Author Topic: NASA's Trappist-1 Announcement - Feb 22, 2017  (Read 55360 times)

Offline Star One

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Offline Star One

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I've read in a few articles now that the fifth planet is considered the most habitable, why is this?
« Last Edit: 02/22/2017 06:53 pm by Star One »

Offline nacnud

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I think we've just found where firefly was set.

Offline nacnud

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I've read in a few articles now that the fifth planet is considered the most habitable, why is this?

From JPL

Quote
The TRAPPIST-1 system contains a total of seven planets, all around the size of Earth. Three of them -- TRAPPIST-1e, f and g -- dwell in their star's so-called "habitable zone."ť The habitable zone, or Goldilocks zone, is a band around every star (shown here in green) where astronomers have calculated that temperatures are just right -- not too hot, not too cold -- for liquid water to pool on the surface of an Earth-like world.

While TRAPPIST-1b, c and d are too close to be in the system's likely habitable zone, and TRAPPIST-1h is too far away, the planets' discoverers say more optimistic scenarios could allow any or all of the planets to harbor liquid water. In particular, the strikingly small orbits of these worlds make it likely that most, if not all of them, perpetually show the same face to their star, the way our moon always shows the same face to the Earth. This would result in an extreme range of temperatures from the day to night sides, allowing for situations not factored into the traditional habitable zone definition. The illustrations shown for the various planets depict a range of possible scenarios of what they could look like.
« Last Edit: 02/22/2017 07:08 pm by nacnud »

Offline as58

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Those brown, green, and blue zones in that TRAPPIST-1 system image seem to be IMO oddly placed. If we're looking just at irradiation and comparing to the Solar System, d should be easily inside the green zone, g well outside in the blue and f just about on the edge of green and blue. Or is there some more detail going into defining those zones (e.g. different stellar spectrum)?.
« Last Edit: 02/22/2017 07:29 pm by as58 »

Offline Star One

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Those brown, green, and blue zones in that TRAPPIST-1 system image seem to be IMO oddly placed. If we're looking just at irradiation and comparing to the Solar System, d should be easily inside the green zone, g well outside in the blue and f just about on the edge of green and blue. Or is there some more detail going into defining those zones (e.g. different stellar spectrum)?.

Everything I've read says that defining the habitable zone around an ultra cool dwarf is a tricky business so maybe it's related to that.

Offline Bynaus

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Yes, I think the runaway greenhouse limit for the smallest red dwarfs is around 0.9 S_Earth. So if scaled properly, the HZ is slightly further out for a smaller star. The paper preprint linked above says that they did climate models on all of them, and b, c, d ran into the runaway greenhouse state, while e, f, g remained temperate (h is likely too cold).

EDIT: if we are looking for a name for the system, I think we should call it ... ;)
« Last Edit: 02/22/2017 07:50 pm by Bynaus »
More of my thoughts: www.final-frontier.ch (in German)

Offline jebbo

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Tidal heating may also be significant for the inner planets (and I like that they illustrate "b" with something rather Io-like).  Enough so that I know they got radio observing time (don't know the instrument) looking for exo-aurorae but sadly there was a galaxy in the FoV

On atmospheres, probably worth looking at where they lie on the "cosmic shoreline".
[ https://arxiv.org/abs/1702.03386 ]

Edit: the masses of all but "f" are poorly constrained as only from TTVs. So K2 c12 light curve will hopefully constrain them better.  Then we should have a better idea of the bulk properties.

--- Tony
« Last Edit: 02/22/2017 07:50 pm by jebbo »

Offline Star One

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From the NASA press release I love the travel poster for this system.

https://exoplanets.nasa.gov/system/resources/detail_files/2159_posternormalsize.jpg

I see Kepler is currently studying the system looking for more planets plus further defining these discovered planets. Also Spitzer is carrying out another observing campaign. It also sounds like this will be part of JWST's initial target list.
« Last Edit: 02/22/2017 07:51 pm by Star One »

Offline baldusi

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Yes, I think the runaway greenhouse limit for the smallest red dwarfs is around 0.9 S_Earth. So if scaled properly, the HZ is slightly further out for a smaller star. The paper preprint linked above says that they did climate models on all of them, and b, c, d ran into the runaway greenhouse state, while e, f, g remained temperate (h is likely too cold).

