthlike planet should be a rocky planet with liquid water on the surface.  We certainly don't call Venus Earthlike as an example, nor Europa where the liquid water is under the surface.

I suppose the problem is how do you condense for the modern reader the ideas that it's likely to be tidally locked to an active flare star and everything that's theorised around such conditions. I mean there's competing theories about something as basic as the habitability of red dwarf planetary systems in general, let alone individual planets around a particular star.
Title: Re: Pale Red Dot
Post by: jebbo on 08/15/2016 08:32 am
Agreed.  The bare minimum for an Earthlike planet should be a rocky planet with liquid water on the surface.  We certainly don't call Venus Earthlike as an example, nor Europa where the liquid water is under the surface.

I think there are serious problems for habitability around late-M dwarfs - they are very active in their early life and the models say they'll essentially lose their atmosphere and volatiles due to this.  Add in the effect of flares and I'd be surprised if this really is habitable ... but still VERY exciting as it is a great prospect for testing a lot of the competing theories.

On the leak, I suspect it could be about the Pale Red Dot campaign as they were into first round review stuff in early July, so end of August is feasible for paper acceptance.  [ And if they had a null result, I rather suspect they wouldn't be quite so careful over embargo etc. ]

--- Tony
Title: Pale Red Dot
Post by: Star One on 08/15/2016 09:45 am
Agreed.  The bare minimum for an Earthlike planet should be a rocky planet with liquid water on the surface.  We certainly don't call Venus Earthlike as an example, nor Europa where the liquid water is under the surface.

I think there are serious problems for habitability around late-M dwarfs - they are very active in their early life and the models say they'll essentially lose their atmosphere and volatiles due to this.  Add in the effect of flares and I'd be surprised if this really is habitable ... but still VERY exciting as it is a great prospect for testing a lot of the competing theories.

On the leak, I suspect it could be about the Pale Red Dot campaign as they were into first round review stuff in early July, so end of August is feasible for paper acceptance.  [ And if they had a null result, I rather suspect they wouldn't be quite so careful over embargo etc. ]

--- Tony

Isn't one theory that a planet could possibly stay habitable around a red dwarf if it started out with an incredible thick atmosphere. But then it would probably also need an active magnetic field which I think tidal locking would preclude.
Title: Re: Pale Red Dot
Post by: jebbo on 08/15/2016 09:55 am
Isn't one theory that a planet could possibly stay habitable around a red dwarf if it started out with an incredible thick atmosphere. But then it would probably also need an active magnetic field which I think tidal locking would preclude.

Yes, but (from memory) that relies on having a larger radius (>1.5Re) so there's a large initial H/He envelope ... there are also other models which rely on later inward migration into the HZ.

But we're speculating on very poor data that could easily be wrong - the initial Der Spiegel article is hardly detailed ;-)

--- Tony
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/15/2016 09:59 am
On the leak, I suspect it could be about the Pale Red Dot campaign as they were into first round review stuff in early July, so end of August is feasible for paper acceptance.  [ And if they had a null result, I rather suspect they wouldn't be quite so careful over embargo etc. ]

--- Tony


Interestingly the palereddot team apparently said to discovermag that the leak wasn't from them. Doesn't mean it's not about them though I suppose. Also Interesting that the MOST satellite transit data is embargoed until around the same time...
Title: Re: Pale Red Dot
Post by: redliox on 08/15/2016 10:02 am
Isn't one theory that a planet could possibly stay habitable around a red dwarf if it started out with an incredible thick atmosphere. But then it would probably also need an active magnetic field which I think tidal locking would preclude.

Yes, but (from memory) that relies on having a larger radius (>1.5Re) so there's a large initial H/He envelope ... there are also other models which rely on later inward migration into the HZ.

But we're speculating on very poor data that could easily be wrong - the initial Der Spiegel article is hardly detailed ;-)

--- Tony

Presuming Proxima DOES have a rocky planet in the habitable zone, we would be able to put these quandaries and theories to the test on whether or not M-dwarfs can be viable parents to Earthlike planets. 

Interestingly the palereddot team apparently said to discovermag that the leak wasn't from them. Doesn't mean it's not about them though I suppose. Also Interesting that MOST data is embargoed until around the same time...

The claim isn't from them is certain so far.  Whether Proxima has a planet remains uncertain.
Title: Re: Pale Red Dot
Post by: jebbo on 08/15/2016 10:14 am
Presuming Proxima DOES have a rocky planet in the habitable zone, we would be able to put these quandaries and theories to the test on whether or not M-dwarfs can be viable parents to Earthlike planets. 

Indeed! Very exciting if it proves to be true ...

Quote
Interestingly the palereddot team apparently said to discovermag that the leak wasn't from them. Doesn't mean it's not about them though I suppose. Also Interesting that MOST data is embargoed until around the same time...

The claim isn't from them is certain so far.  Whether Proxima has a planet remains uncertain.

I'm suspicious it's *about* them, regardless of the source as the original Der Spiegel article claims the discovery was made at La Silla, which correlates with the Pale Red Dot HARPS campaign and I'd be amazed if there were two uncoordinated HARPS runs for the same target so close together ...

--- Tony
Title: Pale Red Dot
Post by: Star One on 08/15/2016 11:50 am
Has there been any second look study of Barnard's star for planets as that's another very close red dwarf? I can't find anything more recent than about 2012 online.
Title: Re: Pale Red Dot
Post by: Bynaus on 08/15/2016 07:29 pm
Isn't one theory that a planet could possibly stay habitable around a red dwarf if it started out with an incredible thick atmosphere. But then it would probably also need an active magnetic field which I think tidal locking would preclude.

Yes, but (from memory) that relies on having a larger radius (>1.5Re) so there's a large initial H/He envelope ... there are also other models which rely on later inward migration into the HZ.

Well, as always - it depends.

There is work that shows that, at least for some stellar masses and initial eccentricities of the planet, a magnetic field is the natural outcome for an M dwarf planet, because tidal heating cools the core which, in turn, generates a magnetic field. See here: http://arxiv.org/abs/1509.07452

Then, a thick atmosphere could inhibit tidal locking, forcing (or "allowing", whichever you prefer) the planet to rotate "unbound" as is the case for Venus. See here: http://physicsworld.com/cws/article/news/2015/jan/15/exoplanets-could-avoid-tidal-locking-if-they-have-atmospheres (link to publication in article)

Finally, the atmosphere doesn't have to be "incredibly" thick (or made of H/He) to keep up habitable conditions on a planet around a red dwarf. It depends again on the exact conditions, but already a ca. 1 bar CO2 atmosphere on an Earth-sized planet should be enough to inhibit atmospheric collapse due to freeze-out on the night side (from a 1997! paper): http://crack.seismo.unr.edu/ftp/ftp/pub/gillett/joshi.pdf

So, in summary: it depends. I am sure that, once the Proxima paper is published, we will see detailed models exploring the possibility of the planet's habitability. If we are very lucky and there is a transit, we might even be able to refine these models to the point where they become believable and constraining. That would be something...
Title: Re: Pale Red Dot
Post by: jebbo on 08/15/2016 08:19 pm
There is work that shows that, at least for some stellar masses and initial eccentricities of the planet, a magnetic field is the natural outcome for an M dwarf planet, because tidal heating cools the core which, in turn, generates a magnetic field. See here: http://arxiv.org/abs/1509.07452

Thanks, I hadn't read that one ... I was more focused on the desiccation problem (http://arxiv.org/abs/1605.00616).

Quote
So, in summary: it depends. I am sure that, once the Proxima paper is published, we will see detailed models exploring the possibility of the planet's habitability. If we are very lucky and there is a transit, we might even be able to refine these models to the point where they become believable and constraining. That would be something...

Yes, we are rather speculating in the dark ... and a transit would be fabulous (density and spectroscopy should constrain atmosphere models); without one, assuming the leak turns out to be accurate, I guess we'll have to wait for a star-shade.

--- Tony
Title: Re: Pale Red Dot
Post by: Star One on 08/15/2016 08:53 pm
There is work that shows that, at least for some stellar masses and initial eccentricities of the planet, a magnetic field is the natural outcome for an M dwarf planet, because tidal heating cools the core which, in turn, generates a magnetic field. See here: http://arxiv.org/abs/1509.07452

Thanks, I hadn't read that one ... I was more focused on the desiccation problem (http://arxiv.org/abs/1605.00616).

Quote
So, in summary: it depends. I am sure that, once the Proxima paper is published, we will see detailed models exploring the possibility of the planet's habitability. If we are very lucky and there is a transit, we might even be able to refine these models to the point where they become believable and constraining. That would be something...

Yes, we are rather speculating in the dark ... and a transit would be fabulous (density and spectroscopy should constrain atmosphere models); without one, assuming the leak turns out to be accurate, I guess we'll have to wait for a star-shade.

--- Tony
Was this a microlensing observing campaign?
Title: Re: Pale Red Dot
Post by: CuddlyRocket on 08/16/2016 02:45 am
The team whose announcing this Proxima discovery better have some good evidence.  Proxima has been thoroughly investigated; as an example PRD spent several months straight observing, which given a hypothetical Earth would be in a barely week-long orbit, should be ample to observe transits so long as you can meet the detection threshold and account for flare activity.

If the plane of the orbit is such that we're seeing it more or less edge on from our vantage point on Earth. Plenty of exoplanets discovered using the radial velocity or other methods don't transit at all.

Quote
All that is pretty certain about Proxima regarding planets is that anything Neptune-size and larger has been discounted, especially in close orbits.

Which - as I'm sure you appreciate but didn't explicitly state - doesn't rule out anything smaller than Neptune; or indeed anything larger with an orbital period longer than the period of observation.

Quote
Given how, thanks largely to Kepler, we now know planets are indeed a common commodity for stars, it would be surprising NOT to find a planet around Proxima; we just need to verify if it can be Earthlike or not.

Being pernickety (allowed in matters scientific!), it would be surprising for there not to be a planet around Proxima, but there are plenty of orbital configurations that would not be discoverable with our present techniques.

... and leads to people imaging a planet just like Earth but with red skies.

Red skies because it's orbiting a red dwarf? Another bit of public (if not your) confusion caused by astronomical terminology - which often seems as if it's designed to confuse! - not helped by all those artistic impressions etc showing red dwarfs as red etc. But if you're close enough to a red dwarf to see it as a disc, it'll appear white - as you'd expect for any object with a temperature in the thousands of degrees. If you were standing on an Earthlike planet orbiting Proxima, the skies and 'sun' would probably look pretty much the same as they do on Earth.
Title: Re: Pale Red Dot
Post by: the_other_Doug on 08/16/2016 03:29 am
Since Proxima Centauri is so close, relatively speaking, to Earth, and since Kepler-type planet detection techniques will continue to become more sensitive (and thus we will start finding planets of around one Earth mass circling red dwarves all over the place), I think it will inform our concepts of the conditions we can expect on most of these tidally-locked planets in seven- to 10-day orbits.

The more we can find out about this putative planet, the better we will understand an awful lot of the small, rocky planets out there.  And, after all, this planet would be, by definition, closer than any other extra-solar planet.  We'll have the ability to study it well before we have the ability to study other extra-solar planets, at least in the same level of detail.

So, yeah -- matters not to me if it's habitable, though that would be very cool were it so.  But just by existing, and being so close, it would provide extremely valuable data.
Title: Re: Pale Red Dot
Post by: Star One on 08/16/2016 06:22 am
The team whose announcing this Proxima discovery better have some good evidence.  Proxima has been thoroughly investigated; as an example PRD spent several months straight observing, which given a hypothetical Earth would be in a barely week-long orbit, should be ample to observe transits so long as you can meet the detection threshold and account for flare activity.

If the plane of the orbit is such that we're seeing it more or less edge on from our vantage point on Earth. Plenty of exoplanets discovered using the radial velocity or other methods don't transit at all.

Quote
All that is pretty certain about Proxima regarding planets is that anything Neptune-size and larger has been discounted, especially in close orbits.

Which - as I'm sure you appreciate but didn't explicitly state - doesn't rule out anything smaller than Neptune; or indeed anything larger with an orbital period longer than the period of observation.

Quote
Given how, thanks largely to Kepler, we now know planets are indeed a common commodity for stars, it would be surprising NOT to find a planet around Proxima; we just need to verify if it can be Earthlike or not.

Being pernickety (allowed in matters scientific!), it would be surprising for there not to be a planet around Proxima, but there are plenty of orbital configurations that would not be discoverable with our present techniques.

... and leads to people imaging a planet just like Earth but with red skies.

Red skies because it's orbiting a red dwarf? Another bit of public (if not your) confusion caused by astronomical terminology - which often seems as if it's designed to confuse! - not helped by all those artistic impressions etc showing red dwarfs as red etc. But if you're close enough to a red dwarf to see it as a disc, it'll appear white - as you'd expect for any object with a temperature in the thousands of degrees. If you were standing on an Earthlike planet orbiting Proxima, the skies and 'sun' would probably look pretty much the same as they do on Earth.

Not my belief merely a turn of phrase to illustrate the kind of imaginings I've already seen online to illustrate this proposed planet.

As asked up thread was wondering if this discovery is announced that Barnard's star will now get a second look for planets?
Title: Re: Pale Red Dot
Post by: Bynaus on 08/16/2016 06:33 am
The Pale Red Dot team has certainly expressed their interest to look at other near-by red dwarfs after Proxima (https://palereddot.org/m-dwarf-planet-search-with-todays-spectrographs-and-tomorrows-spectropolarimeters/)... After all, with all the infrastructure in place, why not?

From the surface of a Proxima planet recieving the same amount of insolation as the Earth (1367 W/m2), the star would look white but slightly dimmer than Sol (perhaps unnoticably so), because a higher relative fraction of that insolation is outside the visible range (i.e., peak flux moved towards the infrared).
Title: Re: Pale Red Dot
Post by: Star One on 08/16/2016 07:47 am
The Pale Red Dot team has certainly expressed their interest to look at other near-by red dwarfs after Proxima (https://palereddot.org/m-dwarf-planet-search-with-todays-spectrographs-and-tomorrows-spectropolarimeters/)... After all, with all the infrastructure in place, why not?

From the surface of a Proxima planet recieving the same amount of insolation as the Earth (1367 W/m2), the star would look white but slightly dimmer than Sol (perhaps unnoticably so), because a higher relative fraction of that insolation is outside the visible range (i.e., peak flux moved towards the infrared).

How big approximately would Proxima appear in the sky for a planet in the habitable zone? I've seen illustrations portraying it as literally filling the whole horizon virtually.
Title: Re: Pale Red Dot
Post by: Bynaus on 08/16/2016 09:15 am
14% of solar radius / ~0.03 AU distance = ~5 times the diameter of the Sun on Earth.
Title: Re: Pale Red Dot
Post by: Star One on 08/16/2016 09:43 am
14% of solar radius / ~0.03 AU distance = ~5 times the diameter of the Sun on Earth.

Thank you. Not quite how it's portrayed in some illustrations I've seen then.
Title: Re: Pale Red Dot
Post by: jgoldader on 08/16/2016 12:58 pm
It would be very, very difficult to study a little rock so close to its star.  If it transits, you could try to study the atmosphere by looking for absorption during the transit.  But an M star has so many lines of its own, that will be tough.  Direct imaging is probably out using any current technique, the planet would be so deep within the point spread function of the star.
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/16/2016 01:18 pm
It would be very, very difficult to study a little rock so close to its star.  If it transits, you could try to study the atmosphere by looking for absorption during the transit.  But an M star has so many lines of its own, that will be tough.  Direct imaging is probably out using any current technique, the planet would be so deep within the point spread function of the star.
It is not out of reach of mid-term imaging techniques, though, and there would be a strong motivation to build the equipment needed to image it. If it is indeed in the habitable zone, then I can definitely imagine a project more ambitious than even James Webb to image it. It would push our technology forward.

What an exciting time to be alive! It's like a new Galilean revolution, but with the actual possibility of sending out an emissary within a few generations.
Title: Re: Pale Red Dot
Post by: Star One on 08/16/2016 01:27 pm
It would be very, very difficult to study a little rock so close to its star.  If it transits, you could try to study the atmosphere by looking for absorption during the transit.  But an M star has so many lines of its own, that will be tough.  Direct imaging is probably out using any current technique, the planet would be so deep within the point spread function of the star.
It is not out of reach of mid-term imaging techniques, though, and there would be a strong motivation to build the equipment needed to image it. If it is indeed in the habitable zone, then I can definitely imagine a project more ambitious than even James Webb to image it. It would push our technology forward.

What an exciting time to be alive! It's like a new Galilean revolution, but with the actual possibility of sending out an emissary within a few generations.

If the JWST ever gets that proposed large free flying Coronagraph wouldn't it be able to image it then?
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/16/2016 02:30 pm
No, still far too large an inner working angle.
Title: Re: Pale Red Dot
Post by: jebbo on 08/16/2016 06:04 pm
No, still far too large an inner working angle.

Hmm .. this study from 2012 suggests there may be hope for proxima Centauri, though I'd like to see an update given the progress in habitability since then.

http://arxiv.org/abs/1204.6063

--- Tony
Title: Re: Pale Red Dot
Post by: Star One on 08/16/2016 06:38 pm
No, still far too large an inner working angle.

Hmm .. this study from 2012 suggests there may be hope for proxima Centauri, though I'd like to see an update given the progress in habitability since then.

http://arxiv.org/abs/1204.6063

--- Tony

Will James Webb be powerful enough to see starspot activity on Proxima Centauri which in of itself would be a major achievement.
Title: Re: Pale Red Dot
Post by: as58 on 08/16/2016 07:24 pm
Will James Webb be powerful enough to see starspot activity on Proxima Centauri which in of itself would be a major achievement.

What do you mean by "see"? It can't resolve the stellar disk, the angular diameter of the star is much too small for that.

I guess it could detect the brightness variations caused by starspots, but I don't see why a number of other existing telescopes couldn't do that as well (and I'd guess it's already been done). Anyway, I don't see why it would be a particularly major achievement.
Title: Re: Pale Red Dot
Post by: Phil Stooke on 08/16/2016 07:29 pm
Starspot maps are available for many stars already, via various imaging techniques .  Example:

http://articles.adsabs.harvard.edu//full/2004IAUS..219..873G/0000876.000.html (http://articles.adsabs.harvard.edu//full/2004IAUS..219..873G/0000876.000.html)

Title: Re: Pale Red Dot
Post by: Star One on 08/16/2016 07:46 pm
Starspot maps are available for many stars already, via various imaging techniques .  Example:

http://articles.adsabs.harvard.edu//full/2004IAUS..219..873G/0000876.000.html (http://articles.adsabs.harvard.edu//full/2004IAUS..219..873G/0000876.000.html)
Oh after that announcement last year about XX Trianguli I thought it was a major breakthrough.
Title: Re: Pale Red Dot
Post by: CuddlyRocket on 08/16/2016 07:56 pm
... and leads to people imaging a planet just like Earth but with red skies.

Red skies because it's orbiting a red dwarf? Another bit of public (if not your) confusion caused by astronomical terminology - which often seems as if it's designed to confuse! - not helped by all those artistic impressions etc showing red dwarfs as red etc. But if you're close enough to a red dwarf to see it as a disc, it'll appear white - as you'd expect for any object with a temperature in the thousands of degrees. If you were standing on an Earthlike planet orbiting Proxima, the skies and 'sun' would probably look pretty much the same as they do on Earth.

Not my belief merely a turn of phrase to illustrate the kind of imaginings I've already seen online to illustrate this proposed planet.

No, I didn't think you'd make that mistake. I hope that none of these 'imaginings' come from sources who should know better!

From the surface of a Proxima planet recieving the same amount of insolation as the Earth (1367 W/m2), the star would look white but slightly dimmer than Sol (perhaps unnoticably so), because a higher relative fraction of that insolation is outside the visible range (i.e., peak flux moved towards the infrared).
14% of solar radius / ~0.03 AU distance = ~5 times the diameter of the Sun on Earth.

With 5x the diameter, that's 25x the area on the sky. So with the same amount of insolation that's 1/25 or 4% per unit area; even less after accounting for the greater amount outside the visible range. So, about 3 magnitudes dimmer than the Sun, which would be noticeable? Though the daytime sky should be about the same brightness as on Earth!
Title: Re: Pale Red Dot
Post by: as58 on 08/16/2016 08:12 pm
Starspot maps are available for many stars already, via various imaging techniques .  Example:

http://articles.adsabs.harvard.edu//full/2004IAUS..219..873G/0000876.000.html (http://articles.adsabs.harvard.edu//full/2004IAUS..219..873G/0000876.000.html)
Oh after that announcement last year about XX Trianguli I thought it was a major breakthrough.

Proxima Centauri is a very slow rotator, so the same method (Doppler imaging) that was used for XX Trianguli isn't possible. This isn't my specialty, but I don't think it's currently possible to obtain such maps of starspots on a star like Proxima Centauri. Some more general information about size and distribution of spots should be available from photometric variation.

And indeed, a quick search finds this paper:
http://adsabs.harvard.edu/abs/1998AJ....116..429B
Title: Re: Pale Red Dot
Post by: jebbo on 08/17/2016 08:36 am
One of the team is tweeting teasers ... so I think the release of the PaleRedDot paper is imminent! My guess is tomorrow.

--- Tony
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/17/2016 09:42 am
I would have thought they would wait til the Olympics has finished for maximum publicity.
Title: Re: Pale Red Dot
Post by: Bynaus on 08/17/2016 10:19 am
One of the team is tweeting teasers ... so I think the release of the PaleRedDot paper is imminent! My guess is tomorrow.

--- Tony

Can you link to the tweet, please?
Title: Re: Pale Red Dot
Post by: jebbo on 08/17/2016 03:25 pm
One of the team is tweeting teasers ... so I think the release of the PaleRedDot paper is imminent! My guess is tomorrow.

--- Tony

Can you link to the tweet, please?

Sure ... Mikko retweeted this one from July: https://twitter.com/mustapipa/status/754669650286379008
Part of a set of retweets  (see attached for part of it; screenshot doesn't get it all)

--- Tony
Title: Re: Pale Red Dot
Post by: gospacex on 08/17/2016 04:08 pm
Yep, but Proxima Centauri is a red dwarf, and so it's Goldilocks zone is small and close to the star.  Any Earth-sized planet in the zone will be tidally locked, which makes the sun-side a lot warmer than average, and the dark side a lot colder.  Any atmosphere would constantly rush around

Why would atmosphere do that? On a tidally locked planet, thermal changes over time are *less* pronounced than on Earth.
The atmospheric circularisation is nothing to do with localised thermal changes, but thermal gradients.


http://www.ast.cam.ac.uk/content/most.detailed.exoplanet.weather.map.ever
Quote
The Hubble observations show that it has winds that howl at the speed of sound from the day side that is hot enough to melt iron — soaring above 1500 degrees Celsius — to the pitch black night side that sees temperatures plunge to a comparatively cool 500 degrees Celsius.

The article is about a planet with ultra-short, *19 hour orbit*.

Planet in a habitable zone will not have temps of 1500 C in a sub-solar point.

I agree that some winds will be induced by temperature gradient, but at the same time cyclic day/night winds disappear because there is no day/night cycle. Therefore tidally locked planets are different, but not necessarily more windy.
Title: Re: Pale Red Dot
Post by: jebbo on 08/17/2016 04:14 pm

The article is about a planet with ultra-short, *19 hour orbit*.

Planet in a habitable zone will not have temps of 1500 C in a sub-solar point.

I agree that some winds will be induced by temperature gradient, but at the same time cyclic day/night winds disappear because there is no day/night cycle. Therefore tidally locked planets are different, but not necessarily more windy.

There is some good treatment of synchronous rotators and the sub-solar point here: http://arxiv.org/abs/1602.05176

--- Tony
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/18/2016 08:46 am
https://mobile.twitter.com/chrislintott/status/766171247256412160
Quote
Off to film a secret #skyatnight today. Exciting news coming. (PS it's not aliens)

Pretty much confirmation it is true.
Title: Pale Red Dot
Post by: Star One on 08/18/2016 05:03 pm
Could Proxima Centauri Be Our Interstellar Getaway?

Quote
"The discovery of a habitable planet orbiting Proxima Centauri could have a profound impact on humanity's interstellar future," said advanced propulsion expert Richard Obousy, co-founder and director of the non-profit group Icarus Interstellar. "It would be easy to dismiss the prospects of an interstellar mission if a habitable planet were found perhaps fifty, or even hundreds of light-years away. However, an 'Earth 2.0' on our galactic doorstep almost teases us into us taking action."

Quote
"Ideally, a mission would take fifty years or less," said Obousy. "This would mean that people working on the mission early on in their career would have a realistic chance at seeing the mission completed in their lifetime."

For this to happen we need new technologies that would allow an interstellar probe to travel at least 10% the speed of light. Remember, for us to merely send an electromagnetic signal (traveling at the speed of light) to Proxima Centauri, it would take that signal 4.25 years to get there. (As a comparison, it currently takes nearly 19 hours for us to receive radio communications from Voyager 1. If Proxima is on our galactic doorstep, Voyager 1 has barely cracked opened the galactic door!)

Quote
"The truth of the matter is that Earth 2.0 orbiting Proxima Centauri means that this is as easy as it could get for us, in terms of difficulty," said Obousy. "That's not to say that it's an easy challenge, far from it, but we could not wish for better terms as we begin to reach out into our cosmic neighborhood."

http://www.seeker.com/could-proxima-centauri-be-our-interstellar-getaway-1977439925.html

Actually a fairly measures article.
Title: Pale Red Dot
Post by: Star One on 08/18/2016 08:07 pm
More hints...

https://mobile.twitter.com/BadAstronomer/status/766290250331283456

Quote
chrislintott – Verified account ‏@chrislintott

Secret #skyatnight mission complete. Exciting!
12:16 pm - 18 Aug 2016

https://mobile.twitter.com/chrislintott/status/766353171161681920




Title: Re: Pale Red Dot
Post by: philw1776 on 08/18/2016 09:56 pm
Isn't one theory that a planet could possibly stay habitable around a red dwarf if it started out with an incredible thick atmosphere. But then it would probably also need an active magnetic field which I think tidal locking would preclude.

Yes, but (from memory) that relies on having a larger radius (>1.5Re) so there's a large initial H/He envelope ... there are also other models which rely on later inward migration into the HZ.

Well, as always - it depends.

There is work that shows that, at least for some stellar masses and initial eccentricities of the planet, a magnetic field is the natural outcome for an M dwarf planet, because tidal heating cools the core which, in turn, generates a magnetic field. See here: http://arxiv.org/abs/1509.07452

Then, a thick atmosphere could inhibit tidal locking, forcing (or "allowing", whichever you prefer) the planet to rotate "unbound" as is the case for Venus. See here: http://physicsworld.com/cws/article/news/2015/jan/15/exoplanets-could-avoid-tidal-locking-if-they-have-atmospheres (link to publication in article)

Finally, the atmosphere doesn't have to be "incredibly" thick (or made of H/He) to keep up habitable conditions on a planet around a red dwarf. It depends again on the exact conditions, but already a ca. 1 bar CO2 atmosphere on an Earth-sized planet should be enough to inhibit atmospheric collapse due to freeze-out on the night side (from a 1997! paper): http://crack.seismo.unr.edu/ftp/ftp/pub/gillett/joshi.pdf

So, in summary: it depends. I am sure that, once the Proxima paper is published, we will see detailed models exploring the possibility of the planet's habitability. If we are very lucky and there is a transit, we might even be able to refine these models to the point where they become believable and constraining. That would be something...

Plus we have seen that many M stars have several planets, some quite massive condensed into a relatively (to our) close planetary system.  If this is so with Proxima, it's quite possible that resonance effects could prevent tidal lock and the HZ planet could rotate in some resonance with an outer, yet nearby planetary companion.
Title: Re: Pale Red Dot
Post by: KelvinZero on 08/19/2016 02:52 am
Could Proxima Centauri Be Our Interstellar Getaway?

Quote
"The truth of the matter is that Earth 2.0 orbiting Proxima Centauri means that this is as easy as it could get for us, in terms of difficulty," said Obousy. "That's not to say that it's an easy challenge, far from it, but we could not wish for better terms as we begin to reach out into our cosmic neighborhood."

http://www.seeker.com/could-proxima-centauri-be-our-interstellar-getaway-1977439925.html

Actually a fairly measures article.
I like to use the example that if the moon had been another earthlike planet (just not quite close enough that we could drop people on it one way and they could start farming) we surely couldn't have even visited it by now.

Think about the huge effort to get to earth orbit compared to the lunar ascent vehicle. Now imagine dropping all that infrastructure from the sky and being able to return all the ground crew to run that infrastructure, not just the handful you can fit in a capsule.

I think the solarsystem we have is just awesome. The lunar poles, Mars, and NEA resources are all plausibly in reach right now, give or take a decade or two, all arguably better than an earth 2.0.

However this is still cool and I don't think any interest it inspires will go to waste so I will stop being a wet blanket.
Title: Re: Pale Red Dot
Post by: Star One on 08/19/2016 05:56 am
Isn't one theory that a planet could possibly stay habitable around a red dwarf if it started out with an incredible thick atmosphere. But then it would probably also need an active magnetic field which I think tidal locking would preclude.

Yes, but (from memory) that relies on having a larger radius (>1.5Re) so there's a large initial H/He envelope ... there are also other models which rely on later inward migration into the HZ.

Well, as always - it depends.

There is work that shows that, at least for some stellar masses and initial eccentricities of the planet, a magnetic field is the natural outcome for an M dwarf planet, because tidal heating cools the core which, in turn, generates a magnetic field. See here: http://arxiv.org/abs/1509.07452

Then, a thick atmosphere could inhibit tidal locking, forcing (or "allowing", whichever you prefer) the planet to rotate "unbound" as is the case for Venus. See here: http://physicsworld.com/cws/article/news/2015/jan/15/exoplanets-could-avoid-tidal-locking-if-they-have-atmospheres (link to publication in article)

Finally, the atmosphere doesn't have to be "incredibly" thick (or made of H/He) to keep up habitable conditions on a planet around a red dwarf. It depends again on the exact conditions, but already a ca. 1 bar CO2 atmosphere on an Earth-sized planet should be enough to inhibit atmospheric collapse due to freeze-out on the night side (from a 1997! paper): http://crack.seismo.unr.edu/ftp/ftp/pub/gillett/joshi.pdf

So, in summary: it depends. I am sure that, once the Proxima paper is published, we will see detailed models exploring the possibility of the planet's habitability. If we are very lucky and there is a transit, we might even be able to refine these models to the point where they become believable and constraining. That would be something...

Plus we have seen that many M stars have several planets, some quite massive condensed into a relatively (to our) close planetary system.  If this is so with Proxima, it's quite possible that resonance effects could prevent tidal lock and the HZ planet could rotate in some resonance with an outer, yet nearby planetary companion.

I was going to ask this, that could they have discovered not just a singular planet but a whole compressed solar system.
Title: Re: Pale Red Dot
Post by: Bynaus on 08/19/2016 11:23 am
Isn't one theory that a planet could possibly stay habitable around a red dwarf if it started out with an incredible thick atmosphere. But then it would probably also need an active magnetic field which I think tidal locking would preclude.

Yes, but (from memory) that relies on having a larger radius (>1.5Re) so there's a large initial H/He envelope ... there are also other models which rely on later inward migration into the HZ.

Well, as always - it depends.

There is work that shows that, at least for some stellar masses and initial eccentricities of the planet, a magnetic field is the natural outcome for an M dwarf planet, because tidal heating cools the core which, in turn, generates a magnetic field. See here: http://arxiv.org/abs/1509.07452

Then, a thick atmosphere could inhibit tidal locking, forcing (or "allowing", whichever you prefer) the planet to rotate "unbound" as is the case for Venus. See here: http://physicsworld.com/cws/article/news/2015/jan/15/exoplanets-could-avoid-tidal-locking-if-they-have-atmospheres (link to publication in article)

Finally, the atmosphere doesn't have to be "incredibly" thick (or made of H/He) to keep up habitable conditions on a planet around a red dwarf. It depends again on the exact conditions, but already a ca. 1 bar CO2 atmosphere on an Earth-sized planet should be enough to inhibit atmospheric collapse due to freeze-out on the night side (from a 1997! paper): http://crack.seismo.unr.edu/ftp/ftp/pub/gillett/joshi.pdf

So, in summary: it depends. I am sure that, once the Proxima paper is published, we will see detailed models exploring the possibility of the planet's habitability. If we are very lucky and there is a transit, we might even be able to refine these models to the point where they become believable and constraining. That would be something...

Plus we have seen that many M stars have several planets, some quite massive condensed into a relatively (to our) close planetary system.  If this is so with Proxima, it's quite possible that resonance effects could prevent tidal lock and the HZ planet could rotate in some resonance with an outer, yet nearby planetary companion.

I was going to ask this, that could they have discovered not just a singular planet but a whole compressed solar system.

Might be. There are many compact multiple systems out there - would be kind of strange if Proxima turned out to be an outlier.

But I am not so sure that having additional planets would keep them from being tidally locked - see, e.g., the very compact satellite system around Jupiter (which is actually a good example for a compact M dwarf system, in terms of mass ratios and relative distances) - everything still tidally locked. The only way I could see this working is if having additional planets would induce eccentricity in the orbit of the planet of interest, which in turn would break the tidal lock (as in the case of Mercury, where the 2:3 lock is actually more stable given its eccentric orbit than a 1:1 lock). However, this would also mean additional tidal heating (as the star would try to circularize the orbit again), so you might end up with a planet looking like Io...
Title: Re: Pale Red Dot
Post by: Star One on 08/19/2016 06:36 pm
Saw a comment online that if these rumours are true then long-baseline optical interferometry is going to get very popular very fast.
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/19/2016 07:43 pm
Could Proxima Centauri Be Our Interstellar Getaway?

Quote
"The truth of the matter is that Earth 2.0 orbiting Proxima Centauri means that this is as easy as it could get for us, in terms of difficulty," said Obousy. "That's not to say that it's an easy challenge, far from it, but we could not wish for better terms as we begin to reach out into our cosmic neighborhood."

http://www.seeker.com/could-proxima-centauri-be-our-interstellar-getaway-1977439925.html

Actually a fairly measures article.
I like to use the example that if the moon had been another earthlike planet (just not quite close enough that we could drop people on it one way and they could start farming) we surely couldn't have even visited it by now.

Think about the huge effort to get to earth orbit compared to the lunar ascent vehicle. Now imagine dropping all that infrastructure from the sky and being able to return all the ground crew to run that infrastructure, not just the handful you can fit in a capsule.
But easy. Just send them one-way. They can set up communications. No return journey is necessary if it's habitable. Just keep sending people. And really, with a nice atmosphere, you could do entry with just a heatshield and a 'chute, which makes the lander much cheaper. Sending pallets of equipment would be relatively easy, then. Land 100 tons of storable propellant that way, and they could fuel up a dry launch vehicle big enough to send some people back into orbit.

It'd be way easier, and since we'd have more motivation, we'd probably have developed an RLV, perhaps even a single-stage one. That'd make two-way travel really simple, once you had a reactor installed that could be used for producing hydrogen and oxygen.

Quote
I think the solarsystem we have is just awesome. The lunar poles, Mars, and NEA resources are all plausibly in reach right now, give or take a decade or two, all arguably better than an earth 2.0.

However this is still cool and I don't think any interest it inspires will go to waste so I will stop being a wet blanket.
It just takes a lot of imagination, a lot of physics, a lot of engineering, and a lot of cash. But we can do interstellar travel.
Title: Re: Pale Red Dot
Post by: Star One on 08/19/2016 08:58 pm
Could Proxima Centauri Be Our Interstellar Getaway?

Quote
"The truth of the matter is that Earth 2.0 orbiting Proxima Centauri means that this is as easy as it could get for us, in terms of difficulty," said Obousy. "That's not to say that it's an easy challenge, far from it, but we could not wish for better terms as we begin to reach out into our cosmic neighborhood."

http://www.seeker.com/could-proxima-centauri-be-our-interstellar-getaway-1977439925.html

Actually a fairly measures article.
I like to use the example that if the moon had been another earthlike planet (just not quite close enough that we could drop people on it one way and they could start farming) we surely couldn't have even visited it by now.

Think about the huge effort to get to earth orbit compared to the lunar ascent vehicle. Now imagine dropping all that infrastructure from the sky and being able to return all the ground crew to run that infrastructure, not just the handful you can fit in a capsule.

I think the solarsystem we have is just awesome. The lunar poles, Mars, and NEA resources are all plausibly in reach right now, give or take a decade or two, all arguably better than an earth 2.0.

However this is still cool and I don't think any interest it inspires will go to waste so I will stop being a wet blanket.

Being as we only have one Earth in the Solar System, if one day we find a similar planet I can't see that as being anything other than remarkable and if it's next door so to speak ten times so.
Title: Re: Pale Red Dot
Post by: KelvinZero on 08/19/2016 11:41 pm
But easy. Just send them one-way. They can set up communications. No return journey is necessary if it's habitable.
Yeah I was postulating not quite habitable. I figure it either has no/little oxygen or it has competing life so it would really be an unknown how much effort would be required before a colony became self sufficient. I think a landing would politically be a very difficult decision to have made.

Of course the analogy fails quickly with examination because if there were an earth 2.0 instead of the moon, it might well be seeded with earth life, and it would be close enough that we could keep landing robotic agriculture experiments until we were confident that a one way trip was ok.

My point was just that people discuss an earth 2.0 as an enabler to becoming a colonising species and I think this thinking holds us back. By the time we get that far I expect we will have a hundred worlds under our belt. Even the ability to send a self sufficient seed colony on a decades-long trip probably proves you don't need an earth 2.0. This is the opposite of stay at home pessimism.
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/20/2016 04:30 am
But easy. Just send them one-way. They can set up communications. No return journey is necessary if it's habitable.
Yeah I was postulating not quite habitable. I figure it either has no/little oxygen or it has competing life so it would really be an unknown how much effort would be required before a colony became self sufficient. I think a landing would politically be a very difficult decision to have made.

Of course the analogy fails quickly with examination because if there were an earth 2.0 instead of the moon, it might well be seeded with earth life, and it would be close enough that we could keep landing robotic agriculture experiments until we were confident that a one way trip was ok.

My point was just that people discuss an earth 2.0 as an enabler to becoming a colonising species and I think this thinking holds us back. By the time we get that far I expect we will have a hundred worlds under our belt. Even the ability to send a self sufficient seed colony on a decades-long trip probably proves you don't need an earth 2.0. This is the opposite of stay at home pessimism.
Sure, but I think a garden world will still be a garden world.

I of all people don't think we need an exoplanet to become a multiplanetary species ("Occupy Mars"), but I definitely think a second Earth would be tremendously motivating for interstellar travel.
Title: Re: Pale Red Dot
Post by: CuddlyRocket on 08/20/2016 10:05 pm
But I am not so sure that having additional planets would keep them from being tidally locked - see, e.g., the very compact satellite system around Jupiter (which is actually a good example for a compact M dwarf system, in terms of mass ratios and relative distances) - everything still tidally locked. The only way I could see this working is if having additional planets would induce eccentricity in the orbit of the planet of interest, which in turn would break the tidal lock (as in the case of Mercury, where the 2:3 lock is actually more stable given its eccentric orbit than a 1:1 lock). However, this would also mean additional tidal heating (as the star would try to circularize the orbit again), so you might end up with a planet looking like Io...

Another possibility is to have a proportionally large moon. I calculate the Hill radius for an Earth-mass planet at 0.03 AU from Proxima to be about 130,000 km, so a moon is possible. If such a moon is big enough and close enough, the planet would become tidally locked to the moon rather than Proxima.

Granted, there's a lot of 'ifs' there!
Title: Re: Pale Red Dot
Post by: Star One on 08/20/2016 10:10 pm
But easy. Just send them one-way. They can set up communications. No return journey is necessary if it's habitable.
Yeah I was postulating not quite habitable. I figure it either has no/little oxygen or it has competing life so it would really be an unknown how much effort would be required before a colony became self sufficient. I think a landing would politically be a very difficult decision to have made.

Of course the analogy fails quickly with examination because if there were an earth 2.0 instead of the moon, it might well be seeded with earth life, and it would be close enough that we could keep landing robotic agriculture experiments until we were confident that a one way trip was ok.

My point was just that people discuss an earth 2.0 as an enabler to becoming a colonising species and I think this thinking holds us back. By the time we get that far I expect we will have a hundred worlds under our belt. Even the ability to send a self sufficient seed colony on a decades-long trip probably proves you don't need an earth 2.0. This is the opposite of stay at home pessimism.
Sure, but I think a garden world will still be a garden world.

I of all people don't think we need an exoplanet to become a multiplanetary species ("Occupy Mars"), but I definitely think a second Earth would be tremendously motivating for interstellar travel.
Mars is a dead end. If we want to last longer term interstellar is the only way to go.
Title: Re: Pale Red Dot
Post by: cro-magnon gramps on 08/21/2016 12:21 am
I agree with Robotbeat and Star One:

Robotbeat, because we are playing in our own garden. Exploring and testing our capabilities. Stretching and exercising our muscles as we grow into our destiny. Cis-Lunar and LEO have been good for us for 50 years. The Space Age began 10,000+ years ago with henges and astronomical stones. It has steadily picked up speed. We have nothing to be ashamed of that time. In fact the last 3-400 years have accelerated out of all proportions to the previous 9,600 years. To actually have a chance in this generation to land on Mars, with a slim possibility of staying there, for this species is akin to coming down from the trees and walking upright. A Stupendous achievement. We have the technology and the will to take that leap and propel us into the wider solar system, with advancements beyond today's reason.

But we can't just stop there, as Star One says, to stay here is a dead end. Just as staying in Africa was a dead end. We need to travel the interstellar space lanes. The study of exo-planets has opened a huge field of knowledge, the likes of which was not known 10-20 years ago. A lot of that "general knowledge" is on parade here in this thread. Stuff that is going to become as common knowledge to future generations, as the reading of maps, sextons and tide tables became to the generations during the age of discovery from 1300 to 1800 ad. A scant 700 to 200 years ago.

I won't dare to predict how soon we will be, as living beings, traveling beyond this solar systems outer edges. Except to say, hold onto your seats, you ain't seen nuthin' yet!! The human species is breaking out of it's  Chrysalis and the Universe better be ready...

Title: Re: Pale Red Dot
Post by: redliox on 08/21/2016 01:16 am
As much as I like the thought of humans going all 'Star Trek' and beginning space exploration...I'm going to steer the topic back to something closer to the point of this thread:

Finding Defining 'Neighboring' Exoplanets

When I hear news about a new planet being found, or it being called "a nearby star," I believe there should be boundaries set as to what is truly a "nearby" or "neighboring" star/exoplanet.  They overuse the term and forget that, while correct on galactic scales, there's no way most of these star systems will ever be visited even with fantastic futuristic warp or hyper drives.  I'll clarify...

Let's start with the KIC 8462852 'alien megastructure ' planet.  It's 1500 light years away; distant enough that, barring a wormhole opening up, any would-be aliens would be unaware of our existence.  By contrast Epsilon Eridani, with its confirmed exoplanet, is roughly 11 light years away.  Epsilon is our next door neighbor, while KIC is all the way across town...if not in the next county.  Likewise Proxima, Alpha Centauri, and Sirius are all our true neighbors, with Vega and 47 Ursa Majoris being 'neighbors' from the next street away.

I bring this up because I find it bad comedy that we're finding exoplanets thousands of light years away (indeed an ancient one was even found inside a globular cluster) but we're barely aware of the inventory of worlds around stars our descendants will actually target.  Of course, it is simply the fact direct imaging, even with infrared, eludes us and our neighbors aren't all conveniently aligned for easy detection ala the Kepler mission.

I'd rather hear about how we're going to survey our immediate neighboring stars to find the first exoplanet we might attempt to visit.  Proxima is the most obvious.
Title: Re: Pale Red Dot
Post by: KelvinZero on 08/21/2016 02:09 am
I of all people don't think we need an exoplanet to become a multiplanetary species ("Occupy Mars"), but I definitely think a second Earth would be tremendously motivating for interstellar travel.
Yes absolutely. I don't think any enthusiasm this generates will be misdirected. For some reason the thought of a mission to our nearest neighbours does seem to focus public attention on hard SF concepts, goals we can actually connect to engineering principles of today.
Title: Re: Pale Red Dot
Post by: Star One on 08/21/2016 08:24 am
As much as I like the thought of humans going all 'Star Trek' and beginning space exploration...I'm going to steer the topic back to something closer to the point of this thread:

Finding Defining 'Neighboring' Exoplanets

When I hear news about a new planet being found, or it being called "a nearby star," I believe there should be boundaries set as to what is truly a "nearby" or "neighboring" star/exoplanet.  They overuse the term and forget that, while correct on galactic scales, there's no way most of these star systems will ever be visited even with fantastic futuristic warp or hyper drives.  I'll clarify...

Let's start with the KIC 8462852 'alien megastructure ' planet.  It's 1500 light years away; distant enough that, barring a wormhole opening up, any would-be aliens would be unaware of our existence.  By contrast Epsilon Eridani, with its confirmed exoplanet, is roughly 11 light years away.  Epsilon is our next door neighbor, while KIC is all the way across town...if not in the next county.  Likewise Proxima, Alpha Centauri, and Sirius are all our true neighbors, with Vega and 47 Ursa Majoris being 'neighbors' from the next street away.

I bring this up because I find it bad comedy that we're finding exoplanets thousands of light years away (indeed an ancient one was even found inside a globular cluster) but we're barely aware of the inventory of worlds around stars our descendants will actually target.  Of course, it is simply the fact direct imaging, even with infrared, eludes us and our neighbors aren't all conveniently aligned for easy detection ala the Kepler mission.

I'd rather hear about how we're going to survey our immediate neighboring stars to find the first exoplanet we might attempt to visit.  Proxima is the most obvious.

The multiple faulty predictions of the future in sci fi films and books of the past show that we are uniquely poor at the predicting our own future. And therefore I think there is no point in predicting what we will or will not do in the future technology wise.
Title: Re: Pale Red Dot
Post by: K-P on 08/21/2016 11:39 am
Let's start with the KIC 8462852 'alien megastructure ' planet.  It's 1500 light years away; distant enough that, barring a wormhole opening up, any would-be aliens would be unaware of our existence.  By contrast Epsilon Eridani, with its confirmed exoplanet, is roughly 11 light years away.  Epsilon is our next door neighbor, while KIC is all the way across town...if not in the next county.  Likewise Proxima, Alpha Centauri, and Sirius are all our true neighbors, with Vega and 47 Ursa Majoris being 'neighbors' from the next street away.

True, but such differences in various stellar distances are actually quite insignificant.

If we ever create starships able to travel 4 or 10 light years in a human lifetime, making a 1500-lightyear-trip is no big stretch.
We are talking about 200-fold distances then. It's like comparing bicycles and sports cars, or steam locomotives and space shuttles.
Sure, there's distance/velocity/technologies to gain but still, it's nothing exotic. You could go from East Coast to West Coast by bike or cross the Atlantic in a row boat. It just takes time. And technologies needed are at hand.

What is the big stretch here, is the initial interstellar trip. The first one.
At the moment we are so far away from that moment (timewise and technically) that it is not just a matter of time, it's a matter of technological revolution.

The closest stellar distances compared to let's say Voyager 1 at the moment are in the ballpark of 3 000 -fold.
That's no bike vs. car. That's no locomotive vs. space shuttle.
That's ant walking vs. Ferrari. Velocity AND technological level considered.

Once we manage first interstellar journeys a'la 10 lightyears, the rest is easy. Really easy.
Even entire galaxy is then easy.
Beyond that... well, I don't think we use tin cans to travel anymore by then but that's another topic.
Title: Re: Pale Red Dot
Post by: Lar on 08/21/2016 02:05 pm
was there ever an actual announcement? We seem to have veered off into feasibility of interstellar travel... not quite on topic.
Title: Re: Pale Red Dot
Post by: mfck on 08/21/2016 02:29 pm


...

The closest stellar distances compared to let's say Voyager 1 at the moment are in the ballpark of 3 000 -fold.
That's no bike vs. car. That's no locomotive vs. space shuttle.
That's ant walking vs. Ferrari. Velocity AND technological level considered.
...


An ant is FAR superior to a Ferrari, technology level wise (efficiency times complexity). The ant is a multipurpose, all-weather, self-guided, self replicating, massively redundant system. The Ferrari is a... car.

Just saying...
Title: Re: Pale Red Dot
Post by: Star One on 08/21/2016 02:42 pm
was there ever an actual announcement? We seem to have veered off into feasibility of interstellar travel... not quite on topic.

I imagine it will be sometime this week.
Title: Re: Pale Red Dot
Post by: as58 on 08/21/2016 04:41 pm
was there ever an actual announcement? We seem to have veered off into feasibility of interstellar travel... not quite on topic.

I imagine it will be sometime this week.

ESO press office (http://www.eso.org/public/events/press-evt/) says:
24 August 2016: Media Advisory: Press Conference at ESO HQ.

Curiously, they don't say anything about what the subject of the conference is...
Title: Re: Pale Red Dot
Post by: K-P on 08/21/2016 04:59 pm

An ant is FAR superior to a Ferrari, technology level wise (efficiency times complexity). The ant is a multipurpose, all-weather, self-guided, self replicating, massively redundant system. The Ferrari is a... car.

Just saying...

My bad.

Should have said "a Lamborghini" instead.

Now there's a dream with wheels, a missile with a steering wheel.

;)
Title: Re: Pale Red Dot
Post by: Star One on 08/21/2016 06:18 pm
was there ever an actual announcement? We seem to have veered off into feasibility of interstellar travel... not quite on topic.

I imagine it will be sometime this week.

ESO press office (http://www.eso.org/public/events/press-evt/) says:
24 August 2016: Media Advisory: Press Conference at ESO HQ.

Curiously, they don't say anything about what the subject of the conference is...

That kind of ties in with the secret Sky At Night just recorded and when the show is normally broadcast.
Title: Re: Pale Red Dot
Post by: baldusi on 08/22/2016 01:28 pm
An ant is FAR superior to a Ferrari, technology level wise (efficiency times complexity). The ant is a multipurpose, all-weather, self-guided, self replicating, massively redundant system. The Ferrari is a... car.

Just saying...
As an Italian,I find your lack of faith in the Cavallino Rampante very disturbing. I forbid you from eating pizza or pasta until you repent, wear red for one week and shout "Forza Ferrari" each time the Cavallino or a Formula One appears on TV. Should also make family lunch on Sundays and prepared "La pasta di la Nonna".  :P
Title: Re: Pale Red Dot
Post by: mfck on 08/22/2016 02:03 pm
An ant is FAR superior to a Ferrari, technology level wise (efficiency times complexity). The ant is a multipurpose, all-weather, self-guided, self replicating, massively redundant system. The Ferrari is a... car.

Just saying...
As an Italian,I find your lack of faith in the Cavallino Rampante very disturbing. I forbid you from eating pizza or pasta until you repent, wear red for one week and shout "Forza Ferrari" each time the Cavallino or a Formula One appears on TV. Should also make family lunch on Sundays and prepared "La pasta di la Nonna". 

"When they said REPENT REPENT
I wonder what they ment" ©
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/22/2016 02:19 pm
was there ever an actual announcement? We seem to have veered off into feasibility of interstellar travel... not quite on topic.

I imagine it will be sometime this week.

ESO press office (http://www.eso.org/public/events/press-evt/) says:
24 August 2016: Media Advisory: Press Conference at ESO HQ.

Curiously, they don't say anything about what the subject of the conference is...

At 1pm CET, 7am EDT apparently. ESO boss Tim de Zeeuw will be there.
Title: Re: Pale Red Dot
Post by: Lar on 08/22/2016 04:45 pm


An ant is FAR superior to a Ferrari, technology level wise (efficiency times complexity). The ant is a multipurpose, all-weather, self-guided, self replicating, massively redundant system. The Ferrari is a... car.

Just saying...
As an Italian,I find your lack of faith in the Cavallino Rampante very disturbing. I forbid you from eating pizza or pasta until you repent, wear red for one week and shout "Forza Ferrari" each time the Cavallino or a Formula One appears on TV. Should also make family lunch on Sundays and prepared "La pasta di la Nonna". 

"When they said REPENT REPENT
I wonder what they mean" ©

Settle down boys.
Title: Re: Pale Red Dot
Post by: Star One on 08/22/2016 07:40 pm
Article about the ESO announcement.

http://www.seeker.com/important-announcement-proxima-earth-like-exoplanet-1982234510.html
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/22/2016 09:29 pm
I realise it's not long now before we know for sure but one thing i'm confused about is why this is being hyped so much, certainly compared to the Alpha Centauri Bb announcement.  There was no live press conference at ESO HQ with the boss for that one, or special episodes of The Sky at Night etc as far as I remember, and i'm not sure the potential habitability angle can fully account for that.  You would think the opposite would be true, that'd they'd be more tentative, after the ACBb debacle.

...unless they are far more certain this time. The only conclusion I can come to is it must transit.  I wonder if TRAPPIST (Also at La Silla...) or one of the LCOGT scopes caught it?
Title: Re: Pale Red Dot
Post by: Bynaus on 08/22/2016 09:47 pm
I realise it's not long now before we know for sure but one thing i'm confused about is why this is being hyped so much, certainly compared to the Alpha Centauri Bb announcement.  There was no live press conference at ESO HQ with the boss for that one, or special episodes of The Sky at Night etc as far as I remember, and i'm not sure the potential habitability angle can fully account for that.  You would think the opposite would be true, that'd they'd be more tentative, after the ACBb debacle.

...unless they are far more certain this time. The only conclusion I can come to is it must transit.  I wonder if TRAPPIST (Also at La Silla...) or one of the LCOGT scopes caught it?

Or MOST? I agree - you usually don't walk into the same trap twice (hopefully), so I don't think this will (should!) be a RV-at-the-lower-limit-of-detection-type discovery as with Alpha Cen Bb. A transit would seem to be one possible explanation for the level of "institutional hype" we see here, but consider also that there was a microlensing campaign in April... A transit would still be the most exciting result because it means we could look at the composition of the atmosphere.

Also, a transit would reinforce my feeling that Elon wasn't completely wrong about the simulation argument - after all, the next century would be so much more interesting with a potentially habitable world at our interstellar doorstep! :)
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/22/2016 10:12 pm
Yeah there is the microlensing, though not as exciting as a transit as you say.  The only problem with MOST and the microlensing is that they are not related to ESO (except microlensing at Paranal, not La Silla), so why would the conference be there?  TRAPPIST is based at the La Silla facility and LCOGT was being operated in conjunction with the Pale Red Dot observations at HARPS which is why I suspect it could come from them.

Eugh, i'm not sure how much more waiting I can take.
Title: Re: Pale Red Dot
Post by: Star One on 08/22/2016 10:32 pm
Yeah there is the microlensing, though not as exciting as a transit as you say.  The only problem with MOST and the microlensing is that they are not related to ESO (except microlensing at Paranal, not La Silla), so why would the conference be there?  TRAPPIST is based at the La Silla facility and LCOGT was being operated in conjunction with the Pale Red Dot observations at HARPS which is why I suspect it could come from them.

Eugh, i'm not sure how much more waiting I can take.

Annoying isn't it all this waiting.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/22/2016 10:51 pm
There is a special place in hell for embargo leakers.
Title: Re: Pale Red Dot
Post by: Bubbinski on 08/23/2016 01:02 am
I will have a reason to be awake at 5 am Mountain on Wednesday. Will there be a webcast?
Title: Re: Pale Red Dot
Post by: CuddlyRocket on 08/23/2016 03:45 am
I notice that the IAUs Working Group on Star Names, which was set up this year to catalog and standardize proper names for stars, and which has stated that for the rest of 2016 it would focus on standardizing common names/spellings for the brightest few hundred stars with published names, has included Proxima Centauri (not one of those!) in its Catalog of Star Names updated on August 21. Almost as if they anticipated it being in the news! :)
Title: Re: Pale Red Dot
Post by: baldusi on 08/23/2016 04:10 am
Silly question, but does it has to be a transit or could they have used the radial velocity?
Title: Re: Pale Red Dot
Post by: Bynaus on 08/23/2016 05:17 am
@baldusi: well Pale Red Dot (PRD) was rv only. But it would be a detection at the high end of capabilities. So given the debacle with Alpha Cen Bb (where the situation was similar), Alpha_Centauri suggested that perhaps there was more to it. I think its absolutely possible that the PRD team contacted other groups which would have a shot at being helpful and who jumped at the occasion. Rv can tell you exactly when to look for a transit, so for a 30 day period planet this is an important piece of information (cannot just wait for it). And then its all about timing. I could imagine that a small telescope like MOST could make it. Well - we'll see tomorrow!
Title: Re: Pale Red Dot
Post by: Star One on 08/23/2016 06:48 am
@baldusi: well Pale Red Dot (PRD) was rv only. But it would be a detection at the high end of capabilities. So given the debacle with Alpha Cen Bb (where the situation was similar), Alpha_Centauri suggested that perhaps there was more to it. I think its absolutely possible that the PRD team contacted other groups which would have a shot at being helpful and who jumped at the occasion. Rv can tell you exactly when to look for a transit, so for a 30 day period planet this is an important piece of information (cannot just wait for it). And then its all about timing. I could imagine that a small telescope like MOST could make it. Well - we'll see tomorrow!

I suppose a planet in the habitable zone of a red dwarf is more likely to give you opportunities to catch a transit, very simply because it will cross the face of the star more often.
Title: Re: Pale Red Dot
Post by: Bynaus on 08/23/2016 07:14 am
Yes - that's why I wrote "30 days", but its actually a bit less, the orbital period of a Proxima planet in the HZ is between 3 and 15 days. For a solar type star, the recurrence time would be around a year (obviously). Also, transits of planets on short orbits are more likely for geometric reasons (because there is a larger range of inclinations that still lead to a transit).

But the point I was trying to make is that no-one will let their valuable space telescope stare at a star for 15 days just hoping to perhaps catch a transit. The intrinsic chance of transit is too low for that, even for a red dwarf (not saying it couldn't be done from a technical point of view, or that it hasn't ever been done before, just that it is uncommon). Especially if its a small object, and you need multiple transits to make out the signal. So getting a tip from a RV project when to stare at Proxima would be very valuable.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/23/2016 07:14 am
The geometric probability to transit for a habitable zone planet at Proxima is at most couple of percent. This is pretty large as transit probabilities go, but still far from certain it would transit. It would be a little spooky that the nearest star system just happened to be aligned correctly.
Title: Re: Pale Red Dot
Post by: K-P on 08/23/2016 07:43 am
The geometric probability to transit for a habitable zone planet at Proxima is a few percent. This is pretty large as transit probabilities go, but still far from certain it would transit. It would be a little spooky that the nearest star system just happened to be aligned correctly.

And yet, we are still unable to see Planet Nine (if it exists).
Let's hope that is also about to change.

Exciting times, exciting times...
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/23/2016 07:57 am
https://www.twitter.com/ESO/status/767859011198783488

Hmm
Title: Re: Pale Red Dot
Post by: Bynaus on 08/23/2016 09:10 am
The geometric probability to transit for a habitable zone planet at Proxima is a few percent. This is pretty large as transit probabilities go, but still far from certain it would transit. It would be a little spooky that the nearest star system just happened to be aligned correctly.

And yet, we are still unable to see Planet Nine (if it exists).
Let's hope that is also about to change.

Exciting times, exciting times...

I don't know if you are joking, but just in case you are not: we could absolutely see Planet Nine in reflected light - if we knew where to look. However, we have (currently) no chance to see the Pale Red Dot planet in reflected light, although we know exactly where to look. Our only chance with current instrumentation is the detection of the (tiny) radial velocity change the planet imparts on its star, the slight deflection of lensed starlight by the planet, or a transit, where the planet blocks a part of the light of its star (without actually being able to resolve the disk of the star or the planet transiting in front of it). Also, the Kepler telescope has found "Planet Nine"-like planets even at 1000s of light years - in transit.

But yes: exciting times! :)
Title: Re: Pale Red Dot
Post by: as58 on 08/23/2016 10:18 am
I realise it's not long now before we know for sure but one thing i'm confused about is why this is being hyped so much, certainly compared to the Alpha Centauri Bb announcement.  There was no live press conference at ESO HQ with the boss for that one, or special episodes of The Sky at Night etc as far as I remember, and i'm not sure the potential habitability angle can fully account for that. 

That's what I find surprising about this, too. They've really seemed to go out of their way to arrange all sorts of popular science stuff in connection with the announcement. Maybe it's just that I'm a jaded astronomer who isn't working on exoplanets, but what I've heard (in media and rumors from colleagues) doesn't seem to me quite that hypeworthy. Or maybe the juiciest details have been kept secret even from the usually very gossipy community.
Title: Pale Red Dot
Post by: Star One on 08/23/2016 11:14 am
I realise it's not long now before we know for sure but one thing i'm confused about is why this is being hyped so much, certainly compared to the Alpha Centauri Bb announcement.  There was no live press conference at ESO HQ with the boss for that one, or special episodes of The Sky at Night etc as far as I remember, and i'm not sure the potential habitability angle can fully account for that. 

That's what I find surprising about this, too. They've really seemed to go out of their way to arrange all sorts of popular science stuff in connection with the announcement. Maybe it's just that I'm a jaded astronomer who isn't working on exoplanets, but what I've heard (in media and rumors from colleagues) doesn't seem to me quite that hypeworthy. Or maybe the juiciest details have been kept secret even from the usually very gossipy community.

I believe you've answered your own question there. Have to feel there is more to this for them to be making such a fuss.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/23/2016 11:42 am
Hopefully; it wouldn't be the first overhyped announcement in astronomy though.

It just feels different to ACBb, which is odd.
Title: Re: Pale Red Dot
Post by: Oli on 08/23/2016 01:03 pm

I don't think we can expect anything but "Earth-sized planet in habitable zone". We won't know whether it's truly habitable for a long time to come.
Title: Re: Pale Red Dot
Post by: Star One on 08/23/2016 01:10 pm

I don't think we can expect anything but "Earth-sized planet in habitable zone". We won't know whether it's truly habitable for a long time to come.

Judging by name of the poster above you I think they may be the person to ask as regards habitability. Who knew that we had forum members from so far afield.
Title: Re: Pale Red Dot
Post by: Oli on 08/23/2016 02:10 pm

I don't think we can expect anything but "Earth-sized planet in habitable zone". We won't know whether it's truly habitable for a long time to come.

Judging by name of the poster above you I think they may be the person to ask as regards habitability. Who knew that we had forum members from so far afield.

Have we so far managed to analyze the atmosphere of Earth-sized planets?
Title: Re: Pale Red Dot
Post by: Hungry4info3 on 08/23/2016 07:49 pm
Looks like the hype was warranted. They have a very convincing paper, imho.

Quote
Have we so far managed to analyze the atmosphere of Earth-sized planets?
Depends on what you mean by analyze. We've got some constraints on the composition of the super-Earth at  55 Cnc (http://arxiv.org/abs/1606.08447v1) and GJ 1214 (http://arxiv.org/abs/1104.1173v1), but the only truly Earth-sized planets for which we have atmospheric constraints on are the inner two at TRAPPIST-1 (http://arxiv.org/abs/1606.01103v1), where we've determined only that they don't have a hydrogen envelope.
Title: Re: Pale Red Dot
Post by: Star One on 08/23/2016 07:51 pm

I don't think we can expect anything but "Earth-sized planet in habitable zone". We won't know whether it's truly habitable for a long time to come.

Judging by name of the poster above you I think they may be the person to ask as regards habitability. Who knew that we had forum members from so far afield.

Have we so far managed to analyze the atmosphere of Earth-sized planets?
It was obviously a very poor joke I was making.

Looks like the hype was warranted. They have a very convincing paper, imho.

Quote
Have we so far managed to analyze the atmosphere of Earth-sized planets?
Depends on what you mean by analyze. We've got some constraints on the composition of the super-Earth at  55 Cnc (http://arxiv.org/abs/1606.08447v1) and GJ 1214 (http://arxiv.org/abs/1104.1173v1), but the only truly Earth-sized planets for which we have atmospheric constraints on are the inner two at TRAPPIST-1 (http://arxiv.org/abs/1606.01103v1), where we've determined only that they don't have a hydrogen envelope.

You've seen it already.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/23/2016 07:56 pm
Some journalists have been tweeting they've seen it.


Oh and PRD just tweeted this,

https://twitter.com/Pale_red_dot/status/768174264201670657
Title: Re: Pale Red Dot
Post by: Hungry4info3 on 08/23/2016 08:13 pm
@baldusi: well Pale Red Dot (PRD) was rv only.
They also used quasi-simultaneous photometry to help make sure any RV signals they detected weren't caused by stellar activity.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/23/2016 08:37 pm
True, but strictly speaking only used to calibrate the RV rather than a separate detection method.

Or was it...?
Title: Re: Pale Red Dot
Post by: Star One on 08/23/2016 08:41 pm
I wonder if any microlensing was involved in this detection?
Title: Re: Pale Red Dot
Post by: Hungry4info3 on 08/23/2016 08:53 pm
Quote from: Alpha_Centauri
True, but strictly speaking only used to calibrate the RV rather than a seperate detection method. Or was it...?

Between those two options, I would say to calibrate. But they did search for transits.

Quote from: Star One
I wonder if any microlensing was involved in this detection?
No.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/23/2016 08:57 pm
Balls, that's no fun.  So an RV signal in the habitable zone, is that all the hype is about?  It's not like we could learn much more about it til someone gets round to building a big interferometer.
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/23/2016 10:38 pm
Balls, that's no fun.  So an RV signal in the habitable zone, is that all the hype is about?  It's not like we could learn much more about it til someone gets round to building a big interferometer.
I think you may underestimate the cleverness of motivated astronomers... JWST with sunshield, the 39m European Extremely Large Telescope, some of the huge interferometers we already have...
Title: Re: Pale Red Dot
Post by: Hungry4info3 on 08/23/2016 11:39 pm
It's important to realise that the Alf Cen system is so close that it really occupies a sort of unique regime of planet detectability. The technological requirements needed to directly image habitable planets in the system are fairly feasible compared to the overwhelming majority of nearby systems. Small coronographic missions have been proposed to do just this, such as ACESat (http://arxiv.org/abs/1510.02479).
Title: Re: Pale Red Dot
Post by: as58 on 08/24/2016 02:17 am
It's important to realise that the Alf Cen system is so close that it really occupies a sort of unique regime of planet detectability. The technological requirements needed to directly image habitable planets in the system are fairly feasible compared to the overwhelming majority of nearby systems. Small coronographic missions have been proposed to do just this, such as ACESat (http://arxiv.org/abs/1510.02479).

I don't think such a small telescope would cut it for Proxima, you need a very small inner working angle for that.  For Alpha Centauri A/B it's different.
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 02:50 am
was there ever an actual announcement? We seem to have veered off into feasibility of interstellar travel... not quite on topic.

I imagine it will be sometime this week.

ESO press office (http://www.eso.org/public/events/press-evt/) says:
24 August 2016: Media Advisory: Press Conference at ESO HQ.

Curiously, they don't say anything about what the subject of the conference is...

At 1pm CET, 7am EDT apparently. ESO boss Tim de Zeeuw will be there.
Is this going to be broadcast live? If so, does anyone have a link?

Is anyone there going to be live tweeting it, and if so, what is their Twitter handle?
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 03:28 am
By the way going just by diffraction limit (NOT by contrast ratio limits), the 39.3m E-ELT telescope should be capable of splitting the exoplanet from Proxima, to better than a factor of 10-20, if the planet is within the habitable zone. Of course, you've got that pesky atmosphere and a bright star, but it should be easier than a non-red-dwarf star.

And I think JWST should JUST be capable of doing the same.
Title: Re: Pale Red Dot
Post by: Star One on 08/24/2016 06:20 am
By the way going just by diffraction limit (NOT by contrast ratio limits), the 39.3m E-ELT telescope should be capable of splitting the exoplanet from Proxima, to better than a factor of 10-20, if the planet is within the habitable zone. Of course, you've got that pesky atmosphere and a bright star, but it should be easier than a non-red-dwarf star.

And I think JWST should JUST be capable of doing the same.

Unless I've misunderstood I was informed up thread that even if the JWST gets that free flying coronagraph it will not be much use in observing any potential planets.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/24/2016 06:44 am
Balls, that's no fun.  So an RV signal in the habitable zone, is that all the hype is about?  It's not like we could learn much more about it til someone gets round to building a big interferometer.
I think you may underestimate the cleverness of motivated astronomers... JWST with sunshield, the 39m European Extremely Large Telescope, some of the huge interferometers we already have...

I am not underestimating anything, none of those have much hope of directly imaging the planet.  JWST with starshade would have an inner working angle of about 100 mas, this means the planet would be blocked along with Proxima. The EELT cannot directly detect an earth-size planet that is at most 0.05 AU from Proxima; it might (Just!) be able to observe a giant planet at that distance, not an earth-size one, because of the contrast ratios.

There will be far more interesting targets coming along in the next few years from TESS, CHEOPS and PLATO than this planet, ones we can fully characterise.
Title: Re: Pale Red Dot
Post by: Bynaus on 08/24/2016 07:23 am
I was just wondering - if we do one day send a light sail towards Proxima - could we use it to temporarily cover the star from our point of view and, thereby, image the planet orbiting it? Has anyone ever studied this? If I am not mistaken, Proxima subtends an angle of about 0.04 arcsec. If the sail is, at, say, 100 AU, to subtend the same angle it would have to be 56 km wide (or 5.6 at 10 AU). Not too far from what one would want for a sail with a significant payload. Of course, there would also be the issue of positioning the telescope (or the sail) just right... (but perhaps this is not the right place for such a discussion?)
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/24/2016 07:34 am
Problem is if you intend to reach Proxima with a sail then your trajectory would likely not be along the line of sight.
Title: Re: Pale Red Dot
Post by: Star One on 08/24/2016 08:17 am
Balls, that's no fun.  So an RV signal in the habitable zone, is that all the hype is about?  It's not like we could learn much more about it til someone gets round to building a big interferometer.
I think you may underestimate the cleverness of motivated astronomers... JWST with sunshield, the 39m European Extremely Large Telescope, some of the huge interferometers we already have...

I am not underestimating anything, none of those have much hope of directly imaging the planet.  JWST with starshade would have an inner working angle of about 100 mas, this means the planet would be blocked along with Proxima. The EELT cannot directly detect an earth-size planet that is at most 0.05 AU from Proxima; it might (Just!) be able to observe a giant planet at that distance, not an earth-size one, because of the contrast ratios.

There will be far more interesting targets coming along in the next few years from TESS, CHEOPS and PLATO than this planet, ones we can fully characterise.

Pardon how can targets that are mostly likely to be further away than one that is on our doorstep.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/24/2016 08:43 am
It is the multitude of techniques we can bring to bare, rather than simple distance (as long as they are relatively nearby), that is the issue. If we find a nearby transiting planet in the habitable zone of a G-K dwarf we could learn far more about it than we could this planet by virtue of the fact we could pull out more varied information.

And for Direct Imaging a nearby habitable planet around a G-K dwarf would be more accessible to our current technology.
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 09:25 am
Balls, that's no fun.  So an RV signal in the habitable zone, is that all the hype is about?  It's not like we could learn much more about it til someone gets round to building a big interferometer.
I think you may underestimate the cleverness of motivated astronomers... JWST with sunshield, the 39m European Extremely Large Telescope, some of the huge interferometers we already have...

I am not underestimating anything, none of those have much hope of directly imaging the planet.  JWST with starshade would have an inner working angle of about 100 mas, this means the planet would be blocked along with Proxima. The EELT cannot directly detect an earth-size planet that is at most 0.05 AU from Proxima; it might (Just!) be able to observe a giant planet at that distance, not an earth-size one, because of the contrast ratios.

There will be far more interesting targets coming along in the next few years from TESS, CHEOPS and PLATO than this planet, ones we can fully characterise.
Yet if you are particularly motivated to image a certain target, can you not use very long integration times to enhance the contrast ratio, perhaps by stacking multiple exposures over the same spot in the planet's orbit?

Also, the star itself is very dim but the planet illuminated about typical, so the ratio in brightness between the red dwarf and the planet must be far less than typical.

Again, I suspect we'll see some exceeding cleverness be attempted to draw information out about Proxima Centauri b.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/24/2016 09:31 am
Oh I'm sure it'll be attempted, but it is certainly sub-optimal.  But at the moment I suspect more effort will go into the lower-hanging fruit from the new transit surveys.
Title: Re: Pale Red Dot
Post by: Star One on 08/24/2016 09:41 am
It is the multitude of techniques we can bring to bare, rather than simple distance (as long as they are relatively nearby), that is the issue. If we find a nearby transiting planet in the habitable zone of a G-K dwarf we could learn far more about it than we could this planet by virtue of the fact we could pull out more varied information.

And for Direct Imaging a nearby habitable planet around a G-K dwarf would be more accessible to our current technology.

That kind of statement is somewhat hostage to fortune considering the technology that it is likely to appear in the next twenty years.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/24/2016 09:48 am
You miss the point, It will not take twenty years to find other nearby planets we can study in more detail than this one.
Title: Re: Pale Red Dot
Post by: Star One on 08/24/2016 09:53 am
You miss the point, It will not take twenty years to find other nearby planets we can study in more detail than this one.

And you miss my point that with technology advancing your point will become mute and as the nearest target this planet will likely remain a priority.
Title: Re: Pale Red Dot
Post by: Bubbinski on 08/24/2016 11:07 am
ESO just tweeted they'll be making an announcement at 1900 hours CEST and to stay tuned until then. That should be 6 hours from now, or 11 am Mountain.
Title: Re: Pale Red Dot
Post by: Star One on 08/24/2016 11:18 am
ESO just tweeted they'll be making an announcement at 1900 hours CEST and to stay tuned until then. That should be 6 hours from now, or 11 am Mountain.

Oh so they've put it back for some reason. Thanks.
Title: Re: Pale Red Dot
Post by: jgoldader on 08/24/2016 11:20 am

Pardon how can targets that are mostly likely to be further away than one that is on our doorstep.

Proxima has 0.12 the Sun's mass but about 0.0017 the Sun's luminosity. So the habitable zone is much closer to the star than for a more massive star.  Imaging exoplanets is really tough because the contrast sucks (the reflected light from the planet is miniscule compared to the emitted light of the star) and the angular separation has to be well above the diffraction limit.  Even with a coronagraph, the point-spread function in the images has all kinds of asymmetries, and digging around in those looking for a planet's own light is a nasty mess.  So imaging an exoplanet very close to Proxima Cen would be somewhere between incredibly difficult and impossible, using current instrumentation.

This adds up to mean it would be easier to image a planet around a more luminous, more distant star, because the planet would be farther (in angular units) from the star, and easier to dig out of the mess a coronagraph leaves behind.  And no matter what, there's no telescope that could effectively resolve a planet around another star via direct imaging.  There have been conceptual designs floating around for years (the Terrestrial Planet Finder, for example) but all are beyond the state of the art of present technology.  Remember, there are Kuiper Belt objects in our own solar system that are ~1000 km across and are basically unresolved.  If you place them 200,000 times farther away, now you're getting a sense of how difficult resolving exoplanets will be.

I've heard nothing but what's been rumored here and a couple of other places, so the ongoing(?) presser may prove me wrong.  But I'd be surprised.
Title: Re: Pale Red Dot
Post by: as58 on 08/24/2016 11:35 am
ESO just tweeted they'll be making an announcement at 1900 hours CEST and to stay tuned until then. That should be 6 hours from now, or 11 am Mountain.

Oh so they've put it back for some reason. Thanks.

Apparently the press conference is on-going, but everything will be embargoed until 19:00 CEST. Which is kinda strange.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/24/2016 11:40 am
They've had all this time and they're going to release late evening for much of Europe? Genius.
Title: Pale Red Dot
Post by: Star One on 08/24/2016 11:43 am
ESO just tweeted they'll be making an announcement at 1900 hours CEST and to stay tuned until then. That should be 6 hours from now, or 11 am Mountain.

Oh so they've put it back for some reason. Thanks.

Apparently the press conference is on-going, but everything will be embargoed until 19:00 CEST. Which is kinda strange.

To catch the evening news I suppose. Wonder if that embargo will hold on social media.


Pardon how can targets that are mostly likely to be further away than one that is on our doorstep.

Proxima has 0.12 the Sun's mass but about 0.0017 the Sun's luminosity. So the habitable zone is much closer to the star than for a more massive star.  Imaging exoplanets is really tough because the contrast sucks (the reflected light from the planet is miniscule compared to the emitted light of the star) and the angular separation has to be well above the diffraction limit.  Even with a coronagraph, the point-spread function in the images has all kinds of asymmetries, and digging around in those looking for a planet's own light is a nasty mess.  So imaging an exoplanet very close to Proxima Cen would be somewhere between incredibly difficult and impossible, using current instrumentation.

This adds up to mean it would be easier to image a planet around a more luminous, more distant star, because the planet would be farther (in angular units) from the star, and easier to dig out of the mess a coronagraph leaves behind.  And no matter what, there's no telescope that could effectively resolve a planet around another star via direct imaging.  There have been conceptual designs floating around for years (the Terrestrial Planet Finder, for example) but all are beyond the state of the art of present technology.  Remember, there are Kuiper Belt objects in our own solar system that are ~1000 km across and are basically unresolved.  If you place them 200,000 times farther away, now you're getting a sense of how difficult resolving exoplanets will be.

I've heard nothing but what's been rumored here and a couple of other places, so the ongoing(?) presser may prove me wrong.  But I'd be surprised.

But surely such a discovery as this will give these kind of developments a push. The general public/politicians are going to be less interested in imaging exoplanets far away than ones very close at hand.
Title: Re: Pale Red Dot
Post by: frobnicat on 08/24/2016 11:54 am
Probably speaking out of ignorance here but wouldn't it make for a prime target on some hypothetically reachable solar (gravitational lens) focal mission at "only" 550AU ? Or maybe should such a mission be decided in some time, we'd likely knew some better characterized exoplanet (as alphacentauri says) as a better candidate, scientifically, than shot in the dark for a multibillion package... Just hoping that the symbolic impact of exoplanet "next door" can help build momentum toward this kind of ambitious observational missions.

Anyway, what kind of package would be needed at solar focal to resolve and do spectroscopy on this rumoured planet ? 50cm primary, less, way more ?
Title: Re: Pale Red Dot
Post by: jgoldader on 08/24/2016 12:40 pm

But surely such a discovery as this will give these kind of developments a push. The general public/politicians are going to be less interested in imaging exoplanets far away than ones very close at hand.

I guess, yeah, but physics is physics.  Me *wanting* to image continents on a putative Proxima Cen planet isn't going to change the physics of diffraction. Me *wanting* to get high resolution spectroscopy of the putative planet's putative atmosphere isn't going to make the technical difficulties of doing such any easier, or the price of doing so any less expensive.  I imagine the space-based interferometers likely needed to do such things will make JWST look like a cheap toy by comparison.

(And this weirdness of a press conference with delayed embargo sounds like a typical ESA PR fail.  What, are they trying to delay things until their TV special tonight?  Sigh.)
Title: Re: Pale Red Dot
Post by: as58 on 08/24/2016 12:56 pm
They've had all this time and they're going to release late evening for much of Europe? Genius.

Maybe they're going for the American audience...
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 01:17 pm
Is anyone else super excited about this? I woke up early for it, just to see the release postponed.

2016 is pretty awesome for big space announcements...
Title: Re: Pale Red Dot
Post by: Star One on 08/24/2016 02:09 pm
Is anyone else super excited about this? I woke up early for it, just to see the release postponed.

2016 is pretty awesome for big space announcements...

Me too. Does that make us sad space geeks?
Title: Re: Pale Red Dot
Post by: RonM on 08/24/2016 02:11 pm
Is anyone else super excited about this? I woke up early for it, just to see the release postponed.

2016 is pretty awesome for big space announcements...

Me too. Does that make us sad space geeks?

No, it makes us happy space geeks.  ;D
Title: Re: Pale Red Dot
Post by: rweede on 08/24/2016 03:31 pm
(And this weirdness of a press conference with delayed embargo sounds like a typical ESA PR fail.  What, are they trying to delay things until their TV special tonight?  Sigh.)

ESO is not ESA.
Title: Re: Pale Red Dot
Post by: jgoldader on 08/24/2016 04:14 pm
(And this weirdness of a press conference with delayed embargo sounds like a typical ESA PR fail.  What, are they trying to delay things until their TV special tonight?  Sigh.)

ESO is not ESA.

I know that, but a fail is a fail.
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 04:26 pm
Here's a link to the press conference: https://eso.adobeconnect.com/_a848728127/p3l3qqhq6un/?launcher=false&fcsContent=true&pbMode=normal
Title: Re: Pale Red Dot
Post by: CuddlyRocket on 08/24/2016 04:36 pm
Well, from the chat bar on the side, it appears that there's one planet 'candidate' that they've designated Proxima b.
Title: Re: Pale Red Dot
Post by: Star One on 08/24/2016 04:39 pm
Quote
Pale Red Dot –  ‏@Pale_red_dot

UPDATE 1/11: #palereddot aim was to look for an Earth-like planet around #ProximaCentauri  https://palereddot.org/launch/

https://mobile.twitter.com/Pale_red_dot/status/768486825996521472
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 04:40 pm
https://twitter.com/Pale_red_dot/status/768486825996521472
Pale Red Dot
‏@Pale_red_dot
Quote
UPDATE 1/11: #palereddot aim was to look for an Earth-like planet around #ProximaCentauri https://palereddot.org/launch/

EDIT:Ninja'd, but here's the video of that link:
https://www.youtube.com/watch?v=5wHldZgb7nI
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 04:42 pm
Pale Red Dot ‏@Pale_red_dot  1m1 minute ago
https://twitter.com/Pale_red_dot/status/768488181922758656
Quote
2/11 #ProximaCentauri is an M-Dwarf located 4.24 lightyears from Earth - it is the closest star to the Solar System! #palereddot
Title: Re: Pale Red Dot
Post by: CuddlyRocket on 08/24/2016 04:42 pm
Mass 1.3xEarth, period 11.2 days, distance 0.05 AU, irradiance 65% of Earth, temp ~235 K.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/24/2016 04:43 pm
Well, from the chat bar on the side, it appears that there's one planet 'candidate' that they've designated Proxima b.

Yes, the paper says 'candidate' too which I found odd. If they have an RV mass then it shouldn't be a 'candidate'.
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 04:45 pm
Mass 1.3xEarth, period 11.2 days, distance 0.05 AU, irradiance 65% of Earth, temp ~235 K.
Good. I'd prefer it slightly on the cold side, since such a large planet may have a larger atmosphere and thus a greater greenhouse effect than Earth.
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 04:47 pm
https://twitter.com/Pale_red_dot/status/768489265235890176
Pale Red Dot ‏@Pale_red_dot  2m2 minutes ago
Quote
3/11 #ProximaCentauri  has been monitored for 16 years, with no success of finding a planet
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 04:48 pm
https://twitter.com/Pale_red_dot/status/768489895048413184
Pale Red Dot
‏@Pale_red_dot
Quote
4/11 However there were hints of a signal between 10-20 days https://palereddot.org/the-signal/  #palereddot
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 04:51 pm
https://twitter.com/Pale_red_dot/status/768490841837109252
Pale Red Dot
‏@Pale_red_dot
Quote
5/11 #palereddot observed #ProximaCentauri for 60 nights in a row with HARPS, ASH2 and @lcogt
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 04:54 pm
https://twitter.com/Pale_red_dot/status/768491574615535616
6/11 #palereddot had a 90% success rate (54/60 nights) thanks to very good weather!!
Title: Re: Pale Red Dot
Post by: Mongo62 on 08/24/2016 04:54 pm
Mass 1.3xEarth, period 11.2 days, distance 0.05 AU, irradiance 65% of Earth, temp ~235 K.

235C is about 20C colder than Earth. However, Earth appears to be right on the inner edge of the Sun's habitable zone, while an effective temperature of 235C would be right in the middle of even a conservative HZ.

Plus as Robotbeat says, the planet is slightly more massive than the Earth, so most likely has a thicker atmosphere due to greater geological activity and a deeper gravity well, and so should have a greater greenhouse effect raising average surface temperatures.

The thicker atmosphere would also (I assume) allow better redistribution of heat from the "day" hemisphere to the "night" hemisphere.
Title: Re: Pale Red Dot
Post by: Star One on 08/24/2016 04:57 pm
Mass 1.3xEarth, period 11.2 days, distance 0.05 AU, irradiance 65% of Earth, temp ~235 K.

235C is about 20C colder than Earth. However, Earth appears to be right on the inner edge of the Sun's habitable zone, while an effective temperature of 235C would be right in the middle of even a conservative HZ.

Plus as Robotbeat says, the planet is slightly more massive than the Earth, so most likely has a thicker atmosphere due to greater geological activity and a deeper gravity well, and so should have a greater greenhouse effect raising average surface temperatures.

The thicker atmosphere would also (I assume) allow better redistribution of heat from the "day" hemisphere to the "night" hemisphere.

It could more like be Venus 2 than anything.
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 04:59 pm
7/11 #palereddot observations of #ProximaCentauri find a signal that is consistent with previous 16 years of data.
https://twitter.com/Pale_red_dot/status/768492353896275969
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 05:00 pm
8/11 #palereddot team confirm the Doppler signal and are sure it is not caused by activity on #ProximaCentauri
https://twitter.com/Pale_red_dot/status/768492846710190081
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 05:02 pm
Nature journal cover... :)
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 05:02 pm
9/11 #palereddot  data is best interpreted by the presence of a planet
https://twitter.com/Pale_red_dot/status/768493491366354944

10/11 A #terrestrial #planet with an orbital period of 11.2 days and an M sin I of 1.3 Earth masses
https://twitter.com/Pale_red_dot/status/768493573016784896
Title: Pale Red Dot
Post by: Star One on 08/24/2016 05:03 pm
First article I've seen.

Rocky planet found orbiting habitable zone of nearest star

http://phys.org/news/2016-08-rocky-planet-orbiting-habitable-zone.amp

You'll find various media materials on the link including video.
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 05:03 pm
11/11 #ProximaCentauri  HAS A TERRESTRIAL PLANET ORBITING IN ITS #HABITABLE ZONE! #palereddot
https://twitter.com/Pale_red_dot/status/768493931130531840
Title: Re: Pale Red Dot
Post by: Orbiter on 08/24/2016 05:06 pm
Proxima Centauri b:

M: 1.3x Earth masses.
Orbital Period: 11.2 days.
Planet type: Terrestrial
Habitable zone: Yes!

Simply amazing!
Title: Re: Pale Red Dot
Post by: CuddlyRocket on 08/24/2016 05:08 pm
Daily Mail article. (http://www.dailymail.co.uk/sciencetech/article-3756479/The-second-Earth-visit-lifetime-Planet-discovered-just-four-light-years-away-scientists-say-liquid-water-alien-life.html?ito=social-twitter_mailonline)

Interesting (to me, anyway!) that they've designated (not named, that will probably come after it's confirmed) it Proxima b. Technically you should take one of its catalogue designations (Alpha Centauri C, GJ 551, etc) and add a lower-case b, but it's common informal usage to use a star's proper name and add a b. Of course, the star's name is Proxima Centauri, but I just knew they'd shorten it - and as it's informal usage anyway, why not? :)
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 05:12 pm
https://twitter.com/Pale_red_dot/status/768495259852701696
Quote
Check out this awesome video from @ESO showing the results and amazing imagesPale Red Dot added,
ESO @ESO
Quote
#ESOcast 87 presents the #PaleRedDot results
http://socsi.in/IfZxG
Title: Re: Pale Red Dot
Post by: Star One on 08/24/2016 05:13 pm
https://www.youtube.com/watch?v=aOTWo6_602Q
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 05:15 pm
https://twitter.com/ESO/status/768495067157917696
ESO ‏@ESO  6m6 minutes ago
Quote
A replay of the press conference today on #Proximab #PaleRedDot is available here: http://socsi.in/fau5v
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/24/2016 05:24 pm
Pale Red Dot ‏@Pale_red_dot  4m4 minutes ago
@ESO artist impression of the terrestrial planet #proximab #palereddot
https://twitter.com/Pale_red_dot/status/768498247841247232
Title: Re: Pale Red Dot
Post by: Star One on 08/24/2016 05:34 pm
Here's the Nature paper.

http://www.nature.com/nature/journal/v536/n7617/full/nature19106.html
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/24/2016 05:47 pm
^^^^ Without paywall

http://www.eso.org/public/archives/releases/sciencepapers/eso1629/eso1629a.pdf
Title: Re: Pale Red Dot
Post by: JasonAW3 on 08/24/2016 06:04 pm
[
Plus as Robotbeat says, the planet is slightly more massive than the Earth, so most likely has a thicker atmosphere due to greater geological activity and a deeper gravity well, and so should have a greater greenhouse effect raising average surface temperatures.


There is, however, the remote possibility that Proxima b may actually be a binary, much like the Earth and moon are. If so, they may have a similar rotation arrangement to Earth and the Moon, or they could be spinning around each other at just above the Roche Limit.  We won't really know until we can get a better look at it.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/24/2016 06:18 pm
Mass 1.3xEarth, period 11.2 days, distance 0.05 AU, irradiance 65% of Earth, temp ~235 K.

I would point out that 1.3xEarth mass is the minimum mass, or MsinI. They do not know I and so cannot tell the true mass.
Title: Re: Pale Red Dot
Post by: as58 on 08/24/2016 06:21 pm
Mass 1.3xEarth, period 11.2 days, distance 0.05 AU, irradiance 65% of Earth, temp ~235 K.

That mass is actually M sin i as usual of radial velocity planet detections. True mass can't be determined without knowing the inclination.

Edit: As said above a bit earlier.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/24/2016 06:21 pm
Ninja'd

Oh, interestingly the project lead says they are still checking for transits. *fingers crossed*
Title: Re: Pale Red Dot
Post by: gosnold on 08/24/2016 06:25 pm
Mass 1.3xEarth, period 11.2 days, distance 0.05 AU, irradiance 65% of Earth, temp ~235 K.

I would point out that 1.3xEarth mass is the minimum mass, or MsinI. They do not know I and so cannot tell the true mass.

One of the scientist on the webcast said it was likely close to the minimum mass, based on Kepler data and planet formation models.
Title: Re: Pale Red Dot
Post by: as58 on 08/24/2016 06:26 pm
Anyone know if it should have already been detected if it's transiting? If so, that would give some sort of (weak) upper limit for inclination.

Edit: After reading the paper, apparently transits wouldn't have been necessarily detected before.
Title: Re: Pale Red Dot
Post by: high road on 08/24/2016 06:34 pm
https://www.youtube.com/watch?v=aOTWo6_602Q

Even the closest star has a planet in the habitable zone, and being so close is what allowed us to detected? That's as impressive as a statistic can be.

Centaur-eye? IIRC, every sci-fi movie I ever saw pronounced it as centaur-ee. As in the Gemini programme.

And after they've determined whether there's oxygen on the planet, how long would it take for a small probe to get there to determine whether there are 12 feet tall blue locals? Any chance our children would get to see that? Or would even a small probe be hard to accelerate to such speeds?
Title: Re: Pale Red Dot
Post by: Star One on 08/24/2016 06:34 pm
Ninja'd

Oh, interestingly the project lead says they are still checking for transits. *fingers crossed*

Apparently HARPS may have some tricks up their collective sleeves.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 08/24/2016 06:43 pm
Anyone know if it should have already been detected if it's transiting? If so, that would give some sort of (weak) upper limit for inclination.

Edit: After reading the paper, apparently transits wouldn't have been necessarily detected before.

Oh, a little cold water on that front from the MOST team;

http://www.ifweassume.com/2016/08/flares-on-proxima-cen.html

https://dl.dropboxusercontent.com/u/47240764/davenport_proxima_flares.pdf
Quote
we show that flares with flux amplitudes of 0.5%[the size of an earth-size planet] occur 63 times per day

It's gonna be HARD.
Title: Re: Pale Red Dot
Post by: Star One on 08/24/2016 06:44 pm
Yes it maybe a difficult and possibly dead target but it could still inspire humanity.

http://blogs.scientificamerican.com/life-unbounded/proxima-centauri-just-became-our-gateway-to-the-cosmos/
Title: Re: Pale Red Dot
Post by: Bubbinski on 08/24/2016 06:49 pm
So it is "really real"...that is HUGE.

As far as the star's flare activity and question of habitability goes, would the fact that it's at least 1.3 earth masses make it more likely to have a protective magnetic field than if it were smaller? Regardless I'm looking forward to future discoveries (and even sci-fi writings) about this world. Let's get cracking on mega-ginormous space telescopes and Starshot-like stellar probes!
Title: Pale Red Dot
Post by: Star One on 08/24/2016 06:59 pm
A couple of members of Project Starshot interviewed about this discovery.

http://www.sci-news.com/astronomy/proxima-b-exoplanet-habitable-zone-04130.html

Will this planet be giving an official name by the IAU because it's so close?

Pale Red Dot Reddit

https://m.reddit.com/r/askscience/comments/4zdkra/askscience_ama_series_we_have_discovered_an/?platform=hootsuite&utm_source=mweb_redirect&compact=true

This article is claiming that E-ELT should be possible to image it directly?

http://www.bbc.co.uk/news/science-environment-37167390
Title: Re: Pale Red Dot
Post by: CuddlyRocket on 08/24/2016 08:02 pm
Oh, interestingly the project lead says they are still checking for transits. *fingers crossed*

Apparently HARPS may have some tricks up their collective sleeves.

Presumably, you can use the radial velocity measurements to determine when the planet would be transiting (basically at the time the star's velocity switches from receding to approaching) thereby enabling you to disregard most of the fluctuations in the data?


Will this planet be giving an official name by the IAU because it's so close?

Almost certainly, but probably not until it's confirmed by an independent team. Possibly by the public via another NameExoWorlds campaign.
Title: Re: Pale Red Dot
Post by: Joffan on 08/24/2016 08:02 pm
OK I'm going to have a little moan about that nature video, even as I thank you for passing it on to us. In particular about the cartoon of the sun-planet orbit effects and the Doppler shift illustration.

The star is shown as getting pulled out of position by the planet. Wrong. The star and planet both orbit around their common barycentre, so when the planet is coming towards us the star is going away; when the planet is close the star is fractionally further away than usual, etc.

The Doppler shift is illustrated, wrongly, as dependent on distance, rather than movement. The blue phase should be as the star is moving (ever so slightly) towards us, not when it is closest to us, and likewise the red shift is on its retreat from us.
Title: Re: Pale Red Dot
Post by: Bynaus on 08/24/2016 08:33 pm
Oh wow. Just as we start to figure out how to re-use rockets and go to Mars, someone puts up the next carrot... :)

There is, however, the remote possibility that Proxima b may actually be a binary, much like the Earth and moon are. If so, they may have a similar rotation arrangement to Earth and the Moon, or they could be spinning around each other at just above the Roche Limit.  We won't really know until we can get a better look at it.

Sorry for the bucket of cold water, but this is not actually an option. Proxima would lock the planet nevertheless, and the satellite would then be pulled down (as the locked planet now rotates solver than the satellite revolves) to the point where it is destroyed at the Roche limit (actually, this would all happen in lockstep, as the star slows down the planet, the satellite is reeled in). Also, the Hill-sphere of Proxima b is only about 110'000 km wide (at the planet's minimum mass), so a satellite would have to be much closer than the Moon anyway.

The only option how a red dwarf planet in the HZ does not need to enter tidal lock or some other kind of despun state (like Venus) is that it orbits a gas giant (think Asimov's "Nemesis" planet).
Title: Pale Red Dot
Post by: Star One on 08/24/2016 08:39 pm
Oh wow. Just as we start to figure out how to re-use rockets and go to Mars, someone puts up the next carrot... :)

There is, however, the remote possibility that Proxima b may actually be a binary, much like the Earth and moon are. If so, they may have a similar rotation arrangement to Earth and the Moon, or they could be spinning around each other at just above the Roche Limit.  We won't really know until we can get a better look at it.

Sorry for the bucket of cold water, but this is not actually an option. Proxima would lock the planet nevertheless, and the satellite would then be pulled down (as the locked planet now rotates solver than the satellite revolves) to the point where it is destroyed at the Roche limit (actually, this would all happen in lockstep, as the star slows down the planet, the satellite is reeled in). Also, the Hill-sphere of Proxima b is only about 110'000 km wide (at the planet's minimum mass), so a satellite would have to be much closer than the Moon anyway.

The only option how a red dwarf planet in the HZ does not need to enter tidal lock or some other kind of despun state (like Venus) is that it orbits a gas giant (think Asimov's "Nemesis" planet).

But then there's resonate rotation, transferring heat around the planet more effectively.

https://mobile.twitter.com/ROGAstronomers/status/768500010321338368
Title: Re: Pale Red Dot
Post by: redliox on 08/24/2016 08:45 pm
I'm delighted to hear about our nearest neighbor!  ;D
Makes me all the more glad I put this thread up when I did!  ;)

I will admit I thought the prospects of an Earthlike planet were dim, but naturally neither opinions or theories are absolute...and apparently Proxima has planets.  For anyone interested in red dwarfs with planetary systems...well now there's a giant target (of a small star) just outside our backyard.

There's some mentions of a possibility of a 2nd planet, although it's unconfirmed.  Space.com's article made a paragraph mentioning signs implying it would be orbiting around 60 to 500 days, certainly well outside the habitable zone the confirmed planet occupies.  Inclusive for the moment, but looking at other systems discovered by Kepler along with other telescopes, there are many cases of planets sized from Mars to Neptune in tight orbits.  There likely may be sibling planets nearby.  There aren't any large outer planets, and I wouldn't be surprised if interactions with Alpha Centauri A & B ripped those away; but a compact system near Proxima certainly would have remained intact.

I sincerely hope this draws attentions to our immediate neighbors; I'd like to see a requirement for the next large space telescope to be able to directly image this world.
Title: Pale Red Dot
Post by: Star One on 08/24/2016 08:49 pm
I'm delighted to hear about our nearest neighbor!  ;D
Makes me all the more glad I put this thread up when I did!  ;)

I will admit I thought the prospects of an Earthlike planet were dim, but naturally neither opinions or theories are absolute...and apparently Proxima has planets.  For anyone interested in red dwarfs with planetary systems...well now there's a giant target (of a small star) just outside our backyard.

There's some mentions of a possibility of a 2nd planet, although it's unconfirmed.  Space.com's article made a paragraph mentioning signs implying it would be orbiting around 60 to 500 days, certainly well outside the habitable zone the confirmed planet occupies.  Inclusive for the moment, but looking at other systems discovered by Kepler along with other telescopes, there are many cases of planets sized from Mars to Neptune in tight orbits.  There likely may be sibling planets nearby.  There aren't any large outer planets, and I wouldn't be surprised if interactions with Alpha Centauri A & B ripped those away; but a compact system near Proxima certainly would have remained intact.

I sincerely hope this draws attentions to our immediate neighbors; I'd like to see a requirement for the next large space telescope to be able to directly image this world.

Thank you for answering the question about the possibility of it being a compact solar system.

It wouldn't surprise me if the binary pair have a solar system as well, maybe they've stolen planets off each other?
Title: Re: Pale Red Dot
Post by: Orbiter on 08/24/2016 09:00 pm
The Pale Red Dot team is doing a Reddit AMA right now. Found this tidbit interesting (and unsurprising as one would think most solar systems have more than one planet):

Quote
Q. My question is, since stars like our own and many others in the galaxy are usually accompanied by multiple planets, Is there a possibility of another planet orbiting Proxima Centauri?

Quote
A. Our data contained a secondary signal at a longer period but our campaign didn't last long enough to confirm it. We will probably have to run another campaign to check that one out.
Title: Pale Red Dot
Post by: Star One on 08/24/2016 09:08 pm
Also saw this comment online that the long rotation period of Proxima, planets love to rob angular momentum from stars and therefore it's likely there are more planets in this system.
Title: Re: Pale Red Dot
Post by: Skamp_X on 08/24/2016 09:21 pm
Wish granted!
Always hoped they would find atleast 1 planet in the alpha centauri system (including proxima),
simply because its the closest star system.
With the distances involved in interstellar flight, we need something to motivate us,
to hopefully , eventualy , give it a shot at sending something to take a closer look.
I know flying over there is a different story, but if the nearest star with a interesting planet was 20ly away,
it might take a long time before we ever consider doing it for real, atleast 4,2ly might be tempting to try it sooner  :)
Title: Re: Pale Red Dot
Post by: Star One on 08/24/2016 09:23 pm
I want to see Barnard's star examined again next.
Title: Re: Pale Red Dot
Post by: Blackstar on 08/24/2016 10:36 pm
Title: Re: Pale Red Dot
Post by: Hungry4info3 on 08/24/2016 11:21 pm
Regarding the efforts to image the planet, here's a simulation of a detection of a ~HZ terrestrial planet at Proxima Centauri with E-ELT.

http://adsabs.harvard.edu/abs/2015A%26A...576A..59S
Title: Re: Pale Red Dot
Post by: Mongo62 on 08/25/2016 01:45 am
Exploring plausible formation scenarios for the planet candidate orbiting Proxima Centauri (http://arxiv.org/abs/1608.06908)

We present a study of 4 different formation scenarios that may explain the origin of the recently announced planet `Proxima b' orbiting the star Proxima Centauri. The aim is to examine how the formation scenarios differ in their predictions for the multiplicity of the Proxima planetary system, the water/volatile content of Proxima b and its eccentricity, so that these can be tested by future observations. A scenario of in situ formation via giant impacts from a locally enhanced disc of planetary embryos and planetesimals, predicts that Proxima b will be a member of a multiplanet system with a measurably finite value of orbital eccentricity. Assuming that the local solid enhancement needed to form a Proxima b analogue with a minimum mass of 1.3 Earth masses arises because of the inwards drift of solids in the form of small planetesimals/boulders, this scenario also likely results in Proxima b analogues that are moderately endowed with water/volatiles, arising from the dynamical diffusion of icy planetesimals from beyond the snowline during planetary assembly. A scenario in which multiple embryos form, migrate and mutually collide within a gaseous protoplanetary disc also results in Proxima b being a member of a multiple system, but where its members are Ocean planets due to accretion occurring mainly outside of the snowline, possibly within mean motion resonances. A scenario in which a single accreting embryo forms at large distance from the star, and migrates inwards while accreting either planetesimals/pebbles results in Proxima b being an isolated Ocean planet on a circular orbit. A scenario in which Proxima b formed via pebble accretion interior to the snowline produces a dry planet on a circular orbit. Future observations that characterise the physical/orbital properties of Proxima b, and the multiplicity of the system, will provide valuable insight into its formation history.

The Habitability of Proxima Centauri b I: Evolutionary Scenarios (http://arxiv.org/abs/1608.06919)

We analyze the evolution of the potentially habitable planet Proxima Centauri b to identify environmental factors that affect its long-term habitability. We consider physical processes acting on size scales ranging between the galactic scale, the scale of the stellar system, and the scale of the planet's core. We find that there is a significant probability that Proxima Centauri has had encounters with its companion stars, Alpha Centauri A and B, that are close enough to destabilize Proxima Centauri's planetary system. If the system has an additional planet, as suggested by the discovery data, then it may perturb planet b's eccentricity and inclination, possibly driving those parameters to non-zero values, even in the presence of strong tidal damping. We also model the internal evolution of the planet, evaluating the roles of different radiogenic abundances and tidal heating and find that a planet with chondritic abundance may not generate a magnetic field, but all other models do maintain a magnetic field. We find that if planet b formed in situ, then it experienced ~160 million years in a runaway greenhouse as the star contracted during its formation. This early phase may have permanently desiccated the planet and/or produced a large abiotic oxygen atmosphere. On the other hand, if Proxima Centauri b formed with a thin hydrogen atmosphere (<1% of the planet's mass), then this envelope could have shielded the water long enough for it to be retained before being blown off itself. Through modeling a wide range of Proxima b's evolutionary processes we identify pathways for planet b to be habitable and conclude that water retention is the biggest obstacle for planet b's habitability. These results are all obtained with a new software package called VPLANET.

The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present (http://arxiv.org/abs/1608.06813)

Proxima b is a planet with a minimum mass of 1.3 MEarth orbiting within the habitable zone (HZ) of Proxima Centauri, a very low-mass, active star and the Sun's closest neighbor. Here we investigate a number of factors related to the potential habitability of Proxima b and its ability to maintain liquid water on its surface. We set the stage by estimating the current high-energy irradiance of the planet and show that the planet currently receives 30 times more EUV radiation than Earth and 250 times more X-rays. We compute the time evolution of the star's spectrum, which is essential for modeling the flux received over Proxima b's lifetime. We also show that Proxima b's obliquity is likely null and its spin is either synchronous or in a 3:2 spin-orbit resonance, depending on the planet's eccentricity and level of triaxiality. Next we consider the evolution of Proxima b's water inventory. We use our spectral energy distribution to compute the hydrogen loss from the planet with an improved energy-limited escape formalism. Despite the high level of stellar activity we find that Proxima b is likely to have lost less than an Earth ocean's worth of hydrogen before it reached the HZ 100-200 Myr after its formation. The largest uncertainty in our work is the initial water budget, which is not constrained by planet formation models. We conclude that Proxima b is a viable candidate habitable planet.

The habitability of Proxima Centauri b II. Possible climates and Observability (http://arxiv.org/abs/1608.06827)

Radial velocity monitoring has found the signature of a Msini=1.3~M⊕ planet located within the Habitable Zone of Proxima Centauri, (Anglada-Escud\'e et al. 2016). Despite a hotter past and an active host star the planet Proxima~b could have retained enough volatiles to sustain surface habitability (Ribas et al. 2016).

Here we use a 3D Global Climate Model to simulate Proxima b's atmosphere and water cycle for its two likely rotation modes (1:1 and 3:2 resonances) while varying the unconstrained surface water inventory and atmospheric greenhouse effect.

We find that a broad range of atmospheric compositions can allow surface liquid water. On a tidally-locked planet with a surface water inventory larger than 0.6 Earth ocean, liquid water is always present, at least in the substellar region. Liquid water covers the whole planet for CO2 partial pressures ≳1~bar. For smaller water inventories, water can be trapped on the night side, forming either glaciers or lakes, depending on the amount of greenhouse gases. With a non-synchronous rotation, a minimum CO2 pressure is required to avoid falling into a completely frozen snowball state if water is abundant. If the planet is dryer, ∼0.5~bar of CO2 would suffice to prevent the trapping of any arbitrary small water inventory into polar ice caps. More generally, any low-obliquity planet within the classical habitable zone of its star should be in one of the climate regimes discussed here.

We use our GCM to produce reflection/emission spectra and phase curves. We find that atmospheric characterization will be possible by direct imaging with forthcoming large telescopes thanks to an angular separation of 7λ/D at 1~μm (with the E-ELT) and a contrast of ∼10−7. The magnitude of the planet will allow for high-resolution spectroscopy and the search for molecular signatures.
Title: Re: Pale Red Dot
Post by: hop on 08/25/2016 05:17 am
A nice video form David Kipping, who is on the team looking for transits with MOST
https://www.youtube.com/watch?v=tcc635lNRwY

Short version: They are still analyzing the data, expect results in a few weeks. They did release a paper on flare activity today "MOST Observations of our Nearest Neighbor: Flares on Proxima Centauri" http://arxiv.org/abs/1608.06672

They also hosted a video from Guillem Anglada of the Pale Red Dot team:
https://www.youtube.com/watch?v=59ClESB1AqA

Title: Re: Pale Red Dot
Post by: Ben the Space Brit on 08/25/2016 06:32 am
I note that Proxima is pretty small, even for red dwarves. It may be interesting to see just how much of a radiation hazard there is that close in to such a low-output object.

Optimistically, if the possible Proxima-C is a large body, then we might have a Galilean Moon scenario where there are several close-orbiting bodies whose resonating orbits mean that they all add tidal heating to their interior heat and this increases the likelihood of some form of magnetic field. This is offset by the high likelihood that Proxima is a captured object rather than native to Alpha-A and -B's natal star group; as red dwarves tend to be long-lived, the system may be much older than Sol.

At the very least Proxima-B lies firmly in a 'worth a look' category. I would suspect that it could be plausibly reached by a light sail, nuclear thermal or nuclear electric propulsion probe within a Voyager 1-type duration mission (30 years). Time to send flagship mission proposals to NASA?
Title: Pale Red Dot
Post by: Star One on 08/25/2016 06:49 am
Does anyone know if Alpha Centauri A & B are actively being studied for exoplanets at this time? As they would be easier to observe I would imagine with the habitable zone being further out from the stars.
Title: Re: Pale Red Dot
Post by: Ben the Space Brit on 08/25/2016 06:51 am
AFAIK, there is some evidence that A-Centauri-B has a 'Hot Jupiter' but the evidence has been challenged by some in the field.

The problem is that Alpha-A and -B are in a fairly close orbit. It has a period of 80 years and the closest approach is about Saturn's mean distance from the Sun. Because of this, only close-orbiting and lower-mass worlds would have avoided being ejected from the system by gravitational interactions.

Theoretical modelling suggest that an Earth-mass planet in Alpha-A's habitable zone is possible. However, detecting a small object in a 350-400 day orbit around such a heavy and bright object would be a bit challenging unless there was a conveniently-observed transit.
Title: Pale Red Dot
Post by: Star One on 08/25/2016 06:56 am
AFAIK, there is some evidence that A-Centauri-B has a 'Hot Jupiter' but the evidence has been challenged by some in the field.

I probably should have qualified my question to say outside of that challenged result?

I would think if you're looking for Earth analogues that A would be better than B as isn't B though similar in size to Sun also cooler?

But as you've added the big problem is they are closely orbiting binary pair.
Title: Re: Pale Red Dot
Post by: Hungry4info3 on 08/25/2016 07:01 am
The falsified (http://arxiv.org/abs/1510.05598) planet detection for Alf Cen B was a hot ~Earth-mass planet (http://www.nature.com/nature/journal/v491/n7423/full/nature11572.html), not a hot Jupiter.

Regarding A vs B, the B star is more RV-stable (K-type stars are a sort of sweet spot for RV, with a decent balance between brightness, rotational velocity, and spectral line availability. Also being cooler, Alf Cen B's HZ is closer in, making the planet more dynamically stable than an HZ planet around Alf Cen A.
Title: Re: Pale Red Dot
Post by: Star One on 08/25/2016 07:07 am
The falsified (http://arxiv.org/abs/1510.05598) planet detection for Alf Cen B was a hot ~Earth-mass planet (http://www.nature.com/nature/journal/v491/n7423/full/nature11572.html), not a hot Jupiter.

Regarding A vs B, the B star is more RV-stable (K-type stars are a sort of sweet spot for RV, with a decent balance between brightness, rotational velocity, and spectral line availability. Also being cooler, Alf Cen B's HZ is closer in, making the planet more dynamically stable than an HZ planet around Alf Cen A.

But as posted up thread isn't the biggest impediment to close in planets the fact that they are close orbiting binary pair.
Title: Re: Pale Red Dot
Post by: as58 on 08/25/2016 07:16 am
The falsified (http://arxiv.org/abs/1510.05598) planet detection for Alf Cen B was a hot ~Earth-mass planet (http://www.nature.com/nature/journal/v491/n7423/full/nature11572.html), not a hot Jupiter.

Regarding A vs B, the B star is more RV-stable (K-type stars are a sort of sweet spot for RV, with a decent balance between brightness, rotational velocity, and spectral line availability. Also being cooler, Alf Cen B's HZ is closer in, making the planet more dynamically stable than an HZ planet around Alf Cen A.

But as posted up thread isn't the biggest impediment to close in planets the fact that they are close orbiting binary pair.

It's not that close a pair and sufficiently close-in orbits would be stable. Unsurprisingly there's been a fair bit of research on this and as far as I know, even some orbits in the HZ could be stable.
Title: Re: Pale Red Dot
Post by: hop on 08/25/2016 07:16 am
As they would be easier to observe I would imagine with the habitable zone being further out from the stars.
On the flip side, they are *much* brighter: Proxima is ~0.0015 solar luminosity, while Alpha Centauri A and B are ~1.5 and ~0.5, respectively.
Title: Re: Pale Red Dot
Post by: Bynaus on 08/25/2016 07:18 am
The average distance between the Alpha Centauri A & B pair is 11 AU. At that distance, radiation from the second star is ~1% of the radiation of the one the planet is orbiting. No big deal.

@StarOne: my cold bucket of water was not directed at the planets potential habitability, only at the notion that it might escape tidal lock by having a large satellite.
Title: Re: Pale Red Dot
Post by: Star One on 08/25/2016 08:14 am
As they would be easier to observe I would imagine with the habitable zone being further out from the stars.
On the flip side, they are *much* brighter: Proxima is ~0.0015 solar luminosity, while Alpha Centauri A and B are ~1.5 and ~0.5, respectively.

It's curious that B though similar in size to the Sun is much less luminous and cooler as well. Do we know if its makeup differs in someway from the Sun to explain this difference.
Title: Re: Pale Red Dot
Post by: as58 on 08/25/2016 09:12 am
As they would be easier to observe I would imagine with the habitable zone being further out from the stars.
On the flip side, they are *much* brighter: Proxima is ~0.0015 solar luminosity, while Alpha Centauri A and B are ~1.5 and ~0.5, respectively.

It's curious that B though similar in size to the Sun is much less luminous and cooler as well. Do we know if its makeup differs in someway from the Sun to explain this difference.

Stellar luminosity depends very strongly on the mass. For stars with masses of about a solar mass luminosity is roughly proportional to mass to the fourth, so even a small difference in mass makes a large difference in luminosity.

The composition (metallicity) of Alpha Centauri A/B is very similar to the Sun.
Title: Re: Pale Red Dot
Post by: Ben the Space Brit on 08/25/2016 09:20 am
The composition (metallicity) of Alpha Centauri A/B is very similar to the Sun.

I read a textbook (admittedly about 20 years ago) that said that Sol, A-Centauri-A and -B and quite a few of the dimmer A- through hotter K-class stars in our immediate neighbourhood may be from the same star-forming region.

This is not just due to composition but due to similar trajectories and orbital periods around the galactic centre

P.S.: I'm sort of grinding my teeth at the "can't do it" ignorance of the number of people on the popular news sites who seem to think that Voyager-1's cruise speed represents the fastest it is possible to go with contemporary technology.
Title: Re: Pale Red Dot
Post by: Bob Shaw on 08/25/2016 09:50 am
Poyekhali!
Title: Re: Pale Red Dot
Post by: Star One on 08/25/2016 10:10 am
The composition (metallicity) of Alpha Centauri A/B is very similar to the Sun.

I read a textbook (admittedly about 20 years ago) that said that Sol, A-Centauri-A and -B and quite a few of the dimmer A- through hotter K-class stars in our immediate neighbourhood may be from the same star-forming region.

This is not just due to composition but due to similar trajectories and orbital periods around the galactic centre

P.S.: I'm sort of grinding my teeth at the "can't do it" ignorance of the number of people on the popular news sites who seem to think that Voyager-1's cruise speed represents the fastest it is possible to go with contemporary technology.

Could Proxima Centauri have originated in the same stellar nursery?
Title: Re: Pale Red Dot
Post by: Ben the Space Brit on 08/25/2016 10:25 am
Could Proxima Centauri have originated in the same stellar nursery?

It's not totally impossible. However, red dwarves can be a lot older than G- and K-class main sequence stars (as old as 10 billion years or even older by some models). It's a question that, again, you would answer by looking at the detailed chemical composition of the star, as metalicity tends to be the 'fingerprint' of the primordial nebula where the star formed.

There is actually a huge debate about Proxima's origin. It's orbit around the A-B close pair is so wide, eccentric and inclined that the 'smart' money is on 'captured object' but there are viable models that have Proxima starting out closer to A-B and then being ejected by the gravitational influence of the larger stars and ending up in its current orbit.

FWIW, and purely in my opinion, the existence of Proxima-B weighs against the 'ejected from a closer orbit' theory.
Title: Re: Pale Red Dot
Post by: Star One on 08/25/2016 11:08 am
Could Proxima Centauri have originated in the same stellar nursery?

It's not totally impossible. However, red dwarves can be a lot older than G- and K-class main sequence stars (as old as 10 billion years or even older by some models). It's a question that, again, you would answer by looking at the detailed chemical composition of the star, as metalicity tends to be the 'fingerprint' of the primordial nebula where the star formed.

There is actually a huge debate about Proxima's origin. It's orbit around the A-B close pair is so wide, eccentric and inclined that the 'smart' money is on 'captured object' but there are viable models that have Proxima starting out closer to A-B and then being ejected by the gravitational influence of the larger stars and ending up in its current orbit.

FWIW, and purely in my opinion, the existence of Proxima-B weighs against the 'ejected from a closer orbit' theory.

I thought I saw some articles pegging its age at 4.9 billion years?
Title: Re: Pale Red Dot
Post by: jgoldader on 08/25/2016 12:14 pm
I note that Proxima is pretty small, even for red dwarves. It may be interesting to see just how much of a radiation hazard there is that close in to such a low-output object.

Proxima is an active, flaring M-dwarf.  The paper Mongo62 quoted above says 250x the X-ray flux we get from Sol here at Earth, and then drop in flares, maybe Carrington-level, once in a while.   If the planet is real, I have a hard time believing that it's a happy oasis of life.  A lifeless rock would be my bet, though a bet I'd be quite happy to lose.

I was really heartened by the possibility of direct imaging, though E-ELT and the needed equipment are a good long while away.  Fingers crossed, though.

Title: Re: Pale Red Dot
Post by: Star One on 08/25/2016 12:25 pm
I note that Proxima is pretty small, even for red dwarves. It may be interesting to see just how much of a radiation hazard there is that close in to such a low-output object.

Proxima is an active, flaring M-dwarf.  The paper Mongo62 quoted above says 250x the X-ray flux we get from Sol here at Earth, and then drop in flares, maybe Carrington-level, once in a while.   If the planet is real, I have a hard time believing that it's a happy oasis of life.  A lifeless rock would be my bet, though a bet I'd be quite happy to lose.

I was really heartened by the possibility of direct imaging, though E-ELT and the needed equipment are a good long while away.  Fingers crossed, though.

There's nothing precluding the evolution of radiation hardened microbes. Once it gets going life at least from Earth's experience at a simple level seems to evolve to the hand it's dealt.
Title: Re: Pale Red Dot
Post by: jgoldader on 08/25/2016 03:16 pm
There's nothing precluding the evolution of radiation hardened microbes. Once it gets going life at least from Earth's experience at a simple level seems to evolve to the hand it's dealt.

You're one of them "glass half full" folks, aren't ya?  ;)
Title: Re: Pale Red Dot
Post by: Johnnyhinbos on 08/25/2016 03:39 pm
If 'b' is tidal locked, as is the best guess, and IF the planet managed to hang on to an atmosphere, then the temps should be a good deal warmer then the -20 C guess and the far side of the planet should have more radiation protection. Perhaps a potential fro low light, low temp life...?
Title: Pale Red Dot
Post by: Star One on 08/25/2016 04:28 pm
There's nothing precluding the evolution of radiation hardened microbes. Once it gets going life at least from Earth's experience at a simple level seems to evolve to the hand it's dealt.

You're one of them "glass half full" folks, aren't ya?  ;)

https://en.m.wikipedia.org/wiki/Deinococcus_radiodurans

By the way I've seen a number of people calling this planet Per Ardua which must make Stephen Baxter happy.
Title: Re: Pale Red Dot
Post by: hop on 08/25/2016 05:17 pm
Could Proxima Centauri have originated in the same stellar nursery?
Probably, but this isn't totally certain The Habitability of Proxima Centauri b I: Evolutionary Scenarios (http://arxiv.org/abs/1608.06919) has an overview:

Quote
Additional inferences rely on the assumption that Proxima formed with the α Cen binary. The similarities in the proper motion and parallax between Proxima and α Cen immediately led to speculation as to whether the stars are "physically connected or members of the same drift" (Voute 1917), i.e. are they bound or members of a moving group? The intervening century has failed to resolve this central question. If Proxima is just a random star in the solar neighborhood, Matthews & Gilmore (1993) concluded that the probability that Proxima would appear so close to α Cen is about 1 in a million, suggesting it is very likely the stars are somehow associated with each other.
If they aren't actually related, a lot of things we think we "know" about Proxima could be wrong, because many properties that are difficult to measure in M dwarfs are inferred from the other stars.

Quote
I thought I saw some articles pegging its age at 4.9 billion years?
That's an estimate for the Alpha Centauri stars, but again, the error bars are quite large, and their relationship to Proxima isn't totally certain.  Proxima's rotation rate and activity level do support an age in that ballpark, independent of the Alpha Centauri stars.

From the paper linked above
Quote
Combining the different model predictions and including 1σ uncertainties, the age of α Cen A is likely to be between 3.4 and 5.9 Gyr, with a mean of 4.78 Gyr.

α Cen B has also been studied via asteroseismology, but as with A, the results have not been consistent. Lundkvist et al. (2014) find significant discrepancies between their "Asteroseismology Made Easy" age (1.5 Gyr) with other values, but with uncertainties in excess of 4 Gyr. The asteroseismic oscillations on B are much smaller than on A, which make analyses more diffcult (see, e.g. , Carrier & Bourban 2003), leading to the large uncertainty. Combining studies of A and B, we must conclude that the ages of the two stars are uncertain by at least 25%. Given the diffculty in measuring B's asteroseismic pulsations, we will rely on A's asteroseismic data and assume the age of A and B to be 4:8+1.1 -1.4 Gyr.

Title: Pale Red Dot
Post by: Star One on 08/25/2016 06:33 pm
Could Proxima Centauri have originated in the same stellar nursery?
Probably, but this isn't totally certain The Habitability of Proxima Centauri b I: Evolutionary Scenarios (http://arxiv.org/abs/1608.06919) has an overview:

Quote
Additional inferences rely on the assumption that Proxima formed with the α Cen binary. The similarities in the proper motion and parallax between Proxima and α Cen immediately led to speculation as to whether the stars are "physically connected or members of the same drift" (Voute 1917), i.e. are they bound or members of a moving group? The intervening century has failed to resolve this central question. If Proxima is just a random star in the solar neighborhood, Matthews & Gilmore (1993) concluded that the probability that Proxima would appear so close to α Cen is about 1 in a million, suggesting it is very likely the stars are somehow associated with each other.
If they aren't actually related, a lot of things we think we "know" about Proxima could be wrong, because many properties that are difficult to measure in M dwarfs are inferred from the other stars.

Quote
I thought I saw some articles pegging its age at 4.9 billion years?
That's an estimate for the Alpha Centauri stars, but again, the error bars are quite large, and their relationship to Proxima isn't totally certain.  Proxima's rotation rate and activity level do support an age in that ballpark, independent of the Alpha Centauri stars.

From the paper linked above
Quote
Combining the different model predictions and including 1σ uncertainties, the age of α Cen A is likely to be between 3.4 and 5.9 Gyr, with a mean of 4.78 Gyr.

α Cen B has also been studied via asteroseismology, but as with A, the results have not been consistent. Lundkvist et al. (2014) find significant discrepancies between their "Asteroseismology Made Easy" age (1.5 Gyr) with other values, but with uncertainties in excess of 4 Gyr. The asteroseismic oscillations on B are much smaller than on A, which make analyses more diffcult (see, e.g. , Carrier & Bourban 2003), leading to the large uncertainty. Combining studies of A and B, we must conclude that the ages of the two stars are uncertain by at least 25%. Given the diffculty in measuring B's asteroseismic pulsations, we will rely on A's asteroseismic data and assume the age of A and B to be 4:8+1.1 -1.4 Gyr.

Thanks for that.

I believe it's all the more important that we study Barnard's star for comparison not just because it's also nearby and another Red Dwarf, but at 10 billion years old it must be from at least one generation earlier in stellar population.

Quote
Dr. Anglada will discuss the new paper he is first author in reporting the presence of a 1.3 Earth mass exoplanet in a temperate orbit around Proxima Centauri. This finding was reported in Nature on Thursday 25 Aug 2016.
http://www.nature.com/nature/journal/v536/n7617/full/nature19106.html
Dr. Anglada will particpate remotely, and Dr. Franck Marchis of the SETI Institute will host a local panel (including Natalie Batalha and Thomas Barclay of NASA Ames) to discuss the implications of the finding. "Our little world will never seem the same again".
Read less
WHEN
Tuesday, August 30, 2016 from 12:00 PM to 1:30 PM (PDT)

https://www.eventbrite.com/e/a-terrestrial-exoplanet-at-proxima-centauri-tickets-26554200328?utm_content=buffer6257b&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

For those interested JWST appears to be discussing Proxima b on its Twitter feed at the moment.
Title: Re: Pale Red Dot
Post by: KelvinZero on 08/25/2016 11:05 pm
There's nothing precluding the evolution of radiation hardened microbes. Once it gets going life at least from Earth's experience at a simple level seems to evolve to the hand it's dealt.
IMO if it has oceans there is no problem for life finding a niche safe from x-rays. The question is more whether this environment would strip away volatiles?

Title: Re: Pale Red Dot
Post by: Mongo62 on 08/26/2016 12:24 am
Tutorial models of the climate and habitability of Proxima Centauri b: a thin atmosphere is sufficient to distribute heat given low stellar flux (http://arxiv.org/abs/1608.07263)

Proxima Centauri b, an Earth-size planet in the habitable zone of our nearest stellar neighbour, has just been discovered. A theoretical framework of synchronously rotating planets, in which the risk of a runaway greenhouse on the sunlight side and atmospheric collapse on the reverse side are mutually ameliorated via heat transport is discussed. This is developed via simple (tutorial) models of the climate. These show that lower incident stellar flux means that less heat transport, so less atmospheric mass, is required. The incident stellar flux at Proxima Centauri b is indeed low, which may help enhance habitability if it has suffered some atmospheric loss or began with a low volatile inventory.

Some interesting points made in this paper:

The spectrum of M-stars is shifted far to the red relative to the Sun, affecting climate and habitability. Snow and ice are near white around the Wein peak of sunlight, but dark at the Wein peak of M-star emission, so the ice-albedo feedback disappears (Joshi & Haberle 2012) (also, on a synchronous rotator, snow would fall on the unilluminated side). Little blue light is received, so Rayleigh scattering is of little importance for pressures of up to a few bar. Both of these effects bode well for weakly illuminated Proxima b: cooling mechanisms which endanger a planet near the outer edge of the habitable zone do not apply.

[...]

The triple point of water is 273 K; ice formation on the dark side is inevitable. With a very low water inventory, the risk of cold trapping all the water exists. With a medium-size inventory, glaciers would flow to the terminator, melt and evaporate. With a lot of water, there would be a global ocean like Earth’s, and water distribution would not be a problem.
Title: Re: Pale Red Dot
Post by: Star One on 08/26/2016 07:37 pm
The Plot Thickens: Habitable-Zone Exoplanets around Proxima Centauri and TRAPPIST-1

Quote
Introduction

As the time approaches to commission HPF on the Hobby-Eberly Telescope, we are learning that the spectrograph will be coming online in truly exciting times for exoplanet science!  The detection of habitable-zone exoplanets around two nearby M dwarf stars—including around the Sun’s nearest stellar neighbor—puts the science case for HPF into stark relief.  Let’s take a quick look at these systems, and discuss where HPF fits into the picture.

http://hpf.psu.edu/2016/08/25/the-plot-thickens/
Title: Re: Pale Red Dot
Post by: CuddlyRocket on 08/27/2016 03:01 am
Tutorial models of the climate and habitability of Proxima Centauri b: a thin atmosphere is sufficient to distribute heat given low stellar flux (http://arxiv.org/abs/1608.07263) ....

Some interesting points made in this paper: ....

I like the very last one:

Quote
The most wonderful thing about Proxima b is, of course, that we will likely be able to characterize his atmosphere—its presence or absence, its temperature and composition—in my lifetime, and thereby prove all our theories wrong.
Title: Re: Pale Red Dot
Post by: Star One on 08/27/2016 07:23 am
Tutorial models of the climate and habitability of Proxima Centauri b: a thin atmosphere is sufficient to distribute heat given low stellar flux (http://arxiv.org/abs/1608.07263) ....

Some interesting points made in this paper: ....

I like the very last one:

Quote
The most wonderful thing about Proxima b is, of course, that we will likely be able to characterize his atmosphere—its presence or absence, its temperature and composition—in my lifetime, and thereby prove all our theories wrong.
This business about never looking at M dwarfs for years because we assumed that they could never have planetary systems and then finding we were completely wrong, shows how dangerous it is to make assumptions in science.
Title: Re: Pale Red Dot
Post by: MP99 on 08/27/2016 07:58 am


Regardless I'm looking forward to future discoveries (and even sci-fi writings) about this world.

Try Proxima, by Stephen Baxter.

https://www.amazon.co.uk/dp/B00E0JYS8M/ref=dp-kindle-redirect?_encoding=UTF8&btkr=1

Cheers, Martin
Title: Re: Pale Red Dot
Post by: hop on 08/27/2016 09:01 pm
This business about never looking at M dwarfs for years because we assumed that they could never have planetary systems and then finding we were completely wrong, shows how dangerous it is to make assumptions in science.
IMO, that's a bit unfair. There have been plenty of "who ordered that" moments in exoplanet science: Hot Jupiters, super-earth/mini Neptunes, pulsar planets, circumbinary planets... but I'm not aware of anyone avoiding M dwarfs on the argument that they couldn't host planets at all.

Some surveys have avoided them for practical reasons: They are faint, noisy, and their potential for habitability is a lot less certain than sun-like stars, but despite all this people have been looking for (and finding) M dwarf planets for quite a long time. Remember the whole Pale Red Dot project started because older data was suggestive of a planet.

That said, the "and thereby prove all our theories wrong" comment is very well justified IMO. In the solar system and exoplanets, almost every significant advance in observational capability has turned up major surprises. Things like the back and forth arguments over whether M dwarfs can host habitable planets are useful to guide our thinking about the processes that affect them, but it's a safe bet the real systems will be weird in ways we never imagined.
Title: Re: Pale Red Dot
Post by: zubenelgenubi on 08/27/2016 09:49 pm
This business about never looking at M dwarfs for years because we assumed that they could never have planetary systems and then finding we were completely wrong, shows how dangerous it is to make assumptions in science.
IMO, that's a bit unfair. There have been plenty of "who ordered that" moments in exoplanet science: Hot Jupiters, super-earth/mini Neptunes, pulsar planets, circumbinary planets... but I'm not aware of anyone avoiding M dwarfs on the argument that they couldn't host planets at all.

Some surveys have avoided them for practical reasons: They are faint, noisy, and their potential for habitability is a lot less certain than sun-like stars, but despite all this people have been looking for (and finding) M dwarf planets for quite a long time. Remember the whole Pale Red Dot project started because older data was suggestive of a planet.

That said, the "and thereby prove all our theories wrong" comment is very well justified IMO. In the solar system and exoplanets, almost every significant advance in observational capability has turned up major surprises. Things like the back and forth arguments over whether M dwarfs can host habitable planets are useful to guide our thinking about the processes that affect them, but it's a safe bet the real systems will be weird in ways we never imagined.

Don't forget the ur-detection of exoplanets (subsequently disproved) via astrometry by Peter van de Kamp.

He first published about the detection of a planet orbiting M class red dwarf Barnard's Star in 1963.  He subsequently announced other exoplanet detections, by the same method, around other stars, including another M-dwarf, Lalande 21185.

During most of the 60's and early 70's, many astronomers considered red dwarfs THE most likely kind of star that the then-state-of-the-art could detect exoplanets orbiting.
Title: Pale Red Dot
Post by: Star One on 08/28/2016 10:10 pm
OPPORTUNITIES AND OBSTACLES FOR LIFE ON PROXIMA B

https://palereddot.org/opportunities-and-obstacles-for-life-on-proxima-b/

New article from the Pale Red Team.

If I am reading this right some of the statements in it seem to contradict other statements in this thread as regards Proxima's composition and where it formed.
Title: Re: Pale Red Dot
Post by: KelvinZero on 08/28/2016 11:15 pm
OPPORTUNITIES AND OBSTACLES FOR LIFE ON PROXIMA B

https://palereddot.org/opportunities-and-obstacles-for-life-on-proxima-b/

New article from the Pale Red Team.

If I am reading this right some of the statements in it seem to contradict other statements in this thread as regards Proxima's composition and where it formed.
Some interesting surprises for me in that article:
(1) Oxygen rich atmospheres can form on ocean worlds without photosynthesis from a process of stripping away hydrogen. (I knew oxygen could form, but in context I think he means rich in a laymans use of the word, not a scientists, who may get enthusiastic over a 0.5% or so.. )
(2) ..And also that an ocean world with an oxygen atmosphere may actually impede life beginning.
(3) A magnetic field can be maintained for billions of years without rotation, by convection.
Title: Re: Pale Red Dot
Post by: Mongo62 on 08/29/2016 01:33 am
Prospects for Characterizing the Atmosphere of Proxima Centauri b (http://arxiv.org/abs/1608.07345)

The newly detected Earth-mass planet in the habitable zone of Proxima Centauri could potentially host life - if it has an atmosphere that supports surface liquid water. We show that thermal phase curve observations with the James Webb Space Telescope (JWST) from 5-12 microns can be used to test the existence of such an atmosphere. We predict the thermal variation for a bare rock versus a planet with 35% heat redistribution to the nightside and show that a JWST phase curve measurement can distinguish between these cases at 5σ confidence. We also consider the case of an Earth-like atmosphere, and find that the ozone 9.8 micron band could be detected with longer integration times (a few months). We conclude that JWST observations have the potential to put the first constraints on the possibility of life around the nearest star to the Solar System.
Title: Re: Pale Red Dot
Post by: Robotbeat on 08/30/2016 05:36 pm
I can't wait until NASA Spaceflight dotcom has an Interstellar section! :)
Title: Re: Pale Red Dot
Post by: Star One on 08/30/2016 08:23 pm
Who else is looking for planets around Proxima Centauri.

http://www.universetoday.com/130345/else-looking-cool-worlds-around-proxima-centauri/
Title: Re: Pale Red Dot
Post by: Mongo62 on 08/31/2016 12:45 am
The Habitability of Proxima Centauri b: II: Environmental States and Observational Discriminants (http://arxiv.org/abs/1608.08620)

Proxima Centauri b provides an unprecedented opportunity to understand the evolution and nature of terrestrial planets orbiting M dwarfs. Although Proxima Cen b orbits within its star's habitable zone, multiple plausible evolutionary paths could have generated different environments that may or may not be habitable. Here we use 1D coupled climate-photochemical models to generate self-consistent atmospheres for evolutionary scenarios predicted in our companion paper (Barnes et al., 2016). These include high-O2, high-CO2, and more Earth-like atmospheres, with either oxidizing or reducing compositions. We show that these modeled environments can be habitable or uninhabitable at Proxima Cen b's position in the habitable zone. We use radiative transfer models to generate synthetic spectra and thermal phase curves for these simulated environments, and instrument models to explore our ability to discriminate between possible planetary states. These results are applicable not only to Proxima Cen b, but to other terrestrial planets orbiting M dwarfs. Thermal phase curves may provide the first constraint on the existence of an atmosphere, and JWST observations longward of 7 microns could characterize atmospheric heat transport and molecular composition. Detection of ocean glint is unlikely with JWST, but may be within the reach of larger aperture telescopes. Direct imaging spectra may detect O4, which is diagnostic of massive water loss and O2 retention, rather than a photosynthesis. Similarly, strong CO2 and CO bands at wavelengths shortward of 2.5 {\mu}m would indicate a CO2-dominated atmosphere. If the planet is habitable and volatile-rich, direct imaging will be the best means of detecting habitability. Earth-like planets with microbial biospheres may be identified by the presence of CH4 and either photosynthetically produced O2 or a hydrocarbon haze layer.
Title: Re: Pale Red Dot
Post by: kevin-rf on 08/31/2016 04:49 pm
I can't wait until NASA Spaceflight dotcom has an Interstellar section! :)

I can see it now, generations between posts.... It will be the great grand children replying to the last post ;)
Title: Re: Pale Red Dot
Post by: Star One on 08/31/2016 07:44 pm
A Closer Look at Proxima b

http://www.centauri-dreams.org/?p=36294
Title: Re: Pale Red Dot
Post by: Star One on 09/08/2016 07:20 pm
Just a reminder this Sunday's Sky At Night is all about Proxima b.

http://www.bbc.co.uk/programmes/b07vxfqp
Title: Re: Pale Red Dot
Post by: hop on 09/10/2016 05:47 am
SETI talk about Proxima b, with Dr Anglada from the discovery team and a panel of exoplanet astronomers

https://www.youtube.com/watch?v=_6eCF2FVcfo
Title: Re: Pale Red Dot
Post by: Star One on 09/12/2016 07:44 pm
Useful in consideration of planets around the other two Alpha Centauri stars.

On Planets in Binary Systems

http://www.centauri-dreams.org/?p=36365
Title: Re: Pale Red Dot
Post by: Mongo62 on 09/13/2016 01:06 am
This one is interesting, it considers what can be accomplished with the existing ESO VLT observatory with feasible upgrades to operational (SPHERE) and under-construction (EXPRESSO) instruments:

Atmospheric characterization of Proxima b by coupling the SPHERE high-contrast imager to the ESPRESSO spectrograph (http://arxiv.org/abs/1609.03082)

Context. The temperate Earth-mass planet Proxima b is the closest exoplanet to Earth and represents what may be our best ever opportunity to search for life outside the Solar System.

Aims. We aim at directly detecting Proxima b and characterizing its atmosphere by spatially resolving the planet and obtaining high-resolution reflected-light spectra.

Methods. We propose to develop a coupling interface between the SPHERE high-contrast imager and the new ESPRESSO spectrograph, both installed at ESO VLT. The angular separation of 37 mas between Proxima b and its host star requires the use of visible wavelengths to spatially resolve the planet on a 8.2-m telescope. At an estimated planet-to-star contrast of ~10^-7 in reflected light, Proxima b is extremely challenging to detect with SPHERE alone. The use of the high-contrast/high-resolution technique can overcome present limitations by combining a ~10^3-10^4 contrast enhancement from SPHERE to a ~10^4 gain from ESPRESSO.

Results. We find that significant but realistic upgrades to SPHERE and ESPRESSO would enable a 5-sigma detection of the planet and yield a measurement of its true mass and albedo in 20-40 nights of telescope time, assuming an Earth-like atmospheric composition. Moreover, it will be possible to probe the O2 bands at 627, 686 and 760 nm, the water vapour band at 717 nm, and the methane band at 715 nm. In particular, a 3.6-sigma detection of O2 could be made in about 60 nights of telescope time. Those would need to be spread over 3 years considering optimal observability conditions for the planet.

Conclusions. The very existence of Proxima b and the SPHERE-ESPRESSO synergy represent a unique opportunity to detect biosignatures on an exoplanet in the near future. It is also a crucial pathfinder experiment for the development of Extremely Large Telescopes and their instruments (abridged).

From the paper's conclusions:

– We find that the reflected spectrum from Proxima b can be detected at the 5-sigma level in 20-40 nights of telescope time for a contrast enhancement factor K = 3000 (SPHERE+) and a planet-to-star flux ratio of 1.0-1.4 x 10^7 (Earth-like atmospheres). This includes a measurement of the planet true mass (as opposed to minimum mass) and orbital inclination, and the measurement of its broadband albedo.

– We find that O2 can be detected at the 3.6-sigma level in about 60 nights of observing time at K = 5000, for a planet-to-star contrast of 1.4 x 10^7. Those nights would need to be spread over 3 years to guarantee optimal observability conditions of the planet and sucient separation between telluric and planetary O2 lines.

– We also show that H2O can be probed in a similar amount of telescope time provided the H2O column density is similar to wet regions of Earth.

– Finally, it is likely that CH4 is detectable as well if its column density is similar to or larger than the one seen in Jupiter and Saturn, although we could not address this point quantitatively.

In conclusion, while we do not underestimate the technical challenges of our proposed approach, we do believe that SPHERE+ESPRESSO is competitive for becoming the first instrument to characterize a habitable planet.
Title: Re: Pale Red Dot
Post by: Star One on 09/13/2016 06:17 am
Big question though is how much would this change cost.
Title: Re: Pale Red Dot
Post by: baldusi on 09/13/2016 11:52 am
Big question though is how much would this change cost.
Compared to any space project, probably pennies.
Title: Re: Pale Red Dot
Post by: hop on 09/13/2016 04:41 pm
Big question though is how much would this change cost.
Compared to any space project, probably pennies.
From the paper, it sounds like it should be significantly less than the cost of an instrument like SPHERE or ESPRESSO alone.

It does require a ton of telescope time for a potentially marginal detection, but OTOH as the authors note it's potentially usable (and less challenging) for more a number of other interesting planets too. It is also very positive for the ability of future 30m class ELTs to characterize Proxima b. Even if this technique is marginal with a 10m scope, essentially the same capabilities on a 30m scope should provide good signal in a reasonable amount of time.

It's interesting that in the SETI panel, Anglada was asked about ESPRESSO, and said it wouldn't really help get additional information about Proxima b, because the existing RV data is limited by stellar noise not the instrument (he was obviously only thinking in terms of RV.) The panelists all seemed pretty pessimistic about getting much before the ELTs come on line. However, Anglada did also say that he expected the existence of Proxima b to generate new, creative solutions.
Title: Re: Pale Red Dot
Post by: Star One on 09/13/2016 07:53 pm
Proxima b Is Surely Not “Earth-like.” But It’s A Research Magnet And Just May Be Habitable

http://www.manyworlds.space/index.php/2016/09/12/proxima-b-is-important-fascinating-and-maybe-habitable-but-surely-it-is-not-earth-like/
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 09/15/2016 07:22 pm
https://twitter.com/Pale_red_dot/status/776493236579885056
Quote
Something is happening! Exciting updates in short... #proximab #palereddot

 ???
Title: Re: Pale Red Dot
Post by: ugordan on 09/15/2016 07:29 pm
Huh... Could they also have detected it transiting?
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 09/15/2016 07:30 pm
That was my first thought, but I would be surprised tbh given the MOST teams's analysis of Proxima's variability.
Title: Re: Pale Red Dot
Post by: ugordan on 09/15/2016 07:35 pm
Yeah, not to mention the low transit probability. I *hate* teasers like that...
Title: Re: Pale Red Dot
Post by: Star One on 09/15/2016 07:47 pm
That was my first thought, but I would be surprised tbh given the MOST teams's analysis of Proxima's variability.

Well 1% still isn't 0 percent.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 09/15/2016 08:32 pm
A >1% transit probability is pretty large as transit probabilities go, but the MOST team's research showed that finding a transit will truly be needle-in-haystack stuff.

I don't want to get myself too excited about the posibility though, this announcement could be something more mundane .
Title: Re: Pale Red Dot
Post by: Bynaus on 09/15/2016 08:40 pm
Also, 1% is only the transit probability if we assume all orientations are equaly likely. They are, usually, but remember that a "transit-like event" has been seen at Alpha Cen B, and that the Alpha Cen A + B orbit is seen close to (although not perfectly) edge-on as seen from Earth, so perhaps the planetary orbital planes in the system are all roughly oriented along the Alpha Cen - Sun line. In that case, the probability of a transit of Proxima b might actually be somewhat higher...

I agree it sounds like a transit - what else could it be?
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 09/15/2016 08:46 pm
Indeed, i believe Guillem was alluding to that when he mentions the probability bounds for the true mass favoured the lower masses ~1.3-3 Me, which a very roughly edge-on disk would imply.
Title: Re: Pale Red Dot
Post by: hop on 09/15/2016 08:48 pm
That was my first thought, but I would be surprised tbh given the MOST teams's analysis of Proxima's variability.
Note that Kipping &co didn't rule out transits in the MOST data, they are are still searching and should have results Real Soon Now. Would be surprised if Pale Red Dot teased another teams results, although they would almost certainly know before hand since they shared their RV data with Kipping's team pre-publication.

Other thoughts:
Confirmation of the outer planet?

