Author Topic: Pale Red Dot  (Read 75825 times)

Offline the_other_Doug

  • Senior Member
  • *****
  • Posts: 2726
  • Minneapolis, MN
  • Liked: 1785
  • Likes Given: 3387
Re: Pale Red Dot
« Reply #60 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.
-Doug  (With my shield, not yet upon it)

Offline Star One

  • Senior Member
  • *****
  • Posts: 9731
  • UK
  • Liked: 1863
  • Likes Given: 183
Re: Pale Red Dot
« Reply #61 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?

Offline Bynaus

  • Full Member
  • ****
  • Posts: 522
  • Dreamer, Scientist, Teacher, Writer, Husband & Dad
  • Switzerland
    • Final-Frontier.ch
  • Liked: 365
  • Likes Given: 252
Re: Pale Red Dot
« Reply #62 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... 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).
More of my thoughts: www.final-frontier.ch (in German)

Offline Star One

  • Senior Member
  • *****
  • Posts: 9731
  • UK
  • Liked: 1863
  • Likes Given: 183
Re: Pale Red Dot
« Reply #63 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... 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.

Offline Bynaus

  • Full Member
  • ****
  • Posts: 522
  • Dreamer, Scientist, Teacher, Writer, Husband & Dad
  • Switzerland
    • Final-Frontier.ch
  • Liked: 365
  • Likes Given: 252
Re: Pale Red Dot
« Reply #64 on: 08/16/2016 09:15 AM »
14% of solar radius / ~0.03 AU distance = ~5 times the diameter of the Sun on Earth.
More of my thoughts: www.final-frontier.ch (in German)

Offline Star One

  • Senior Member
  • *****
  • Posts: 9731
  • UK
  • Liked: 1863
  • Likes Given: 183
Re: Pale Red Dot
« Reply #65 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.

Offline jgoldader

  • Full Member
  • ****
  • Posts: 716
  • Liked: 265
  • Likes Given: 155
Re: Pale Red Dot
« Reply #66 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.
Recovering astronomer

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 28559
  • Minnesota
  • Liked: 8498
  • Likes Given: 5539
Re: Pale Red Dot
« Reply #67 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.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Star One

  • Senior Member
  • *****
  • Posts: 9731
  • UK
  • Liked: 1863
  • Likes Given: 183
Re: Pale Red Dot
« Reply #68 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?

Offline Alpha_Centauri

  • Full Member
  • ****
  • Posts: 629
  • England
  • Liked: 221
  • Likes Given: 133
Re: Pale Red Dot
« Reply #69 on: 08/16/2016 02:30 PM »
No, still far too large an inner working angle.

Offline jebbo

  • Full Member
  • ****
  • Posts: 641
  • Cambridge, UK
  • Liked: 267
  • Likes Given: 249
Re: Pale Red Dot
« Reply #70 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

Offline Star One

  • Senior Member
  • *****
  • Posts: 9731
  • UK
  • Liked: 1863
  • Likes Given: 183
Re: Pale Red Dot
« Reply #71 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.
« Last Edit: 08/16/2016 06:43 PM by Star One »

Offline as58

  • Full Member
  • ****
  • Posts: 811
  • Liked: 280
  • Likes Given: 181
Re: Pale Red Dot
« Reply #72 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.

Offline Phil Stooke

  • Full Member
  • ****
  • Posts: 483
  • Canada
  • Liked: 297
  • Likes Given: 0
Re: Pale Red Dot
« Reply #73 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


Offline Star One

  • Senior Member
  • *****
  • Posts: 9731
  • UK
  • Liked: 1863
  • Likes Given: 183
Re: Pale Red Dot
« Reply #74 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
Oh after that announcement last year about XX Trianguli I thought it was a major breakthrough.

Online CuddlyRocket

Re: Pale Red Dot
« Reply #75 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!

Offline as58

  • Full Member
  • ****
  • Posts: 811
  • Liked: 280
  • Likes Given: 181
Re: Pale Red Dot
« Reply #76 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
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

Offline jebbo

  • Full Member
  • ****
  • Posts: 641
  • Cambridge, UK
  • Liked: 267
  • Likes Given: 249
Re: Pale Red Dot
« Reply #77 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

Offline Alpha_Centauri

  • Full Member
  • ****
  • Posts: 629
  • England
  • Liked: 221
  • Likes Given: 133
Re: Pale Red Dot
« Reply #78 on: 08/17/2016 09:42 AM »
I would have thought they would wait til the Olympics has finished for maximum publicity.

Offline Bynaus

  • Full Member
  • ****
  • Posts: 522
  • Dreamer, Scientist, Teacher, Writer, Husband & Dad
  • Switzerland
    • Final-Frontier.ch
  • Liked: 365
  • Likes Given: 252
Re: Pale Red Dot
« Reply #79 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?
More of my thoughts: www.final-frontier.ch (in German)

Tags: