Author Topic: NASA's Trappist-1 Announcement - Feb 22, 2017  (Read 22335 times)

Offline Alpha_Centauri

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It could be a flare, but from my experience with Kepler data I would say most likely it is an artifact of the lightcurve processing correcting for the spacecraft pointing.
« Last Edit: 02/21/2017 07:04 PM by Alpha_Centauri »

Offline Star One

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A little more detail here.

Quote
It is possible that most of the planets confirmed thus circling far TRAPPIST-1 could be in the star's habitable zone. The inner 6 planets are probably rocky in composition and may be just the right temperature for liquid water to exist (between 0 - 100 degrees C) - if they have any water, that is. The outermost 7th planet still needs some more observations to nail down its orbit and composition.

http://spaceref.com/exoplanets/nearby-star-has-7-earth-sized-worlds---most-in-habitable-zone.html

By the way the Business Insider article now brings up a 404 error so someone must have told them they jumped the gun.
« Last Edit: 02/21/2017 09:18 PM by Star One »

Offline Ben the Space Brit

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I appreciate the excitement in scientific circles but, as I understand it, TRAPPIST-1 only barely classifies above a Brown Dwarf. That makes for very tight orbits to make for a thermal 'goldilocks zone'.

The problem I've always had with these dim red dwarf 'habitable zone' planets is that all the other physical characteristics are likely to make them sterile, most notably being tidally locked, really close to the photosphere (and thus likely to be bathed in lethal X- and UV-radiation levels) and probably without atmosphere due to lack of magnetic field )due to said tidal locking) and close proximity to the primary.

They make for useful studies and doubtless have their own unique charms (Pluto has taught us that there is no such thing as an 'uninteresting planetary body'). I guess I just have difficulty hyping these bodies up in my mind.

In my mind, with current sensing capabilities, the optimum habitable target world we're likely to find would be a hypothetical Galilean Moon-sized object orbiting a detected 'Warm Jupiter' in the habitable zone of a K- to A-class primary.
« Last Edit: 02/22/2017 10:51 AM by Ben the Space Brit »
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Offline Alpha_Centauri

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While I empathise the fact is the vast majority of stars are closer in scale to TRAPPIST-1 than to our own relatively large star. We need to understand just how habitable they may be. The fact is we have no real idea of how the conditions affect habitability. Remember, no one believed we would find much life at the bottom of the oceans , far from sunlight, until we went there and found hydrothermal vents. For all we know there could be exofish swimming happily a few meters beneath the surface on a waterworld here, easily protected from the X-Ray flux.

Anyway, b and f look interesting; they would appear possibly volatile-rich given the densities. b in particular could be steamy.
« Last Edit: 02/22/2017 12:34 PM by Alpha_Centauri »

Offline Star One

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I appreciate the excitement in scientific circles but, as I understand it, TRAPPIST-1 only barely classifies above a Brown Dwarf. That makes for very tight orbits to make for a thermal 'goldilocks zone'.

The problem I've always had with these dim red dwarf 'habitable zone' planets is that all the other physical characteristics are likely to make them sterile, most notably being tidally locked, really close to the photosphere (and thus likely to be bathed in lethal X- and UV-radiation levels) and probably without atmosphere due to lack of magnetic field )due to said tidal locking) and close proximity to the primary.

They make for useful studies and doubtless have their own unique charms (Pluto has taught us that there is no such thing as an 'uninteresting planetary body'). I guess I just have difficulty hyping these bodies up in my mind.

In my mind, with current sensing capabilities, the optimum habitable target world we're likely to find would be a hypothetical Galilean Moon-sized object orbiting a detected 'Warm Jupiter' in the habitable zone of a K- to A-class primary.

Actually TRAPPIST-1 one is a pretty quiet star as red dwarfs go so the issue of the planets being bathed in lethal radiation may be somewhat mitigated.

Anyway being as they are currently the only planets that we will be able to spectroscopical examine with current technology I am not sure such a downbeat response is warranted when nature provides such a fine exo solar system close at hand.
« Last Edit: 02/22/2017 12:58 PM by Star One »

Offline jebbo

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Anyway, b and f look interesting; they would appear possibly volatile-rich given the densities. b in particular could be steamy.

I doubt "b" ... given the resonances, I expect it's Io-like due to tidal heating. On the plus side, this means those nearer the ice line may be warmer than just flux would suggest, though I haven't run any numbers.

On planets around M dwarfs in general, like Ben, I'm sceptical due to both locking and desiccation when the stars are young.

--- Tony

Offline ugordan

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Given the apparent orbital resonances, is it at all plausible that some of those planets might not be tidally locked to the star, but instead ended up in a kind of resonant rotation similar to Mercury?

Offline Star One

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Anyway, b and f look interesting; they would appear possibly volatile-rich given the densities. b in particular could be steamy.

I doubt "b" ... given the resonances, I expect it's Io-like due to tidal heating. On the plus side, this means those nearer the ice line may be warmer than just flux would suggest, though I haven't run any numbers.

On planets around M dwarfs in general, like Ben, I'm sceptical due to both locking and desiccation when the stars are young.

--- Tony

Is that all we're going to do be downbeat about this, no wonder those in society who devalue science are having so much success these days.

Offline jebbo

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Is that all we're going to do be downbeat about this, no wonder those in society who devalue science are having so much success these days.

Why do you think this is downbeat? I'm sceptical over the habitability of planets around M dwarfs. That doesn't make them uninteresting or even mean there aren't plenty of habitable planets around other types of star.

It also doesn't mean I'm ruling it out, just that there are good reasons to doubt that just because a planet is in the HZ means it is at all close to being Earth-like or habitable.  Much depends on system formation, and most models don't allow enough volatiles for atmosphere / water to survive the initial flare activity.

--- Tony


Offline whitelancer64

I appreciate the excitement in scientific circles but, as I understand it, TRAPPIST-1 only barely classifies above a Brown Dwarf. That makes for very tight orbits to make for a thermal 'goldilocks zone'.

The problem I've always had with these dim red dwarf 'habitable zone' planets is that all the other physical characteristics are likely to make them sterile, most notably being tidally locked, really close to the photosphere (and thus likely to be bathed in lethal X- and UV-radiation levels) and probably without atmosphere due to lack of magnetic field )due to said tidal locking) and close proximity to the primary.

They make for useful studies and doubtless have their own unique charms (Pluto has taught us that there is no such thing as an 'uninteresting planetary body'). I guess I just have difficulty hyping these bodies up in my mind.

In my mind, with current sensing capabilities, the optimum habitable target world we're likely to find would be a hypothetical Galilean Moon-sized object orbiting a detected 'Warm Jupiter' in the habitable zone of a K- to A-class primary.

Just to correct a misconception: Venus has an extensive atmosphere and no magnetic field, so we know that magnetic fields are not a prerequisite for having or maintaining an atmosphere.

Venus and the Earth hold on to their atmospheres primarily by gravity - Nitrogen and Oxygen are too heavy to escape Earth's gravity, though we do lose lighter molecules like Hydrogen and Helium, primarily through solar heating of the exosphere which energizes those molecules to escape velocity, a process called Jeans Escape.

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

The exoplanets around TRAPPIST-1 are almost all very nearly the same mass or slightly more massive than the Earth, so we should expect they would be likely to have an atmosphere.
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Offline jebbo

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The exoplanets around TRAPPIST-1 are almost all very nearly the same mass or slightly more massive than the Earth, so we should expect they would be likely to have an atmosphere.

Sadly, that is too optimistic ... there have been a number of studies of both water and atmosphere loss from planets around late M dwarfs, and they give a pretty pessimistic outlook. The three most pertinent are:

On water loss: https://arxiv.org/abs/1605.00616
On atmosphere loss: https://arxiv.org/abs/1702.03386
On both: http://iopscience.iop.org/article/10.3847/2041-8213/836/1/L3

[ The final one is unfortunately behind a paywall ]

A lot depends on the initial conditions, on migration, and on later volatile delivery ... so not ruled out, but also not a given.  On the plus side, Trappist-1 is an almost perfect test bed for this!  All very exciting.

--- Tony


Offline Alpha_Centauri

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Anyway, b and f look interesting; they would appear possibly volatile-rich given the densities. b in particular could be steamy.

I doubt "b" ... given the resonances, I expect it's Io-like due to tidal heating. On the plus side, this means those nearer the ice line may be warmer than just flux would suggest, though I haven't run any numbers.

I don't know, an "Io" approximately the radius of Earth should be considerably more dense.

Anyway hopefully there'll be some constraints mentioned in the announcements.

Offline Blackstar

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Offline Star One

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Is that all we're going to do be downbeat about this, no wonder those in society who devalue science are having so much success these days.

Why do you think this is downbeat? I'm sceptical over the habitability of planets around M dwarfs. That doesn't make them uninteresting or even mean there aren't plenty of habitable planets around other types of star.

It also doesn't mean I'm ruling it out, just that there are good reasons to doubt that just because a planet is in the HZ means it is at all close to being Earth-like or habitable.  Much depends on system formation, and most models don't allow enough volatiles for atmosphere / water to survive the initial flare activity.

--- Tony

Fair enough.

Did I imagine it or did I read that they had spent 1500h observing this system using the HST.

Offline as58

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Did I imagine it or did I read that they had spent 1500h observing this system using the HST.

I missed the article when it was up, but there's no way they could've gotten anywhere close to that number of hours.

edit: I think 1500 hours refers to total time with all telescopes including Spitzer, on which they did get several hundred hours. A quick look at accepted proposals shows about 40 orbits of HST observations.
« Last Edit: 02/22/2017 03:55 PM by as58 »

Offline Star One

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Did I imagine it or did I read that they had spent 1500h observing this system using the HST.

I missed the article when it was up, but there's no way they could've gotten anywhere close to that number of hours.

edit: I think 1500 hours refers to total time with all telescopes including Spitzer, on which they did get several hundred hours. A quick look at accepted proposals shows about 40 orbits of HST observations.

Thanks for that clarification. That's why I asked as it was likely I had misremembered.

Offline jebbo

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edit: I think 1500 hours refers to total time with all telescopes including Spitzer, on which they did get several hundred hours. A quick look at accepted proposals shows about 40 orbits of HST observations.

The HST proposal at http://www.stsci.edu/hst/phase2-public/14873.pdf says:

Quote
Owing to over 1500 hours of monitoring including a recent 20-d long follow-up with the Spitzer Space Telescope, we have now constrained the architecture of TRAPPIST-1's system up to its ice line

My assumption is the 1500 includes the TRAPPIST observations ... and presumably AO / spectroscopic followup.

--- Tony

Offline Star One

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Here's the article from Nature.

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Other researchers are already using the Hubble Space Telescope to hunt for atmospheres on the TRAPPIST-1 planets. Kepler is also observing the system and will gather data that can better pin down the planetary masses, says Courtney Dressing, an astronomer at the California Institute of Technology in Pasadena. And the TRAPPIST team is building four new 1-metre-diameter telescopes in Chile to continue the work.

“For all the worlds that we see in science fiction, these are even more extraordinary,” says Hannah Wakeford, an exoplanet scientist at Goddard.

http://www.nature.com/news/these-seven-alien-worlds-could-help-explain-how-planets-form-1.21512

Quote
The Hubble Space Telescope characterized the atmospheres of TRAPPIST-1B and TRAPPIST-1C, finding that the two worlds probably aren't encircled by hydrogen and helium rich atmospheres, meaning their atmospheres could resemble our own.

Researchers will be able to get an even better look at these worlds in the future.

NASA's James Webb Space Telescope (JWST) — Hubble's telescope successor expected to launch in 2018 — should be able to peer deeply into the atmospheres of alien planets to try to see if they really could be like our own.

http://mashable.com/2017/02/22/seven-exoplanets-orbiting-trappist-1-star/
« Last Edit: 02/22/2017 05:16 PM by Star One »

Offline Alpha_Centauri

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Offline Blackstar

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