Could Gaia have resolved the question of whether Proxima is bound to Alpha Centauri? (would that be "exciting"?)
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 09/15/2016 09:28 pm
https://twitter.com/Pale_red_dot/status/776532446795927553

Quote
Does #proximab transit? #palereddot & co been working hard for months. No final answer, but a major facility is about to join the search...
Title: Re: Pale Red Dot
Post by: Bynaus on 09/15/2016 09:53 pm
I doubt that "major facility" would join the search without there being at least a solid hint in the MOST data.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 09/15/2016 09:58 pm
Depends what they mean by "major facility", but yes depending on what it is then it could be a big hint.

Edit: I could have walked to Proxima in the time it's taking to tell us what this major facility is...
Title: Re: Pale Red Dot
Post by: Bubbinski on 09/15/2016 10:39 pm
Would the major facility be ground based or space based?
Title: Re: Pale Red Dot
Post by: Star One on 09/15/2016 10:45 pm
Is that the major update then?
Title: Re: Pale Red Dot
Post by: as58 on 09/15/2016 10:58 pm
Would the major facility be ground based or space based?

I'm pretty sure that it would be ground based. VLT/CRIRES maybe?

Edit: Ok, not CRIRES because it's currently being upgraded.
Title: Re: Pale Red Dot
Post by: CuddlyRocket on 09/16/2016 03:18 am
That was my first thought, but I would be surprised tbh given the MOST teams's analysis of Proxima's variability.
Note that Kipping &co didn't rule out transits in the MOST data, they are are still searching and should have results Real Soon Now. Would be surprised if Pale Red Dot teased another teams results, although they would almost certainly know before hand since they shared their RV data with Kipping's team pre-publication.

The radial velocity data could help with establishing whether there's a transit; it could narrow down the time period within which the transit would occur (when the radial velocity switches from approaching to receding). It's harder to discern a transit among the variability when you have no idea when the transit occurs.

Of course, if Proxima b doesn't transit, but there's another planet that does, you're back to square one!

Quote
Other thoughts:
Confirmation of the outer planet?

Possible. The longer-period orbit means it would take longer to amass the data for confirmation. Apart from the fact that it takes longer for the same number of complete orbits, the outer planet may have less effect on the star (depending on its mass and orbital distance) relative to Proxima b.

Quote
Could Gaia have resolved the question of whether Proxima is bound to Alpha Centauri? (would that be "exciting"?)

Scientists often get excited about things that most people, even most other scientists, find distinctly ho-hum! Though to be fair, that's true for most people and their interests! :)

Personally, I have a bit of an interest in stellar designations etc, so I would certainly be interested in such a result. I'm hoping it isn't bound!

Gaia might be able to resolve the question; but you'd think the Gaia team would announce it. Then again, ESA is rubbish at PR!
Title: Re: Pale Red Dot
Post by: as58 on 09/16/2016 12:34 pm
Gaia might be able to resolve the question; but you'd think the Gaia team would announce it. Then again, ESA is rubbish at PR!

DR1 has no data on Proxima (there's a cut for high proper motions). Anyway, I'm not sure if even the final Gaia data will tell more about this. As far as I know the main uncertainty is the radial velocity of Proxima and I don't think Gaia will help much in that regard.

I know everyone likes to bash ESA PR, but I really think that the criticism gets sometimes a bit unreasonable...
Title: Re: Pale Red Dot
Post by: Star One on 09/16/2016 09:16 pm
What could the JWST tell us about Proxima b.

http://arstechnica.com/science/2016/09/if-proxima-centauri-b-has-an-atmosphere-james-webb-telescope-could-see-it/
Title: Re: Pale Red Dot
Post by: redliox on 09/16/2016 09:33 pm
What could the JWST tell us about Proxima b.

http://arstechnica.com/science/2016/09/if-proxima-centauri-b-has-an-atmosphere-james-webb-telescope-could-see-it/

The article mentions, to determine factors like albedo and orbit inclination in addition to numerous (even interesting) factors, about 100 hours of observation time is required from current telescopes, including the Webb.  The infrared-heavy vision of Webb may be helpful, especially if Proxima b is tidally locked.  The downside is that it wasn't designed with Proxima in mind (understandable, given when the project started nobody knew it existed), so the various JWST members are cautious about stating what Webb could do.  I'm sure, like the Hubble, it will contribute useful science as well.
Title: Re: Pale Red Dot
Post by: hop on 09/22/2016 09:14 pm
Via http://www.stsci.edu/ops/program-lists/HST-DD.html

"14860 - The most detailed high-energy picture of Proxima Centauri, our nearest extrasolar neighbor"

Quote
ABSTRACT
Proxima Centauri b is the nearest exoplanet to the Sun. It orbits an M5.5 dwarf and is potentially habitable. The latter statement, however, depends sensitively on the high-energy irradiation on the planet. Ribas et al. (2016) estimated the high-energy flux of the host star by collecting archival data from the X-ray to the FUV regime, but explicitly state that one "unavoidable complication of estimating XUV fluxes is [...] intrinsic [stellar] variability". Here, we propose to greatly improve upon this "unavoidable complication" by obtaining simultaneous X-ray and UV observations to measure a high-resolution irradiation spectrum and, thus, to assess the habitability of Proxima b.

Separately:
https://twitter.com/Hubble_Live/status/778066942389354498
Quote
I am looking at the star PROXIMA-CEN-SOURCE for Dr. Kailash C. Sahu using Wide Field Camera 3! http://bit.ly/2cP1yb7
This proposal is from the earlier campaign to observe microlensing events in 2015 http://archive.stsci.edu/proposal_search.php?mission=hst&id=13847
Title: Re: Pale Red Dot
Post by: Star One on 09/24/2016 09:37 pm
Are Stellar Storms Bad News for M-Dwarf Planets?

http://aasnova.org/2016/09/14/are-stellar-storms-bad-news-for-m-dwarf-planets/
Title: Re: Pale Red Dot
Post by: CuddlyRocket on 09/25/2016 09:38 pm
Are Stellar Storms Bad News for M-Dwarf Planets?

http://aasnova.org/2016/09/14/are-stellar-storms-bad-news-for-m-dwarf-planets/
Quote
With this many CME impacts even outside of the current-sheet plane, how can a planet hope to survive? The key lies in having a strong magnetic field to protect the planet. Such a field would deflect the charged particles from the CME, preventing the CME from stripping the planet’s atmosphere.

Kay and collaborators calculate that a habitable-zone mid-type M-dwarf exoplanet would need a planetary magnetic field between tens and hundreds of Gauss — 1 to 2 orders of magnitude more than that of Earth — to protect itself from these CMEs: difficult to muster, but not impossible!

There is the possibility of a habitable moon nestling inside the magnetic field of a gas giant it's orbiting, which will also give the protection of the planet's bulk for part of the moon's orbit. Though there is the question as to whether such an arrangement would be gravitationally stable, as well as the radiation environment around the gas giant itself, as per Jupiter's environs; although the moon can have still have its own magnetic field. Of course, we don't know of any exomoons yet (fame, if not fortune, awaits ...!).

It is looking more likely that very small stars won't be able to support actually habitable planets. As G2 dwarf stars obviously can, I wonder where the boundary lies: larger M dwarfs, K dwarfs or even smaller G dwarfs?
Title: Re: Pale Red Dot
Post by: redliox on 09/25/2016 10:06 pm
Are Stellar Storms Bad News for M-Dwarf Planets?

http://aasnova.org/2016/09/14/are-stellar-storms-bad-news-for-m-dwarf-planets/
Quote
With this many CME impacts even outside of the current-sheet plane, how can a planet hope to survive? The key lies in having a strong magnetic field to protect the planet. Such a field would deflect the charged particles from the CME, preventing the CME from stripping the planet’s atmosphere.

Kay and collaborators calculate that a habitable-zone mid-type M-dwarf exoplanet would need a planetary magnetic field between tens and hundreds of Gauss — 1 to 2 orders of magnitude more than that of Earth — to protect itself from these CMEs: difficult to muster, but not impossible!

There is the possibility of a habitable moon nestling inside the magnetic field of a gas giant it's orbiting, which will also give the protection of the planet's bulk for part of the moon's orbit. Though there is the question as to whether such an arrangement would be gravitationally stable, as well as the radiation environment around the gas giant itself, as per Jupiter's environs; although the moon can have still have its own magnetic field. Of course, we don't know of any exomoons yet (fame, if not fortune, awaits ...!).

It is looking more likely that very small stars won't be able to support actually habitable planets. As G2 dwarf stars obviously can, I wonder where the boundary lies: larger M dwarfs, K dwarfs or even smaller G dwarfs?

As far as Proxima Centauri (i.e. the primary object of discussion in this thread) goes, there aren't any gas giants within about 2 AU; past searches already eliminated anything larger than Earth orbiting relatively near the star.  Second, Jupiter funnels a lot of radiation into its moons' orbits so that shielding may be a two-edged sword depending on circumstances.  Third, while moons around gas giants allows for some stability...I think in the case of tide-locked M dwarf planets...moons in the habitable zone tend to be unlikely (then again observation may prove otherwise).

Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 09/29/2016 04:32 am
http://arxiv.org/abs/1609.08718
Quote
No Conclusive Evidence for Transits of Proxima b in MOST photometry

The analysis of Proxima Centauri's radial velocities recently led Anglada-Escudé et al. (2016) to claim the presence of a low mass planet orbiting the Sun's nearest star once every 11.2 days. Although the a-priori probability that Proxima b transits its parent star is just 1.5%, the potential impact of such a discovery would be considerable. Independent of recent radial velocity efforts, we observed Proxima Centauri for 12.5 days in 2014 and 31 days in 2015 with the MOST space telescope. We report here that we cannot make a compelling case that Proxima b transits in our precise photometric time series. Imposing an informative prior on the period and phase, we do detect a candidate signal with the expected depth. However, perturbing the phase prior across 100 evenly spaced intervals reveals one strong false-positive and one weaker instance. We estimate a false-positive rate of at least a few percent and a much higher false-negative rate of 20-40%, likely caused by the very high flare rate of Proxima Centauri. Comparing our candidate signal to HATSouth ground-based photometry reveals that the signal is somewhat, but not conclusively, disfavored (1-2 sigmas) leading us to argue that the signal is most likely spurious. We expect that infrared photometric follow-up could more conclusively test the existence of this candidate signal, owing to the suppression of flare activity and the impressive infrared brightness of the parent star.

Well that's disappointing.

Speaking of red/infrared followup and i've been looking at the observing schedules of probable 'major facilities' but drawn a blank on any scheduling, either now or planned, for photometry of Proxima. Not terribly surprising as proposing takes some time, but curious there's not even so much as a Directors Discretionary Time in sight either. HUGE amounts of followup being done right now on TRAPPIST-1 by many telescopes though!
Title: Re: Pale Red Dot
Post by: Star One on 09/29/2016 06:24 am
Could they hide any observing campaign that well and why would they hide it?
Title: Re: Pale Red Dot
Post by: hop on 09/29/2016 06:50 am
David Kipping (lead author of the MOST paper) has posted a video on the results

https://www.youtube.com/watch?v=fLPZiCZtr_k

Hints we might want to keep an eye on http://ssc.spitzer.caltech.edu/warmmission/scheduling/approvedprograms/ddt/ ;)
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 09/29/2016 07:58 am
Could they hide any observing campaign that well and why would they hide it?

Well often when a discovery is yet to be announced the project titles can be vague, or they could use more uncommon star designations as the target name. I did look for that too.

More likely either I just missed it, they've been told the time is approved but it's not yet on an observing schedule, or it's a facility that doesn't have a public observing schedule. MEarth South would be an obvious one as it is specifically designed for looking for transits at the red edge/infrared. Though tbh I'd be surprised if it wasn't on their target list since long before the discovery.
Title: Re: Pale Red Dot
Post by: as58 on 09/29/2016 08:24 am
I would think it's Spitzer as hop said above. It's been used quite a lot for detecting and characterising transits (indeed that has been one of the main uses of warm Spitzer). When I said that I'm pretty sure that the 'major facility' is ground-based, I completely forgot about Spitzer.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 09/29/2016 08:31 am
I looked at Spitzer, nothing yet, it is currently on a big programme sciencing the **** out of TRAPPIST-1.
Title: Re: Pale Red Dot
Post by: as58 on 09/29/2016 08:37 am
I looked at Spitzer, nothing yet, it is currently on a big programme sciencing the **** out of TRAPPIST-1.

If it's DDT as hinted, it could happen quickly outside the normal proposal cycle.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 09/29/2016 08:46 am
If it was a DDT it would still be on the schedule as Spitzer's are posted weekly. Even if not it would be on the observation log.

Besides I suspect they would need more time than a DDT could provide, they are going to want a significant out of transit to confirm any signal.

One that I would love to see happen but probably won't (because of a similar issue, legs are short) is using HIPO on SOFIA. Better for when you have confirmed it.
Title: Re: Pale Red Dot
Post by: as58 on 09/29/2016 09:31 am
Besides I suspect they would need more time than a DDT could provide, they are going to want a significant out of transit to confirm any signal. .

But confirming that it does not transit, which is the most likely case anyway, should be doable quickly, right? They know the phasing, so it wouldn't be necessary to keep staring for a long time.
Title: Re: Pale Red Dot
Post by: Star One on 10/07/2016 06:46 am
Planet in star system nearest our Sun 'may have oceans'

Quote
A rocky planet discovered in the "habitable" zone of the star nearest our Sun may be covered with oceans, researchers at France's CNRS research institute said Thursday.

http://phys.org/news/2016-10-planet-star-nearest-sun-oceans.amp
Title: Re: Pale Red Dot
Post by: zubenelgenubi on 10/07/2016 06:03 pm
Could they hide any observing campaign that well and why would they hide it?
Some further thoughts and observations?:
An increasing amount of ground-based observational astronomy is done remotely: the astronomers don't climb into the prime focus, or get to manipulate the telescope anymore (where's the fun in that?!--I know; there are some very good reasons for that.).

If one gets too Secret Squirrel with the observing plans, the staff who are actually executing the investigator's instructions might make a mistake.  Use the wrong instrument settings, or even observe the wrong star!

Becoming suddenly secretive may draw unwanted attention to one's observing sessions from your fellow astronomers.

I have known amateur astronomers who could deduce what you're observing by noting the general altitude/azimuth of the telescope tube's silhouette!
Title: Re: Pale Red Dot
Post by: redliox on 10/07/2016 06:11 pm
Planet in star system nearest our Sun 'may have oceans'

Quote
A rocky planet discovered in the "habitable" zone of the star nearest our Sun may be covered with oceans, researchers at France's CNRS research institute said Thursday.

http://phys.org/news/2016-10-planet-star-nearest-sun-oceans.amp

I heard about French scientists speculating the planet might be heavy with water via composition modeling.  A valid possibility, but still just speculation.  The planet could still be anything from a giant waterball to a Venusian twin to a supersized dry Mars.  I'm still just stunned at the odds of a planet being in the habitable zone of Proxima.
Title: Re: Pale Red Dot
Post by: Star One on 10/12/2016 06:52 pm
Optical, UV, and X-Ray Evidence for a 7-Year Stellar Cycle in Proxima Centauri

Quote
Stars of stellar type later than about M3.5 are believed to be fully convective and therefore unable to support magnetic dynamos like the one that produces the 11-year solar cycle. Because of their intrinsic faintness, very few late M stars have undergone long-term monitoring to test this prediction, which is critical to our understanding of magnetic field generation in such stars. Magnetic activity is also of interest as the driver of UV and X ray radiation, as well as energetic particles and stellar winds, that affect the atmospheres of close-in planets that lie within habitable zones, such as the recently discovered Proxima b. We report here on several years of optical, UV, and X-ray observations of Proxima Centauri (GJ 551; dM5.5e): 15 years of ASAS photometry in the V band (1085 nights) and 3 years in the I band (196 nights), 4 years of Swift XRT and UVOT observations (more than 120 exposures), and 9 sets of X-ray observations from other X-ray missions (ASCA, XMM-Newton, and three Chandra instruments) spanning 22 years. We confirm previous reports of an 83-day rotational period and find strong evidence for a 7-year stellar cycle, along with indications of differential rotation at about the solar level. X-ray/UV intensity is anti-correlated with optical V-band brightness for both rotational and cyclical variations. From comparison with other stars observed to have X-ray cycles we deduce a simple empirical relationship between X-ray cyclic modulation and Rossby number, and we also present Swift UV grism spectra covering 2300–600

http://m.mnras.oxfordjournals.org/content/early/2016/10/08/mnras.stw2570.abstract?keytype=ref&ijkey=rDKIzbzrnsgyvS4
Title: Re: Pale Red Dot
Post by: as58 on 10/25/2016 07:35 pm
A few hours of Proxima Centauri observations have appeared in Spitzer's schedule:
http://ssc.spitzer.caltech.edu/warmmission/scheduling/observinglogs/plan/week781.txt
Title: Re: Pale Red Dot
Post by: redliox on 10/26/2016 02:22 am
A few hours of Proxima Centauri observations have appeared in Spitzer's schedule:
http://ssc.spitzer.caltech.edu/warmmission/scheduling/observinglogs/plan/week781.txt

If I'm reading the info for Proxima's turn correctly, Spitzer is going to gaze at it for 533 minutes, just under 9 hours of time.  Hopefully that's enough to learn something about either the star or the planet(s) around it.
Title: Re: Pale Red Dot
Post by: Star One on 10/26/2016 05:57 pm
Are Planets Like Proxima b Water Worlds?

http://www.centauri-dreams.org/?p=36543
Title: Re: Pale Red Dot
Post by: Star One on 11/02/2016 07:49 pm
This new paper is appropriate to this thread.

The habitability of planets orbiting M-dwarf stars

Quote
Abstract
The prospects for the habitability of M-dwarf planets have long been debated, due to key differences between the unique stellar and planetary environments around these low-mass stars, as compared to hotter, more luminous Sun-like stars. Over the past decade, significant progress has been made by both space- and ground-based observatories to measure the likelihood of small planets to orbit in the habitable zones of M-dwarf stars. We now know that most M dwarfs are hosts to closely-packed planetary systems characterized by a paucity of Jupiter-mass planets and the presence of multiple rocky planets, with roughly a third of these rocky M-dwarf planets orbiting within the habitable zone, where they have the potential to support liquid water on their surfaces. Theoretical studies have also quantified the effect on climate and habitability of the interaction between the spectral energy distribution of M-dwarf stars and the atmospheres and surfaces of their planets. These and other recent results fill in knowledge gaps that existed at the time of the previous overview papers published nearly a decade ago by Tarter et al. (2007) and Scalo et al. (2007). In this review we provide a comprehensive picture of the current knowledge of M-dwarf planet occurrence and habitability based on work done in this area over the past decade, and summarize future directions planned in this quickly evolving field.

http://www.sciencedirect.com/science/article/pii/S0370157316303179
Title: Re: Pale Red Dot
Post by: Vultur on 11/03/2016 02:55 am
I'm still just stunned at the odds of a planet being in the habitable zone of Proxima.

Yeah. IMO, finding one that close suggests habitable zone worlds may be very common in general.
Title: Re: Pale Red Dot
Post by: Vultur on 11/03/2016 02:59 am
I note that Proxima is pretty small, even for red dwarves. It may be interesting to see just how much of a radiation hazard there is that close in to such a low-output object.

Proxima is an active, flaring M-dwarf.  The paper Mongo62 quoted above says 250x the X-ray flux we get from Sol here at Earth, and then drop in flares, maybe Carrington-level, once in a while.   If the planet is real, I have a hard time believing that it's a happy oasis of life.  A lifeless rock would be my bet, though a bet I'd be quite happy to lose.

I was really heartened by the possibility of direct imaging, though E-ELT and the needed equipment are a good long while away.  Fingers crossed, though.

The question, IMO, is what the solar flares would do to the atmosphere.

250x the X-ray flux -- or even far more -- shouldn't be a problem for the origin of life, since life originated in the oceans (on Earth anyway) and oceans are very good radiation shielding. It might cause problems for emergence of life onto land, but that doesn't sound beyond what hardy organisms could tolerate.
Title: Re: Pale Red Dot
Post by: redliox on 11/03/2016 02:33 pm
The question, IMO, is what the solar flares would do to the atmosphere.

250x the X-ray flux -- or even far more -- shouldn't be a problem for the origin of life, since life originated in the oceans (on Earth anyway) and oceans are very good radiation shielding. It might cause problems for emergence of life onto land, but that doesn't sound beyond what hardy organisms could tolerate.

Agreed; if anything's going to limit life around a red dwarf it'd be solar radiation.  There's probably some cut off point, in addition to any tidal locking concerns, between the K class and mid M class stars where you get TOO close to the star that kills life and possibly evaporate away the water and volatiles due to stellar activity. 

Planets themselves can exist anywhere matter can settle; that part of the Fermi Paradox seems firmly settled.  Now the next question to settle is how many of those planets, in either the traditional habitable zone or akin to Europa, are truly habitable.

I suppose now that Proxima is verified as planet-bearing, the next step is to image or otherwise study the habitable-zone planet and see if any more are around either Proxima or nearby AB.  Our neighboring star(s) are bough to attract significant attention in the coming decade nod oubt.
Title: Re: Pale Red Dot
Post by: baldusi on 11/03/2016 03:19 pm
Well, what would be the effect for a tidally locked ocean world? I would guess oceanic currents would handle heat flux in a very interesting way. Also, water clouds could seriously change the albedo.
Title: Re: Pale Red Dot
Post by: redliox on 11/03/2016 04:23 pm
Well, what would be the effect for a tidally locked ocean world? I would guess oceanic currents would handle heat flux in a very interesting way. Also, water clouds could seriously change the albedo.

Right; while "awkward" a tidal lock isn't as detrimental to habitability as previously thought.  Like I said, the greater showstopper would be if a star's uber-proximity would blow away the oceans and atmosphere.
Title: Re: Pale Red Dot
Post by: hop on 11/04/2016 06:29 am
This new paper is appropriate to this thread.

The habitability of planets orbiting M-dwarf stars

Available on arxiv https://arxiv.org/abs/1610.05765
Title: Re: Pale Red Dot
Post by: ugordan on 11/04/2016 12:51 pm
Well, what would be the effect for a tidally locked ocean world? I would guess oceanic currents would handle heat flux in a very interesting way. Also, water clouds could seriously change the albedo.

There's a paper posted on this earlier here. An ocean world is not of much use for heat transfer if the liquid is trapped under a layer of ice on the nightside.

Simulations show that it's actually all about atmospheric pressure and composition (abundance of CO2, etc). If the density is too low, you'll just end up with a cold trap on the dark side where the atmosphere will collapse onto. You need a minimum atmospheric density so the prevailing wind circulation manages to prevent this (superrotation like with Venus).
Title: Re: Pale Red Dot
Post by: zubenelgenubi on 11/04/2016 03:06 pm
re: habitability of worlds around M-class, flaring red dwarfs

I read a Larry Niven short story, "Flare Time," set on a moon in such a system.

Then I found out the short story was part of a 1985 collaborative short story collection, "Medea: Harlan's World."  Authors also include Harlan Ellison, Jack Williamson, Frederik Pohl, Hal Clement, Thomas M Disch, Frank Herbert, Poul Anderson, Kate Wilhelm, Theodore Sturgeon, and Robert Silverburg.

The short stories stem from a 1975 UCLA seminar "10 Tuesdays Down a Rabbit Hole."

https://en.wikipedia.org/wiki/Medea:_Harlan%27s_World

I don't know if the climatology they worked out back then is still valid today--I don't remember any fatal flaws.

Has anyone gotten Niven's thoughts/observations about this discovery?
Title: Re: Pale Red Dot
Post by: Star One on 11/08/2016 08:06 pm
FIRST LIGHT FOR BREAKTHROUGH LISTEN AT PARKES TELESCOPE, AUSTRALIA

Giant Radio Telescope Turns to New-Found Nearby Planet

Breakthrough Listen to Study Proxima b

San Francisco – November 7, 2016 – Breakthrough Listen, the 10-year, $100-million astronomical search for intelligent life beyond Earth launched in 2015 by Internet entrepreneur Yuri Milner and Stephen Hawking, today announced its first observations using the Parkes Radio Telescope in New South Wales, Australia.
Parkes joins the Green Bank Telescope (GBT) in West Virginia, USA, and the Automated Planet Finder (APF) at Lick Observatory in California, USA, in their ongoing surveys to determine whether civilizations elsewhere have developed technologies similar to our own. Parkes radio telescope is part of the Australia Telescope National Facility, owned and managed by Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO).
Drawing on over nine months of experience in operation of the dedicated Breakthrough Listen instrument at GBT, a team of scientists and engineers from the University of California, Berkeley's SETI Research Center (BSRC) deployed similar hardware at Parkes, bringing Breakthrough Listen’s unprecedented search tools to a wide range of sky inaccessible from the GBT. The Southern Hemisphere sky is rich with targets, including the center of our own Milky Way galaxy, large swaths of the galactic plane, and numerous other galaxies in the nearby Universe.
‘The Dish’ at Parkes played an iconic role in receiving the first deliberate transmissions from the surface of another world, as the astronauts of Apollo 11 set foot on our Moon. Now, Parkes joins once again in expanding human horizons as we search for the answer to one of our oldest questions: Are we alone?
“The Parkes Radio Telescope is a superb instrument, with a rich history,” said Pete Worden, Chairman of Breakthrough Prize Foundation and Executive Director of the Breakthrough Initiatives. “We’re very pleased to be collaborating with CSIRO to take Listen to the next level.”
With its new combined all-sky range, superb telescope sensitivity and computing capacity, Breakthrough Listen is the most powerful, comprehensive, and intensive scientific search ever undertaken for signs of intelligent life beyond Earth.
Moreover, this expansion of Breakthrough Listen’s range follows the announcement on October 12 that it will be joining forces with the new FAST telescope – the world’s largest filled-aperture radio receiver – to coordinate their searches for artificial signals. The two programs will exchange observing plans, search methods and data, including the rapid sharing of promising new signals for additional observation and analysis. The partnership represents a major step toward establishing a fully connected, global search for intelligent life in the Universe.
“The addition of Parkes is an important milestone,” said Yuri Milner, founder of the Breakthrough Initiatives, which include Breakthrough Listen. “These major instruments are the ears of planet Earth, and now they are listening for signs of other civilizations.”
First light focused on exo-Earth

After 14 days of commissioning and test observations, first light for Breakthrough Listen at Parkes was achieved on November 7, with an observation of the newly-discovered Earth-size planet orbiting the nearest star to the Sun. Proxima Centauri, a red dwarf star 4.3 light years from Earth, is now known to have a planet ("Proxima b") within its habitable zone – the region where water could exist in liquid form on the planet’s surface. Such “exo-Earths” (habitable zone exoplanets) are among the primary targets for Breakthrough Listen.
“The chances of any particular planet hosting intelligent life-forms are probably minuscule,” said Andrew Siemion, director of UC Berkeley SETI Research Center. “But once we knew there was a planet right next door, we had to ask the question, and it was a fitting first observation for Parkes. To find a civilization just 4.2 light years away would change everything.”
As the closest known exoplanet, Proxima b is also the current primary target for Breakthrough Listen's sister initiative, Breakthrough Starshot, which is developing the technology to send gram-scale spacecraft to the nearest stars.
“Parkes is one of the most highly cited radio telescopes in the world, with a long list of achievements to its credit, including the discovery of the first ‘fast radio burst’. Parkes’ unique view of the southern sky, and cutting-edge instrumentation, means we have a great opportunity to contribute to the search for extra-terrestrial life,” said Douglas Bock, Director of CSIRO Astronomy and Space Science.
Open data policy

As with the other Breakthrough Listen telescopes, data from Parkes will be freely available to the public online. Scientists, programmers, students, and others are invited to access the Breakthrough Listen archive for scientific research purposes, including helping perfect algorithms to sift through petabytes of raw data from the telescopes, screening for interfering signals from earth-bound technology. Volunteers can also help analyze data from Parkes by donating their spare computing power as part of BSRC’s legendary [email protected] project.
Scope of Parkes observations

Breakthrough Listen at Parkes will be the most comprehensive search of the southern sky for artificial signals in six key samples:
All 43 stars (at south declinations) within 5 parsecs, at 1-15 GHz*. Sensitive to the levels of radio transmission at which signals ‘leak’ from Earth-based radar transmitters (with available receivers).
1000 stars (south) of all spectral-types (OBAFGKM) within 50 parsecs (1-4 GHz).
One Million Nearby Stars (south). In 2016-2017, first 5,000 stars; 1 minute exposure (1-4 GHz).
Galactic plane and Center (1-4 GHz).
Centers of 100 nearby galaxies (south declinations): spirals, ellipticals, dwarfs, irregulars (1-4 GHz).
Exotic sources will include white dwarfs, neutron stars, black holes, and other anomalous natural sources (1-4 GHz).
Project Leadership

Pete Worden, Chairman, Breakthrough Prize Foundation
Lord Martin Rees, Astronomer Royal, Fellow of Trinity College; Emeritus Professor of Cosmology and Astrophysics, University of Cambridge
Andrew Siemion, Director, Berkeley SETI Research Center, University of California
Dan Werthimer, Co-founder and chief scientist of the [email protected] project; director of SERENDIP; principal investigator for CASPER, University of California
Matthew Bailes, Swinburne University
João Alves, University of Vienna
Jim Cordes, Cornell University
Paul Davies, Arizona State University
Frank Drake, UC Santa Cruz
Ron Ekers, CSIRO/ATNF
Andrew Fraknoi, Foothill College
Michael Garrett, University of Manchester
John Gertz, SETI Institute
Paul Horowitz, Harvard University
Andrew Howard, University of Hawaii
Nikolai Kardashev, Russian Academy of Sciences
Joseph Lazio, NASA JPL
Di Li, Chinese National Astronomical Observatory (CAS)
Chris Lintott, Oxford University
Avi Loeb, Harvard University
Shin-ya Narusawa, Nishi-Harima Astronomical Observatory (NHAO)
Brian Schmidt, Australian National University
Sara Seager, MIT
Seth Shostak, SETI Institute
Jill Tarter, SETI Institute
Lucianne Walkowicz, Adler Planetarium
Jason Wright, Penn State University
Shelley Wright, UC San Diego
For media inquiries: [email protected]
or
Rubenstein Communications, Inc.
New York, New York
Janet Wootten
[email protected] / +1.212.843.8024
Facebook: www.facebook.com/BreakthroughPrize/
Twitter: twitter.com/brkthroughprize
Youtube: www.youtube.com/user/breakthroughprize
Title: Re: Pale Red Dot
Post by: Star One on 11/12/2016 06:36 pm
Another planet around another nearby red dwarf.