EDIT: if we are looking for a name for the system, I think we should call it ... ;)

In the press conference they stated that the spectrum of the star was significantly in the IR range, so the energy/spectrum distribution is quite different. And that's where the atmospheric effects, absorption lines etc would come into play.

Offline Star One

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Quote
Andrew LePage February 22, 2017 at 15:02
> In particular, let’s see what Andrew LePage comes up with in his own Habitable Zone Reality Check.

Well, I’ve got a lot of data to digest before a write a “Habitable Planet Reality Check” (hopefully to come out in the next few days), but at first blush there does indeed seem to be reason to believe that at least one of these worlds is “potentially habitable”… maybe more. And the fact that TRAPPIST-1e has a fairly well determined radius and mass with a resulting density suggestive of a volatile-rich planet means that Earth-size planets orbiting small red dwarfs *CAN* hold onto their water and atmospheres despite flare activity, excessive X-ray/XUV flux, etc.. That’s a hopeful sign about the potential habitability of exoplanets like Proxima Centauri b or even Kepler 186f, among many others.

From here.

http://www.centauri-dreams.org/?p=37199

Offline Lars-J

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Those brown, green, and blue zones in that TRAPPIST-1 system image seem to be IMO oddly placed. If we're looking just at irradiation and comparing to the Solar System, d should be easily inside the green zone, g well outside in the blue and f just about on the edge of green and blue. Or is there some more detail going into defining those zones (e.g. different stellar spectrum)?.

Since these planets are likely tidally locked (same face facing the star), the temperature extremes will be larger. So liquid water could exist on the dark side of a planet that would normally be too close to the start, and likewise liquid water could exist on a planet's star-facing side even if it is further out. That seems to explain the larger than normal "goldilocks zone".
« Last Edit: 02/22/2017 08:13 pm by Lars-J »

Offline jebbo

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On the  comment from Andrew Page, he means Trappist-1f, but his main point stands: at a density of 0.6 +/- 0.17 that of Earth, it does suggest a volatile rich planet .. but that is not guaranteed.

Instead, there could be a rocky core with an extended H/He envelope but the core mass is too low to get a significant envelope (current theory say >1.5-1.6 Me for this to happen), so I'd say this is low probability.

The really great thing is that we will probably be able to find out soon!

--- Tony

Offline sanman

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Lords of Kobol! Could it be the Great Colonies?  :o

Offline Star One

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Lords of Kobol! Could it be the Great Colonies?  :o

Well Kepler is looking for more planets and it only has to find five more.
« Last Edit: 02/22/2017 08:54 pm by Star One »

Offline Star One

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The Earth-like planets of Trappist-1 already appear in sci-fi

Scientists say they've found the best place to search for life beyond our solar system. The first science fiction story about it has already been published, in the journal Nature.

https://www.cnet.com/news/nature-science-fiction-trappist-1-nasa-planets-laurence-suhner/

Offline ThereIWas3

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I was wondering if the gravitational interactions between all these closely spaced planets could create sufficient tidal forces on the ones with liquid water to create tides.  Some theories think that ocean tides from Earth's Moon had a role in the evolution of life, due to the sloshing at the edges.

Offline FutureSpaceTourist

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NASA's press conference:


Offline Bynaus

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Arxiv preprint on UV / XUV and habitability in the Trappist-1 system. Long story short, if there is an Earth-like moderately dense atmosphere with an ozone layer - all good. That failing, not even UV-resistant bacteria can make it.

https://arxiv.org/abs/1702.06936
More of my thoughts: www.final-frontier.ch (in German)

Offline sanman

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Arxiv preprint on UV / XUV and habitability in the Trappist-1 system. Long story short, if there is an Earth-like moderately dense atmosphere with an ozone layer - all good. That failing, not even UV-resistant bacteria can make it.

https://arxiv.org/abs/1702.06936

XRays won't penetrate far into the water - as long as you've got water oceans, you can have underwater life. Of course if you have that, then you probably have an atmosphere above it.

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