Quote
And it seems the trend is likely to continue, with the latest discovery comes from a team of European scientists. Using data from the ESO’s High Accuracy Radial velocity Planet Searcher (HARPS) and HARPS-N instruments, they detected an exoplanet candidate orbiting around GJ 536 – an M-class red dwarf star located about 32.7 light years (10.03 parsecs) from Earth.

According to their study, “A super-Earth Orbiting the Nearby M-dwarf GJ 536“, this planet is a super-Earth – a class of exoplanet that has between more than one, but less than 15, times the mass of Earth. In this case, the planet boasts a minimum of 5.36 ± 0.69 Earth masses, has an orbital period of 8.7076 ± 0.0025 days, and orbits its sun at a distance of 0.06661 AU.

http://www.universetoday.com/131879/discovery-nearby-super-earth-5-times-mass/

Paper.

https://arxiv.org/pdf/1611.02122v1.pdf
Title: Re: Pale Red Dot
Post by: hop on 11/17/2016 03:53 am
Paper arguing the Proxima is indeed bound to A and B: https://arxiv.org/abs/1611.03495
Quote
Proxima and Alpha Centauri AB have almost identical distances and proper motions with respect to the Sun. Although the probability of such similar parameters is in principle very low, the question whether they actually form a single gravitationally bound triple system has been open since the discovery of Proxima one century ago. Owing to recent high precision radial velocity measurements and the revision of the parameters of the Alpha Cen pair, we show that Proxima and Alpha Cen are gravitationally bound with a high degree of confidence. The orbital period of Proxima is approximately 600 000 years, with a moderate excentricity of 0.42 +0.07 -0.08. Proxima comes within 5.3 -0.9 +1.2 kAU of Alpha Cen at periastron, and the apastron occurs at 12.9 +0.3 -0.1 kAU. This orbital motion may have influenced the formation or evolution of the recently discovered planet orbiting Proxima as well as circumbinary planet formation around Alpha Cen.

There's also a summary on astrobites https://astrobites.org/2016/11/16/settling-the-proxima-centauri-question/
Title: Re: Pale Red Dot
Post by: redliox on 11/17/2016 07:29 am
Paper arguing the Proxima is indeed bound to A and B: https://arxiv.org/abs/1611.03495

The paper says that Proxima should be the same age and material as AB.  In turn this implies their exoplanets would also be kin to each other.  This would make them an interesting study on extreme planetary formation.
Title: Re: Pale Red Dot
Post by: Star One on 02/08/2017 07:05 pm
NASA Finds Planets of Red Dwarf Stars May Face Oxygen Loss in Habitable Zones
The search for life beyond Earth starts in habitable zones, the regions around stars where conditions could potentially allow liquid water – which is essential for life as we know it – to pool on a planet’s surface. New NASA research suggests some of these zones might not actually be able to support life due to frequent stellar eruptions – which spew huge amounts of stellar material and radiation out into space – from young red dwarf stars.

Now, an interdisciplinary team of NASA scientists wants to expand how habitable zones are defined, taking into account the impact of stellar activity, which can threaten an exoplanet’s atmosphere with oxygen loss. This research was published in The Astrophysical Journal Letters on Feb. 6, 2017.

"If we want to find an exoplanet that can develop and sustain life, we must figure out which stars make the best parents,” said Vladimir Airapetian, lead author of the paper and a solar scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We’re coming closer to understanding what kind of parent stars we need.”

To determine a star’s habitable zone, scientists have traditionally considered how much heat and light the star emits. Stars more massive than our sun produce more heat and light, so the habitable zone must be farther out. Smaller, cooler stars yield close-in habitable zones.

But along with heat and visible light, stars emit X-ray and ultraviolet radiation, and produce stellar eruptions such as flares and coronal mass ejections – collectively called space weather. One possible effect of this radiation is atmospheric erosion, in which high-energy particles drag atmospheric molecules – such as hydrogen and oxygen, the two ingredients for water – out into space. Airapetian and his team's new model for habitable zones now takes this effect into account.


In this artist’s concept, X-ray and extreme ultraviolet light from a young red dwarf star cause ions to escape from an exoplanet’s atmosphere. Scientists have developed a model that estimates the oxygen ion escape rate on planets around red dwarfs, which plays an important role in determining an exoplanet’s habitability.
Credits: NASA Goddard/Conceptual Image Lab, Michael Lentz, animator/Genna Duberstein, producer
Download this video in HD formats from NASA Goddard's Scientific Visualization Studio
The search for habitable planets often hones in on red dwarfs, as these are the coolest, smallest and most numerous stars in the universe – and therefore relatively amenable to small planet detection.

"On the downside, red dwarfs are also prone to more frequent and powerful stellar eruptions than the sun," said William Danchi, a Goddard astronomer and co-author of the paper. "To assess the habitability of planets around these stars, we need to understand how these various effects balance out."

Another important habitability factor is a star's age, say the scientists, based on observations they've gathered from NASA’s Kepler mission. Every day, young stars produce superflares, powerful flares and eruptions at least 10 times more powerful than those observed on the sun. On their older, matured counterparts resembling our middle-aged sun today, such superflares are only observed once every 100 years.

“When we look at young red dwarfs in our galaxy, we see they’re much less luminous than our sun today,” Airapetian said. “By the classical definition, the habitable zone around red dwarfs must be 10 to 20 times closer-in than Earth is to the sun. Now we know these red dwarf stars generate a lot of X-ray and extreme ultraviolet emissions at the habitable zones of exoplanets through frequent flares and stellar storms.”

Superflares cause atmospheric erosion when high-energy X-ray and extreme ultraviolet emissions first break molecules into atoms and then ionize atmospheric gases. During ionization, radiation strikes the atoms and knocks off electrons. Electrons are much lighter than the newly formed ions, so they escape gravity’s pull far more readily and race out into space.

Opposites attract, so as more and more negatively charged electrons are generated, they create a powerful charge separation that lures positively charged ions out of the atmosphere in a process called ion escape.

“We know oxygen ion escape happens on Earth at a smaller scale since the sun exhibits only a fraction of the activity of younger stars,” said Alex Glocer, a Goddard astrophysicist and co-author of the paper. “To see how this effect scales when you get more high-energy input like you’d see from young stars, we developed a model.”

The model estimates the oxygen escape on planets around red dwarfs, assuming they don’t compensate with volcanic activity or comet bombardment. Various earlier atmospheric erosion models indicated hydrogen is most vulnerable to ion escape. As the lightest element, hydrogen easily escapes into space, presumably leaving behind an atmosphere rich with heavier elements such as oxygen and nitrogen.

But when the scientists accounted for superflares, their new model indicates the violent storms of young red dwarfs generate enough high-energy radiation to enable the escape of even oxygen and nitrogen – building blocks for life’s essential molecules.   

“The more X-ray and extreme ultraviolet energy there is, the more electrons are generated and the stronger the ion escape effect becomes,” Glocer said. “This effect is very sensitive to the amount of energy the star emits, which means it must play a strong role in determining what is and is not a habitable planet.”

Considering oxygen escape alone, the model estimates a young red dwarf could render a close-in exoplanet uninhabitable within a few tens to a hundred million years. The loss of both atmospheric hydrogen and oxygen would reduce and eliminate the planet’s water supply before life would have a chance to develop.

“The results of this work could have profound implications for the atmospheric chemistry of these worlds,” said Shawn Domagal-Goldman, a Goddard space scientist not involved with the study. “The team’s conclusions will impact our ongoing studies of missions that would search for signs of life in the chemical composition of those atmospheres.”

Modeling the oxygen loss rate is the first step in the team’s efforts to expand the classical definition of habitability into what they call space weather-affected habitable zones. When exoplanets orbit a mature star with a mild space weather environment, the classical definition is sufficient. When the host star exhibits X-ray and extreme ultraviolet levels greater than seven to 10 times the average emissions from our sun, then the new definition applies. The team’s future work will include modeling nitrogen escape, which may be comparable to oxygen escape since nitrogen is just slightly lighter than oxygen.

The new habitability model has implications for the recently discovered planet orbiting the red dwarf Proxima Centauri, our nearest stellar neighbor. Airapetian and his team applied their model to the roughly Earth-sized planet, dubbed Proxima b, which orbits Proxima Centauri 20 times closer than Earth is to the sun.

Considering the host star’s age and the planet’s proximity to its host star, the scientists expect that Proxima b is subjected to torrents of X-ray and extreme ultraviolet radiation from superflares occurring roughly every two hours. They estimate oxygen would escape Proxima b’s atmosphere in 10 million years. Additionally, intense magnetic activity and stellar wind – the continuous flow of charged particles from a star – exacerbate already harsh space weather conditions. The scientists concluded that it’s quite unlikely Proxima b is habitable.   

“We have pessimistic results for planets around young red dwarfs in this study, but we also have a better understanding of which stars have good prospects for habitability,” Airapetian said. “As we learn more about what we need from a host star, it seems more and more that our sun is just one of those perfect parent stars, to have supported life on Earth.”

Related:

Solar Storms May Have Been Key to Life on Earth
ESO Discovers Earth-Size Planet in Habitable Zone of Nearest Star
NASA's Swift Mission Observes Mega Flares from a Mini Star
In the Zone: How Scientists Search for Habitable Planets
Lina Tran
NASA's Goddard Space Flight Center, Greenbelt, Md.
Last Updated: Feb. 8, 2017
Editor: Rob Garner
Title: Re: Pale Red Dot
Post by: Vultur on 02/09/2017 02:31 am
Something I've been wondering about for a while, though - what does that intense radiation do to the planet's surface?

I've read that water ice gets dissociated on Europa's surface by radiation from Jupiter's radiation belt, making oxygen which forms an ultra-super-thin ~picobar O2 "atmosphere" which hardly deserves the name. But Europa's gravity is pretty limited - even less than our Moon's, not enough to really hold an atmosphere.

So I'm wondering if an Earth-size planet's surface might get altered by radiation, releasing enough gas to replenish some sort of atmosphere (maybe not a habitable one)? Or is the radiation involved not that intense? I guess breaking O2 out of SiO2 would be really hard...
Title: Re: Pale Red Dot
Post by: Star One on 02/13/2017 03:33 pm
Finding Proxima b: the 'planet hunters' searching for signs of alien life around nearby stars

http://www.wired.co.uk/article/the-pale-red-dot-proxima-centauri-could-be-home-to-extraterrestrial-life
Title: Pale Red Dot
Post by: Star One on 02/14/2017 07:28 pm
The cosmic shoreline: the evidence that escape determines which planets have atmospheres, and what this may mean for Proxima Centauri b

Kevin J. Zahnle, David C. Catling
(Submitted on 11 Feb 2017)
Quote
The planets of the Solar System divide neatly between those with atmospheres and those without when arranged by insolation (I) and escape velocity (vesc). The dividing line goes as I∝v4esc. Exoplanets with reported masses and radii are shown to crowd against the extrapolation of the Solar System trend, making a metaphorical cosmic shoreline that unites all the planets. The I∝v4esc relation may implicate thermal escape. We therefore address the general behavior of hydrodynamic thermal escape models ranging from Pluto to highly-irradiated Extrasolar Giant Planets (EGPs). Energy-limited escape is harder to test because copious XUV radiation is mostly a feature of young stars, and hence requires extrapolating to historic XUV fluences (Ixuv) using proxies and power laws. An energy-limited shoreline should scale as Ixuv∝v3escρ√, which differs distinctly from the apparent Ixuv∝v4esc relation. Energy-limited escape does provide good quantitative agreement to the highly irradiated EGPs. Diffusion-limited escape implies that no planet can lose more than 1% of its mass as H2. Impact erosion, to the extent that impact velocities vimp can be estimated for exoplanets, fits to a vimp≈4−5vesc shoreline. The proportionality constant is consistent with what the collision of comet Shoemaker-Levy 9 showed us we should expect of modest impacts in deep atmospheres. With respect to the shoreline, Proxima Centauri b is on the metaphorical beach. Known hazards include its rapid energetic accretion, high impact velocities, its early life on the wrong side of the runaway greenhouse, and Proxima Centauri's XUV radiation. In its favor is a vast phase space of unknown unknowns.

https://arxiv.org/abs/1702.03386
Title: Re: Pale Red Dot
Post by: sghill on 02/15/2017 01:56 pm
More about Ion Escape.

I read this as bad news for critters on Proxima B.

Likely it's a UV blasted rock....

http://iopscience.iop.org/article/10.3847/2041-8213/836/1/L3

Abstract
Atmospheres of exoplanets in the habitable zones around active young G-K-M stars are subject to extreme X-ray and EUV (XUV) fluxes from their host stars that can initiate atmospheric erosion. Atmospheric loss affects exoplanetary habitability in terms of surface water inventory, atmospheric pressure, the efficiency of greenhouse warming, and the dosage of the UV surface irradiation. Thermal escape models suggest that exoplanetary atmospheres around active K-M stars should undergo massive hydrogen escape, while heavier species including oxygen will accumulate forming an oxidizing atmosphere. Here, we show that non-thermal oxygen ion escape could be as important as thermal, hydrodynamic H escape in removing the constituents of water from exoplanetary atmospheres under supersolar XUV irradiation. Our models suggest that the atmospheres of a significant fraction of Earth-like exoplanets around M dwarfs and active K stars exposed to high XUV fluxes will incur a significant atmospheric loss rate of oxygen and nitrogen, which will make them uninhabitable within a few tens to hundreds of Myr, given a low replenishment rate from volcanism or cometary bombardment. Our non-thermal escape models have important implications for the habitability of the Proxima Centauri's terrestrial planet.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 03/20/2017 06:02 pm
This one is interesting, it considers what can be accomplished with the existing ESO VLT observatory with feasible upgrades to operational (SPHERE) and under-construction (EXPRESSO) instruments:

Atmospheric characterization of Proxima b by coupling the SPHERE high-contrast imager to the ESPRESSO spectrograph (http://arxiv.org/abs/1609.03082)

...
Big question though is how much would this change cost.

A bit more detail here.  Appears they have applied for funding, no idea whether they have secured it though.  Plan was to be ready for end of 2020.

https://obswww.unige.ch/people/christophe.lovis/SPHERE-ESPRESSO_Lovis.pdf
Title: Pale Red Dot
Post by: Star One on 04/28/2017 07:14 pm
The full spectral radiative properties of Proxima Centauri

Quote
The discovery of Proxima b, a terrestrial temperate planet, presents the opportunity of studying a potentially habitable world in optimal conditions. A key aspect to model its habitability is to understand the radiation environment of the planet in the full spectral domain. We characterize the X-rays to mid-IR radiative properties of Proxima with the goal of providing the top-of-atmosphere fluxes on the planet. We also aim at constraining the fundamental properties of the star. We employ observations from a large number of facilities and make use of different methodologies to piece together the full spectral energy distribution of Proxima. In the high-energy domain, we pay particular attention to the contribution by rotational modulation, activity cycle, and flares so that the data provided are representative of the overall radiation dose received by the atmosphere of the planet. We present the full spectrum of Proxima covering 0.7 to 30000 nm. The integration of the data shows that the top-of-atmosphere average XUV irradiance on Proxima b is 0.293 W m^-2, i.e., nearly 60 times higher than Earth, and that the total irradiance is 877+/-44 W m^-2, or 64+/-3% of the solar constant but with a significantly redder spectrum. We also provide laws for the XUV evolution of Proxima corresponding to two scenarios. Regarding the fundamental properties of Proxima, we find M=0.120+/-0.003 Msun, R=0.146+/-0.007 Rsun, Teff=2980+/-80 K, and L=0.00151+/-0.00008 Lsun. In addition, our analysis reveals a ~20% excess in the 3-30 micron flux of the star that is best interpreted as arising from warm dust in the system. The data provided here should be useful to further investigate the current atmospheric properties of Proxima b as well as its past history, with the overall aim of firmly establishing the habitability of the planet.

https://arxiv.org/abs/1704.08449

Does this indicate anything in particular as regards the habitability of Proxima b?
Title: Re: Pale Red Dot
Post by: Hungry4info3 on 04/28/2017 09:12 pm
From the paper

"If we assume synchronous rotation, our estimates indicate that Proxima b could have lost 0.47 Earth-oceans to 1.07 Earth-oceans between 10 Myr and 90 Myr, when it reached the inner edge of the habitable zone at 1.5 x Earth-insolation. Our new calculations therefore suggest that, during that time, Proxima b may have lost more water than previously estimated by Ribas (2016), by about a factor of 1.25 to 3. Assuming non-synchronous rotation, the amount of water lost could range from 0.9 Earth-oceans to 1.91 Earth-oceans between 10 Myr and 200 Myr, when it reached the habitable zone inner edge at 0.9 x Earth-insolation."

"In spite of the strong volatile loses, the planet could still have a significant amount of water reservoir when it entered the habitable zone deepening on the initial content. What could have occurred beyond this point is uncertain. If we assume that the water loss processes were still active upon entering the habitable zone, we find that Proxima b could have lost up to 15-20 Earth-oceans during its lifetime. However this needs to be considered an extreme upper limit because the volatile loss mechanics would probably be significantly less efficient under such conditions."
Title: Pale Red Dot
Post by: Star One on 05/16/2017 08:11 am
Proxima B: Our closest neighbouring exoplanet could host 'alien life' climate models suggest

Climate simulations have revealed Proxima B could have liquid water on its surface.

http://www.ibtimes.co.uk/proxima-b-our-closest-neighbouring-exoplanet-could-host-alien-life-climate-models-suggest-1621694

This should be noted.

Quote
"Our model is better able to take into account the variations in radiation received by the planet due to its orbit than previous models. We find that in the right conditions, Proxima B could have liquid water on its surface and could be habitable. Our model does suffer from limitations, notably we have simply assumed that the planet has an earth-like atmosphere", Nathan Mayne told IBTimes UK.

"It's interesting for us to see that when we change a given parameter (over a reasonable range), the simulated climate and temperatures do not change that much. Proxima B could benefit from a remarkably stable climate regime".

Here's the paper in question.

https://arxiv.org/pdf/1702.08463.pdf
Title: Re: Pale Red Dot
Post by: Star One on 07/16/2017 01:59 pm
Arecibo observatory joins Red Dots today for simultaneous observations of Barnard’s star

Quote
The National Science Foundation’s Arecibo Observatory and the Planetary Habitability Laboratory of the University of Puerto Rico at Arecibo joins forces with Red Dots today to learn a bit more about the nearest red-dwarfs and its possible planets. This collaboration will simultaneously observe in both the optical and radio spectrum Barnard’s Star, a popular star in the science fiction literature. Next week we will have a few more articles here on Red Dots on the history of this remarkable star (featuring a special guest article by Centauri Dream‘s author Paul Gilster). Those adept to science fiction literature may recall that Arecibo’s telescope is the mythical observatory where Dr. Ellie Harroway starts her Search for Extra Terrestrial Intelligence (or SETI) in Carl Sagan’s novel and film Contact, so the execution of these coordinated observations is a special event for us.

Observations on Barnard’s star will last for about 1.5 hours and they will be carried out at the so-called C-band, which corresponds to frequencies between 4 to 5 GHz. For comparison, kitchen microwave ovens work at frequencies of about 2.5 GHz. These will be complemented with spectra, and photometric monitoring with the follow-up facilities already being used in Red Dots including;  SNO, LCO, TJO, and CARMENES. Data might also be obtained with ESO’s HARPS, but the weather forecast at La Silla is not promising today.

https://reddots.space/arecibo-observatory-joins-red-dots-today-for-simultaneous-observations-of-barnards-star/
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 10/05/2017 01:46 pm
https://www.twitter.com/RedDotsSpace/status/915922545643278337

Quote
Data collection finished! Final articles and reports in the next few days. Stay tunned #proximab #barnards #ross154
Title: Pale Red Dot
Post by: Star One on 10/05/2017 04:40 pm
Further to the above is another tweet.

Quote
Pale Red Dot @Pale_red_dot
It's true! Do you want to learn about possible siblings to #proximab All data available soon. Get ready to join the discussions with @reddotsspace #reddots

https://mobile.twitter.com/Pale_red_dot/status/915925141808394243
Title: Re: Pale Red Dot
Post by: jebbo on 10/07/2017 07:52 am
The data is here:
https://reddots.space/photometry-log-4-end-of-campaign/

---Tony
Title: Re: Pale Red Dot
Post by: hop on 11/03/2017 01:10 am
Hints of a Kuiper belt analog and possibly other stuff around Proxima Centauri

ALMA Discovery of Dust Belts Around Proxima Centauri (https://arxiv.org/abs/1711.00578) Guillem Anglada et al accepted for publication in The Astrophysical Journal Letters

Quote
Proxima Centauri, the star closest to our Sun, is known to host at least one terrestrial planet candidate in a temperate orbit. Here we report the ALMA detection of the star at 1.3 mm wavelength and the discovery of a belt of dust orbiting around it at distances ranging between 1 and 4 au, approximately. Given the low luminosity of the Proxima Centauri star, we estimate a characteristic temperature of about 40 K for this dust, which might constitute the dust component of a small-scale analog to our solar system Kuiper belt. The estimated total mass, including dust and bodies up to 50 km in size, is of the order of 0.01 Earth masses, which is similar to that of the solar Kuiper belt. Our data also show a hint of warmer dust closer to the star. We also find signs of two additional features that might be associated with the Proxima Centauri system, which, however, still require further observations to be confirmed: an outer extremely cold (about 10 K) belt around the star at about 30 au, whose orbital plane is tilted about 45 degrees with respect to the plane of the sky; and additionally, we marginally detect a compact 1.3 mm emission source at a projected distance of about 1.2 arcsec from the star, whose nature is still unknown.
Title: Pale Red Dot
Post by: Star One on 11/03/2017 04:41 pm
eso1735 — Science Release
ALMA Discovers Cold Dust Around Nearest Star


Quote
The ALMA Observatory in Chile has detected dust around the closest star to the Solar System, Proxima Centauri. These new observations reveal the glow coming from cold dust in a region between one to four times as far from Proxima Centauri as the Earth is from the Sun. The data also hint at the presence of an even cooler outer dust belt and may indicate the presence of an elaborate planetary system. These structures are similar to the much larger belts in the Solar System and are also expected to be made from particles of rock and ice that failed to form planets.

Proxima Centauri is the closest star to the Sun. It is a faint red dwarf lying just four light-years away in the southern constellation of Centaurus (The Centaur). It is orbited by the Earth-sized temperate world Proxima b, discovered in 2016 and the closest planet to the Solar System. But there is more to this system than just a single planet. The new ALMA observations reveal emission from clouds of cold cosmic dust surrounding the star.

The lead author of the new study, Guillem Anglada [1], from the Instituto de Astrofísica de Andalucía (CSIC), Granada, Spain, explains the significance of this find: “The dust around Proxima is important because, following the discovery of the terrestrial planet Proxima b, it’s the first indication of the presence of an elaborate planetary system, and not just a single planet, around the star closest to our Sun.”

Dust belts are the remains of material that did not form into larger bodies such as planets. The particles of rock and ice in these belts vary in size from the tiniest dust grain, smaller than a millimetre across, up to asteroid-like bodies many kilometres in diameter [2].

Dust appears to lie in a belt that extends a few hundred million kilometres from Proxima Centauri and has a total mass of about one hundredth of the Earth’s mass. This belt is estimated to have a temperature of about –230 degrees Celsius, as cold as that of the Kuiper Belt in the outer Solar System.

There are also hints in the ALMA data of another belt of even colder dust about ten times further out. If confirmed, the nature of an outer belt is intriguing, given its very cold environment far from a star that is cooler and fainter than the Sun. Both belts are much further from Proxima Centauri than the planet Proxima b, which orbits at just four million kilometres from its parent star [3].

Guillem Anglada explains the implications of the discovery: “This result suggests that Proxima Centauri may have a multiple planet system with a rich history of interactions that resulted in the formation of a dust belt. Further study may also provide information that might point to the locations of as yet unidentified additional planets.”

Proxima Centauri's planetary system is also particularly interesting because there are plans — the Starshot project — for future direct exploration of the system with microprobes attached to laser-driven sails. A knowledge of the dust environment around the star is essential for planning such a mission.

https://www.eso.org/public/news/eso1735/

https://www.youtube.com/watch?v=TuHj2DRGoiA
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 11/03/2017 10:57 pm
Astronomy has a Q&A with Guillem Anglada-Escudé (the Proxima b guy, not the lead author) that also discusses progress with Red Dots.

What do belts around Proxima Centauri mean for exoplanet research? (http://www.astronomy.com/news/2017/11/proxima-rings)
Title: Re: Pale Red Dot
Post by: redliox on 11/04/2017 04:01 pm
I'm glad we're finally learning details about our nearest neighbor.  A few thoughts already occur to me...

1) The fact there are belts implies Proxima has been stable as a system for a few eons, as the ALMA stuff mentions.  Habitable is another story, but a possible step in that direction.

2) If the belts are akin to those around our Sol, we can begin to guestimate where planets may be from where they're cleared out.  In Promxia's case, it would seem to be between 30-4 AU and then within ~1AU.  Little b's presence already implies the later.  Scientists are already thinking this is the case with other stars with belts, namely Epsilon Eridani.

Title: Re: Pale Red Dot
Post by: Bynaus on 11/04/2017 04:22 pm
Note that there is also a hint of an inner, warmer dust belt at approximately 0.4 AU. So it could really be a quite complex system of three belt. Proxima b is closer to the star than the innermost belt, i.e. it could represent an innermost group of planets, with additional planets between the 0.4 and 1 AU, and even more between 4 and 30 AU. I am sure we will learn much more about this system in the coming years. This work is only a "first glance" with ALMA.
Title: Re: Pale Red Dot
Post by: Star One on 11/04/2017 06:09 pm
Note that there is also a hint of an inner, warmer dust belt at approximately 0.4 AU. So it could really be a quite complex system of three belt. Proxima b is closer to the star than the innermost belt, i.e. it could represent an innermost group of planets, with additional planets between the 0.4 and 1 AU, and even more between 4 and 30 AU. I am sure we will learn much more about this system in the coming years. This work is only a "first glance" with ALMA.

Could there be planet(s) shepherding each of the rings of material to stabilise them?
Title: Re: Pale Red Dot
Post by: Ben the Space Brit on 11/05/2017 08:57 am
That's certainly the case of the main asteroid belt in the Sol system so would a similar structure in the Proxima system would imply the existence of a large (maybe Neptune-class) object in a tight ~2AU orbit around Proxima?
Title: Re: Pale Red Dot
Post by: jebbo on 11/07/2017 04:51 pm
The full HARPS radial velocity dataset for Proxima Centauri has been released.

https://reddots.space/full-harps-2017-dataset-now-available/ (https://reddots.space/full-harps-2017-dataset-now-available/)

Sadly, I'm travelling or I'd post a periodogram and maybe a folded curve if there is an obvious 2nd period
Maybe this weekend ...

--- Tony
Title: Re: Pale Red Dot
Post by: Hungry4info3 on 11/08/2017 03:58 am
When I subtract the b planet, the periodogram I get looks about like this (and this is done in a programme I wrote myself, it has a lot of work to do, so I am hesitant to believe anything in it).

After the daily sampling alias, the next highest signal is at 161.9 days. Might be a ~5 ME planet? I would like to see how the photometry data comes in, because as it is, I don't believe one could reliably assert a second planet with just the RV data, though I would love to be shown wrong if indeed one can.

Image 1: Periodogram of HRPS_pre2016, UVEZ, and HARPS_Oct1 after the first planet is subtracted.
Image 2: RV fit for a planet at ~162 days.
Image 3: Graphical representation of my two-planet fit.
Title: Re: Pale Red Dot
Post by: redliox on 11/08/2017 04:13 am
Note that there is also a hint of an inner, warmer dust belt at approximately 0.4 AU. So it could really be a quite complex system of three belt. Proxima b is closer to the star than the innermost belt, i.e. it could represent an innermost group of planets, with additional planets between the 0.4 and 1 AU, and even more between 4 and 30 AU.
When I subtract the b planet, the periodogram I get looks about like this (and this is done in a programme I wrote myself, it has a lot of work to do, so I am hesitant to believe anything in it).

After the daily sampling alias, the next highest signal is at 161.9 days. Might be a ~5 ME planet? I would like to see how the photometry data comes in, because as it is, I don't believe one could reliably assert a second planet with just the RV data, though I would love to be shown wrong if indeed one can.

Image 1: Periodogram of HRPS_pre2016, UVEZ, and HARPS_Oct1 after the first planet is subtracted.
Image 2: RV fit for a planet at ~162 days.
Image 3: Graphical representation of my two-planet fit.

Looking at Hungry4's chart, it looks like the potential 2nd planet has an orbit around ~0.3 AU which lines up with the potential warm belt at 0.4 AU.  Hopefully things can be confirmed.
Title: Re: Pale Red Dot
Post by: jebbo on 11/08/2017 07:20 am
When I subtract the b planet, the periodogram I get looks about like this (and this is done in a programme I wrote myself, it has a lot of work to do, so I am hesitant to believe anything in it).

Thanks! I have similar homebrew stuff but I'm away so can't run it until the weekend.
If it's easy to do, a periodogram after subtracting "b" and one on the residuals might be useful.

Quote
After the daily sampling alias, the next highest signal is at 161.9 days. Might be a ~5 ME planet? I would like to see how the photometry data comes in, because as it is, I don't believe one could reliably assert a second planet with just the RV data, though I would love to be shown wrong if indeed one can.

Does the dataset include H-index / S-index? If so, it's worth checking for correlation at 161.9 with those.

--- Tony
Title: Re: Pale Red Dot
Post by: Hungry4info3 on 11/08/2017 10:38 am
Unless I missed something obvious, they only give date, RV and RV_err. I would have loved to have some data on stellar activity indicators though given the star is active. My periodogram of residuals for the two-planet fit is attached. The highest peak is ~785 days, which appears to be a sampling alias (folding the data by 785 days confines all the data points to four spaced out clumps). Dark grey and light grey lines are 0.1 and 1% FAP based on Scargle (1982) ... though I guess most people are now going with Horne (1986)?
Title: Re: Pale Red Dot
Post by: jebbo on 11/08/2017 10:45 am
Unless I missed something obvious, they only give date, RV and RV_err.

Ah, I've been spoilt by the Keck/HiRES RV release :-)

--- Tony
Title: Re: Pale Red Dot
Post by: Hungry4info3 on 11/08/2017 03:37 pm
Yeah and you can usually get spectral line FWHM and bisector width from the raw HARPS data as well from the ESO website but all their Proxima Centauri data is proprietary there.  :(
Title: Re: Pale Red Dot
Post by: Star One on 11/15/2017 05:14 pm
ESO press release

Closest Temperate World Orbiting Quiet Star Discovered
ESO’s HARPS instrument finds Earth-mass exoplanet around Ross 128

A temperate Earth-sized planet has been discovered only 11 light-years from the Solar System by a team using ESO’s unique planet-hunting HARPS instrument. The new world has the designation Ross 128 b and is now the second-closest temperate planet to be detected after Proxima b. It is also the closest planet to be discovered orbiting an inactive red dwarf star, which may increase the likelihood that this planet could potentially sustain life. Ross 128 b will be a prime target for ESO’s Extremely Large Telescope, which will be able to search for biomarkers in the planet's atmosphere.

A team working with ESO’s High Accuracy Radial velocity Planet Searcher (HARPS) at the La Silla Observatory in Chile has found that the red dwarf star Ross 128 is orbited by a low-mass exoplanet every 9.9 days. This Earth-sized world is expected to be temperate, with a surface temperature that may also be close to that of the Earth. Ross 128 is the “quietest” nearby star to host such a temperate exoplanet.

“This discovery is based on more than a decade of HARPS intensive monitoring together with state-of-the-art data reduction and analysis techniques. Only HARPS has demonstrated such a precision and it remains the best planet hunter of its kind, 15 years after it began operations,” explains Nicola Astudillo-Defru (Geneva Observatory – University of Geneva, Switzerland), who co-authored the discovery paper.

Red dwarfs are some of the coolest, faintest — and most common — stars in the Universe. This makes them very good targets in the search for exoplanets and so they are increasingly being studied. In fact, lead author Xavier Bonfils (Institut de Planétologie et d'Astrophysique de Grenoble – Université Grenoble-Alpes/CNRS, Grenoble, France), named their HARPS programme The shortcut to happiness, as it is easier to detect small cool siblings of Earth around these stars, than around stars more similar to the Sun [1].

Many red dwarf stars, including Proxima Centauri, are subject to flares that occasionally bathe their orbiting planets in deadly ultraviolet and X-ray radiation. However, it seems that Ross 128 is a much quieter star, and so its planets may be the closest known comfortable abode for possible life.

Although it is currently 11 light-years from Earth, Ross 128 is moving towards us and is expected to become our nearest stellar neighbour in just 79 000 years — a blink of the eye in cosmic terms. Ross 128 b will by then take the crown from Proxima b and become the closest exoplanet to Earth!

With the data from HARPS, the team found that Ross 128 b orbits 20 times closer than the Earth orbits the Sun. Despite this proximity, Ross 128 b receives only 1.38 times more irradiation than the Earth. As a result, Ross 128 b’s equilibrium temperature is estimated to lie between -60 and 20°C, thanks to the cool and faint nature of its small red dwarf host star, which has just over half the surface temperature of the Sun. While the scientists involved in this discovery consider Ross 128b to be a temperate planet, uncertainty remains as to whether the planet lies inside, outside, or on the cusp of the habitable zone, where liquid water may exist on a planet’s surface [2].

Astronomers are now detecting more and more temperate exoplanets, and the next stage will be to study their atmospheres, composition and chemistry in more detail. Vitally, the detection of biomarkers such as oxygen in the very closest exoplanet atmospheres will be a huge next step, which ESO’s Extremely Large Telescope (ELT) is in prime position to take [3].

“New facilities at ESO will first play a critical role in building the census of Earth-mass planets amenable to characterisation. In particular, NIRPS, the infrared arm of HARPS, will boost our efficiency in observing red dwarfs, which emit most of their radiation in the infrared. And then, the ELT will provide the opportunity to observe and characterise a large fraction of these planets,” concludes Xavier Bonfils.

https://www.eso.org/public/news/eso1736/?lang
Title: Re: Pale Red Dot
Post by: Star One on 11/15/2017 07:53 pm
Flying through the Ross 128 planetary system

https://www.youtube.com/watch?v=BJbrJLsFQnQ (https://www.youtube.com/watch?v=BJbrJLsFQnQ)
Title: Re: Pale Red Dot
Post by: CuddlyRocket on 11/16/2017 05:10 am
Closest Temperate World Orbiting Quiet Star Discovered

You can find the paper at A temperate exo-Earth around a quiet M dwarf at 3.4 parsecs (https://www.eso.org/public/archives/releases/sciencepapers/eso1736/eso1736a.pdf)

Quote
(from the abstract) Here we report on our radial velocity observations of Ross 128 (Proxima Virginis, GJ447, HIP 57548), an M4 dwarf just 3.4 parsec away from our Sun. This source hosts an exo-Earth with a projected mass m sin i = 1.35M⊕ and an orbital period of 9.9 days. Ross 128 b receives ∼1.38 times as much flux as Earth from the Sun and its equilibrium ranges in temperature between 269 K for an Earth-like albedo and 213 K for a Venus-like albedo. Recent studies place it close to the inner edge of the conventional habitable zone. An 80-day long light curve from K2 campaign C01 demonstrates that Ross 128 b does not transit. Together with the All Sky Automated Survey (ASAS) photometry and spectroscopic activity indices, the K2 photometry shows that Ross 128 rotates slowly and has weak magnetic activity. In a habitability context, this makes survival of its atmosphere against erosion more likely. Ross 128 b is the second closest known exo-Earth, after Proxima Centauri b (1.3 parsec), and the closest temperate planet known around a quiet star.

Interesting the use of the Kepler K2 data.
Title: Re: Pale Red Dot
Post by: jebbo on 11/16/2017 07:04 am
Interesting the use of the Kepler K2 data.

It's pretty standard to determine the stellar rotation period and activity from Kepler & K2 data.  That has been a nice side effect of the mission: we now have rotation data for a *lot* of stars.

BTW, determining the period for active stars is sometimes quite hard. Trappist-1 is an obvious example of this, where the K2 data clearly showed a different (slower) rotation rate than the published one.

--- Tony
Title: Re: Pale Red Dot
Post by: Mongo62 on 11/21/2017 01:43 am
Proxima B paper:

Searching for the Transit of the Earth--mass exoplanet Proxima~Centauri~b in Antarctica: Preliminary Result (https://arxiv.org/abs/1711.07018)

Proxima~Centauri is known as the closest star from the Sun. Recently, radial velocity observations revealed the existence of an Earth--mass planet around it. With an orbital period of ∼11 days, the surface of Proxima Centauri b is temperate and might be habitable. We took a photometric monitoring campaign to search for its transit, using the Bright Star Survey Telescope at the Zhongshan Station in Antarctica. A transit--like signal appearing on September 8th, 2016, is identified tentatively. Its midtime, TC=2,457,640.1990±0.0017~HJD, is consistent with the predicted ephemeris based on RV orbit in a 1σ confidence interval. Time--correlated noise is pronounced in the light curve of Proxima Centauri, affecting detection of transits. We develop a technique, in a Gaussian process framework, to gauge the statistical significance of potential transit detection. The tentative transit signal reported here, has a confidence level of 2.5σ. Further detection of its periodic signals is necessary to confirm the planetary transit of Proxima Centauri b. We plan to monitor Proxima Centauri in next Polar night at Dome A in Antarctica, taking the advantage of continuous darkness. Kipping reported two tentative transit--like signals of Proxima Centauri b, observed by the Microvariability and Oscillation of Stars space Telescope in 2014 and 2015, respectively. The midtransit time of our detection is 138 minutes later than that predicted by their transit ephemeris. If all the signals are real transits, the misalignment of the epochs plausibly suggests transit timing variations of Proxima Centauri b induced by an outer planet in this system.
Title: Re: Pale Red Dot
Post by: jebbo on 11/21/2017 08:09 am
Personally, I don't find that very compelling.  The purported transit is within the 1-sigma noise, doesn't match the two previous tentative transits without a whopping big TTV, and the ALMA result suggests the system has a non-transiting inclination ... so I'm expecting a null result from their next Antarctic observing run.

But interesting nonetheless, and I may be proved wrong :)

--- Tony
Title: Re: Pale Red Dot
Post by: Star One on 11/21/2017 08:18 am
Personally, I don't find that very compelling.  The purported transit is within the 1-sigma noise, doesn't match the two previous tentative transits without a whopping big TTV, and the ALMA result suggests the system has a non-transiting inclination ... so I'm expecting a null result from their next Antarctic observing run.

But interesting nonetheless, and I may be proved wrong :)

--- Tony

I’ve seen a few comments along the lines of those stating it doesn’t transit have jumped the gun somewhat on the basis of available data.
Title: Re: Pale Red Dot
Post by: Mongo62 on 12/14/2017 01:21 am
Speaking for myself, a single transit event is interesting, but I would want to see at least three transits to confirm the existence of a planet.

A Candidate Transit Event around Proxima Centauri (https://arxiv.org/abs/1712.04483)

We present a single candidate transit event around Proxima Centauri, found during a blind transit search using a robotic 30\,cm telescope at Las Campanas Observatory. The event lasted 1 hour, with an estimated depth of 5\,mmag, and is inconsistent with the transit window predicted for the recently discovered planet b. We modeled the lightcurve under the assumption that the event was caused by a transiting exoplanet, and our model predicts the planet has a radius R∼1R⊕. We encourage continued monitoring of Proxima to elucidate the origin of this event.
Title: Re: Pale Red Dot
Post by: matthewkantar on 12/14/2017 11:18 pm
Three transits could be a long wait if the planet is as far out as our ice and gas giants.

Matthew
Title: Re: Pale Red Dot
Post by: Star One on 02/26/2018 07:41 pm
Powerful Flare from Star Proxima Centauri Detected with ALMA

Quote
ALMA data reveal that a powerful stellar flare erupted from Proxima Centauri last March. This space weather may make that system rather inhospitable to life after all.

https://public.nrao.edu/news/2018-alma-flare-proxima/
Title: Re: Pale Red Dot
Post by: Star One on 02/27/2018 08:02 pm
Article discussing the possible implications of the above paper.

Proxima Flare May Force Rethinking of Dust Belts

Quote
News of a major stellar flare from Proxima Centauri is interesting because flares like these are problematic for habitability. Moreover, this one may tell us something about the nature of the planetary system around this star, making us rethink previous evidence for dust belts there.

But back to the habitability question. Can red dwarf stars sustain life in a habitable zone much closer to the primary than in our own Solar System, when they are subject to such violent outbursts? What we learn in a new paper from Meredith MacGregor and Alycia Weinberger (Carnegie Institution for Science) is that the flare at its peak on March 24, 2017 was 10 times brighter than the largest flares our G-class Sun produces at similar wavelengths (1.3 mm).

https://www.centauri-dreams.org/2018/02/27/proxima-flare-may-force-rethinking-of-dust-belts/
Title: Re: Pale Red Dot
Post by: hop on 04/09/2018 05:25 pm
The First Naked-Eye Superflare Detected from Proxima Centauri (https://arxiv.org/abs/1804.02001)

Quote
Proxima b is a terrestrial-mass planet in the habitable-zone of Proxima Centauri. Proxima Centauri's high stellar activity however casts doubt on the habitability of Proxima b: sufficiently bright and frequent flares and any associated proton events may destroy the planet's ozone layer, allowing lethal levels of UV flux to reach its surface. In March 2016, the Evryscope observed the first naked-eye-visible superflare detected from Proxima Centauri. Proxima increased in brightness by a factor of ~68 during the superflare and released a bolometric energy of 10^33.5 erg, ~10X larger than any previously-detected flare from Proxima. Over the last two years the Evryscope has recorded 23 other large Proxima flares ranging in bolometric energy from 10^30.6 erg to 10^32.4 erg; coupling those rates with the single superflare detection, we predict at least five superflares occur each year. Simultaneous high-resolution HARPS spectroscopy during the Evryscope superflare constrains the superflare's UV spectrum and any associated coronal mass ejections. We use these results and the Evryscope flare rates to model the photochemical effects of NOx atmospheric species generated by particle events from this extreme stellar activity, and show that the repeated flaring is sufficient to reduce the ozone of an Earth-like atmosphere by 90% within five years. We estimate complete depletion occurs within several hundred kyr. The UV light produced by the Evryscope superflare therefore reached the surface with ~100X the intensity required to kill simple UV-hardy microorganisms, suggesting that life would struggle to survive in the areas of Proxima b exposed to these flares.
Edit:
Submitted, not yet reviewed, and the "naked eye" is a stretch. Undeniably a big flare through.
Title: Re: Pale Red Dot
Post by: Star One on 05/02/2018 07:48 pm
TRAPPIST-1e Has a Large Iron Core

Quote
The TRAPPIST-1 system provides an exquisite laboratory for understanding exoplanetary atmospheres and interiors. Their mutual gravitational interactions leads to transit timing variations, from which Grimm et al. (2018) recently measured the planetary masses with precisions ranging from 5% to 12%. Using these masses and the <5% radius measurements on each planet, we apply the method described in Suissa et al. (2018) to infer the minimum and maximum CRF (core radius fraction) of each planet. Further, we modify the maximum limit to account for the fact that a light volatile envelope is excluded for planets b through f. Only planet e is found to have a significant probability of having a non-zero minimum CRF, with a 0.7% false-alarm probability it has no core. Our method further allows us to measure the CRF of planet e to be greater than (49 +/- 7)% but less than (72 +/- 2)%, which is compatible with that of the Earth. TRAPPIST-1e therefore possess a large iron core similar to the Earth, in addition to being Earth-sized and located in the temperature zone.

https://arxiv.org/abs/1804.10618
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 07/07/2018 09:53 pm
https://twitter.com/RedDotsSpace/status/1015712357392306176
Quote
Attention #reddoters! New observing campaign starting today at HARPS @ESO. Updates on science work and follow-up opportunities to follow!
Title: Re: Pale Red Dot
Post by: redliox on 07/08/2018 04:02 am
https://twitter.com/RedDotsSpace/status/1015712357392306176
Quote
Attention #reddoters! New observing campaign starting today at HARPS @ESO. Updates on science work and follow-up opportunities to follow!

As the founder of this particular thread, I'm especially excited at a new study of Proxima!  ;D
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 07/08/2018 11:36 am
Oh, maybe not including proxima this time;

https://twitter.com/RedDotsSpace/status/1015920018687750145
Quote
Starting today to september 30th. New 3 targets : GJ 887 #10 nearest star-system, GJ 1061 #20, GJ 54.1 #21. Contributed observations welcome! @AAVSO call with details to be issued in short.
Title: Re: Pale Red Dot
Post by: ExoExplorer on 07/08/2018 02:43 pm
Oh, maybe not including proxima this time;

https://twitter.com/RedDotsSpace/status/1015920018687750145
Quote
Starting today to september 30th. New 3 targets : GJ 887 #10 nearest star-system, GJ 1061 #20, GJ 54.1 #21. Contributed observations welcome! @AAVSO call with details to be issued in short.
That's sort of good news to me. If the signal of proxima c is ambiguous (unable to confirm as planet or false positive), they wouldn't turn away to other targets.
Title: Re: Pale Red Dot
Post by: Star One on 09/12/2018 06:57 pm
The Closest Exoplanet to Earth Could Be 'Highly Habitable'

Quote
Just a cosmic hop, skip and jump away, an Earth-size planet orbits the closest star to our sun, Proxima Centauri.

Ever since the discovery of the exoplanet — known as Proxima Centauri b— in 2016, people have wondered whether it could be capable of sustaining life.

Now, using computer models similar to those used to study climate change on Earth, researchers have found that, under a wide range of conditions, Proxima Centauri b can sustain enormous areas of liquid water on its surface, potentially raising its prospects for harboring living organisms. [9 Strange, Scientific Excuses for Why Humans Haven't Found Aliens Yet]

"The major message from our simulations is that there's a decent chance that the planet would be habitable," said Anthony Del Genio, a planetary scientist at the NASA Goddard Institute for Space Studies in New York City. Del Genio is also the lead author of a paper describing the new research, which was published Sept. 5 in the journal Astrobiology.

https://www.livescience.com/63546-proxima-b-nearest-exoplanet-habitable.html

Title: Re: Pale Red Dot
Post by: redliox on 09/12/2018 09:24 pm
Conversational piece. Hopefully data from either JWST or the upcoming large new observatories on Earth can conclude Proxima's living condition. I've heard speculations that go either way to Earthlike or dead.
Title: Re: Pale Red Dot
Post by: Star One on 09/13/2018 06:46 am
Conversational piece. Hopefully data from either JWST or the upcoming large new observatories on Earth can conclude Proxima's living condition. I've heard speculations that go either way to Earthlike or dead.

Do you think only AI driven searches of data even on these large telescopes are going to be the only way to turn up transit events because of the difficulty of the target?
Title: Re: Pale Red Dot
Post by: redliox on 09/13/2018 08:08 pm
Conversational piece. Hopefully data from either JWST or the upcoming large new observatories on Earth can conclude Proxima's living condition. I've heard speculations that go either way to Earthlike or dead.

Do you think only AI driven searches of data even on these large telescopes are going to be the only way to turn up transit events because of the difficulty of the target?

Not alone no, plus I'd hardly call it AI although it saves astronomers time just as an automated observatory might.
Title: Re: Pale Red Dot
Post by: jbenton on 09/15/2018 12:22 am
The Closest Exoplanet to Earth Could Be 'Highly Habitable'

...

https://www.livescience.com/63546-proxima-b-nearest-exoplanet-habitable.html

This is fascinating! another exerpt from the article:

Quote
But the new simulations were more comprehensive than prior ones; they also included a dynamic, circulating ocean, which was able to transfer heat from one side of the exoplanet to the other very effectively. In the researchers' findings, the movement of the atmosphere and ocean combined so that "even though the night side never sees any starlight, there's a band of liquid water that's sustained around the equatorial region," Del Genio told Live Science.

He likened this heat circulation to our own planet's seaside climates. The U.S. East Coast is balmier than it would be otherwise, he said, because the Gulf Stream carries warm water up from the tropics. In California, by contrast, ocean currents bring cold water down from the North, and the West Coast is colder than it otherwise would be, Del Genio added.

Myself a Californian who is much more comfortable in the warmer waters of Massachusetts I can attest to this fact.


This is all well and good, but what about the enormous stellar flares?
Title: Re: Pale Red Dot
Post by: Star One on 09/15/2018 11:16 am
The Closest Exoplanet to Earth Could Be 'Highly Habitable'

...

https://www.livescience.com/63546-proxima-b-nearest-exoplanet-habitable.html

This is fascinating! another exerpt from the article:

Quote
But the new simulations were more comprehensive than prior ones; they also included a dynamic, circulating ocean, which was able to transfer heat from one side of the exoplanet to the other very effectively. In the researchers' findings, the movement of the atmosphere and ocean combined so that "even though the night side never sees any starlight, there's a band of liquid water that's sustained around the equatorial region," Del Genio told Live Science.

He likened this heat circulation to our own planet's seaside climates. The U.S. East Coast is balmier than it would be otherwise, he said, because the Gulf Stream carries warm water up from the tropics. In California, by contrast, ocean currents bring cold water down from the North, and the West Coast is colder than it otherwise would be, Del Genio added.

Myself a Californian who is much more comfortable in the warmer waters of Massachusetts I can attest to this fact.


This is all well and good, but what about the enormous stellar flares?

I’d hope they’ve accounted for that otherwise these simulations would be worthless.
Title: Re: Pale Red Dot
Post by: jebbo on 09/15/2018 05:24 pm
This is all well and good, but what about the enormous stellar flares?

I’d hope they’ve accounted for that otherwise these simulations would be worthless.

It's not just the flares that are problematic. M-dwarfs are VERY active when descending the Hiyashi track to become main sequence stars, and this takes ~100 MY. During this time there is HUGE volatile loss (water etc), so whether any planet starts with an ocean is very dependent on the initial conditions  ... to be left with any water you have to start with a LOT and it is unclear if there is a good delivery mechanism for so much.

Hence, I'm pessimistic on the habitability of M-dwarf planets (not ruling it out, but I suspect it is a rare case). On Proxima b in particular, I'm dubious given it is rather active. The Trappist-1 planets feel like a better bet

However, all this is dependent on initial conditions once planets have formed and the star turns on. And I don't think we know enough go be certain ...

--- Tony
Title: Re: Pale Red Dot
Post by: Star One on 09/16/2018 08:53 am
This is all well and good, but what about the enormous stellar flares?

I’d hope they’ve accounted for that otherwise these simulations would be worthless.

It's not just the flares that are problematic. M-dwarfs are VERY active when descending the Hiyashi track to become main sequence stars, and this takes ~100 MY. During this time there is HUGE volatile loss (water etc), so whether any planet starts with an ocean is very dependent on the initial conditions  ... to be left with any water you have to start with a LOT and it is unclear if there is a good delivery mechanism for so much.

Hence, I'm pessimistic on the habitability of M-dwarf planets (not ruling it out, but I suspect it is a rare case). On Proxima b in particular, I'm dubious given it is rather active. The Trappist-1 planets feel like a better bet

However, all this is dependent on initial conditions once planets have formed and the star turns on. And I don't think we know enough go be certain ...

--- Tony

Isn’t there still a lot of uncertainties in M-Dwarf stellar evolution? Sure I’ve read an article in New Scientist last year along these lines when talking about TRAPPIST-1?
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 10/01/2018 01:57 pm
https://www.twitter.com/RedDotsSpace/status/1046758835413798912



Edit:Ooh, tweets are embedded now.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 11/13/2018 04:39 pm
https://twitter.com/RedDotsSpace/status/1062395736535564288

I may be totally off on this but I think this might have something to do with Barnard's Star.
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 11/14/2018 08:11 am
^^^ Seems probable now.

https://twitter.com/coreyspowell/status/1062380985474531331
https://twitter.com/coreyspowell/status/1062501218596085760

My info was that another team had Barnard's Star radial velocity data so I don't know whether they've decided to collaborate or whether the Red Dots announcement is pre-emptive of that.
Title: Re: Pale Red Dot
Post by: MATTBLAK on 11/14/2018 08:27 am
Barnard's Star for the win with one or more 'Super Earths'?!
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 11/14/2018 08:53 am
If I remember correctly there was talk about a possible “cold” super-earth signal previously, though parameters like orbital period and msini can change significantly with better signal to noise.
Title: Re: Pale Red Dot
Post by: jebbo on 11/14/2018 02:08 pm
https://twitter.com/RedDotsSpace/status/1062722115663790081?s=19 (https://twitter.com/RedDotsSpace/status/1062722115663790081)

BTW, in the HZ, I think. Edit: not. It's at the snow line
Title: Re: Pale Red Dot
Post by: jebbo on 11/14/2018 04:36 pm
Paper will be available from Nature at 6pm GMT
Title: Re: Pale Red Dot
Post by: Alpha_Centauri on 11/14/2018 05:02 pm
^^^ Fortunately ESO provide free versions.

https://www.eso.org/public/archives/releases/sciencepapers/eso1837/eso1837a.pdf

Quote
A super-Earth planet candidate orbiting at the snow-line of Barnard’s star

At a distance of 1.8 parsecs, Barnard’s star (Gl 699) is a red dwarf with the largest apparent motion of any known stellar object. It is the closest single star to the Sun, second only to the a Centauri triple stellar system. Barnard’s star is also among the least magnetically active red dwarfs known and has an estimated age older than our Solar System. Its properties have made it a prime target for planet searches employing techniques such as radial velocity, astrometry, and direct imaging, all with different sensitivity limits but ultimately leading to disproved or null results. Here we report that the combination of numerous measurements from high-precision radial velocity instruments reveals the presence of a low-amplitude but significant periodic signal at 233 days. Independent photometric and spectroscopic monitoring, as well as the analysis of instrumental systematic effects, show that this signal is best explained as arising from a planetary companion. The candidate planet around Barnard’s star is a cold super-Earth with a minimum mass of 3.2 Earth masses orbiting near its snow-line. The combination of all radial velocity datasets spanning 20 years additionally reveals a long-term modulation that could arise from a magnetic activity cycle or from a more distant planetary object. Because of its proximity to the Sun, the proposed planet has a maximum angular separation of 220 milliarcseconds from Barnard’s star, making it an excellent target for complementary direct imaging and astrometric observations.
Title: Re: Pale Red Dot
Post by: as58 on 04/13/2019 05:41 am
Apparently a new (candidate) planet, Proxima Centauri c, was announced at Breakthrough Discuss. Orbital period of ~1900 days and minimum mass of ~6 m_earth. More details at Scientific American: https://www.scientificamerican.com/article/a-second-planet-may-orbit-earths-nearest-neighboring-star/
Title: Re: Pale Red Dot
Post by: jebbo on 04/13/2019 06:02 am
A screenshot from the presentation.

https://twitter.com/LeeBillings/status/1116788239396851712

--- Tony
Title: Re: Pale Red Dot
Post by: Ben the Space Brit on 04/14/2019 05:50 pm
IIRC, way back it was thought that Barnard's Star had a companion that was brown dwarf mass. That was disproven in time but a super-Earth is a nice alternative.
Title: Re: Pale Red Dot
Post by: Star One on 04/16/2019 07:43 pm
Lessons from early Earth: UV surface radiation should not limit the habitability of active M star systems (https://academic.oup.com/mnras/article/485/4/5598/5426502)

Abstract
The closest potentially habitable worlds outside our Solar system orbit a different kind of star than our Sun: smaller red dwarf stars. Such stars can flare frequently, bombarding their planets with biologically damaging high-energy UV radiation, placing planetary atmospheres at risk of erosion and bringing the habitability of these worlds into question. However, the surface UV flux on these worlds is unknown. Here we show the first models of the surface UV environments of the four closest potentially habitable exoplanets: Proxima-b, TRAPPIST-1e, Ross-128b, and LHS-1140b assuming different atmospheric compositions, spanning Earth-analogue to eroded and anoxic atmospheres and compare them to levels for Earth throughout its geological evolution. Even for planet models with eroded and anoxic atmospheres, surface UV radiation remains below early Earth levels, even during flares. Given that the early Earth was inhabited, we show that UV radiation should not be a limiting factor for the habitability of planets orbiting M stars. Our closest neighbouring worlds remain intriguing targets for the search for life beyond our Solar system.