Author Topic: NASA's Trappist-1 Announcement - Feb 22, 2017  (Read 55372 times)

Offline CuddlyRocket

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

[In the spirit of the suggestion. :) ]
Presumably you mean a name for the star? (TRAPPIST-1 is a catalog designation.) The system would then be called 'the [name of star] system'!

The IAU Working Group on Star Names might go for Axanar. The only two catalog designations I can find are 2MASS J23062928-0502285 and the later TRAPPIST-1 suggesting the star was discovered in the Two Micron All-Sky Survey of 1997-2001. So, there's unlikely to be any of the traditional or historical names for which the WGSN has a preference. The WGSN might object though if they consider a name from the title of a fan-made Star Trek movie to be a name of a principally commercial nature. Also, the film concerns the 'Battle of Axanar' and the WGSN also prohibit names related to military activities!

Offline Bynaus

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

[In the spirit of the suggestion. :) ]
Presumably you mean a name for the star? (TRAPPIST-1 is a catalog designation.) The system would then be called 'the [name of star] system'!

The IAU Working Group on Star Names might go for Axanar. The only two catalog designations I can find are 2MASS J23062928-0502285 and the later TRAPPIST-1 suggesting the star was discovered in the Two Micron All-Sky Survey of 1997-2001. So, there's unlikely to be any of the traditional or historical names for which the WGSN has a preference. The WGSN might object though if they consider a name from the title of a fan-made Star Trek movie to be a name of a principally commercial nature. Also, the film concerns the 'Battle of Axanar' and the WGSN also prohibit names related to military activities!

Yes, the name of the star. Although, I was not thinking of "Axanar" as a name (that might be an idea too!), its just that from the first moment "many planets, all habitable" somehow rang a bell - until I remembered where I had heard the phrase before. At the time-index I linked (or tried to link), they talk of the "Inverness" system, five inhabited planets, rich in dilithium and considered holy ground by the Klingons. :) I am sure CBS would argue that Axanar is principally commercial. ;)

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.

Good point. There might be a problem retaining the atmosphere, though. But we'll soon (my guess: before SpaceX lands humans on Mars!) learn much more about these atmospheres!

The system is only about 500 Ma old, so biogenic O2-rich atmospheres/ozone layers seem not very likely anyway.
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Offline high road

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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

And here I was thinking life predated the ozone layer by 1.5 billion years.

Offline the_roche_lobe

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Quote
The system is only about 500 Ma old, so biogenic O2-rich atmospheres/ozone layers seem not very likely anyway.

That number is only a very rough minimum. The age of extremely long lived M dwarfs is notoriously hard to pin down because they evolve so slowly. The star could be billions of years old, especially because it seems to be a quiet star flare-wise.

P

Offline Ben the Space Brit

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I was thinking about the inverse square law the other night. Would closer orbits necessarily mean far greater proportional exposures to high-frequency photons? So, irrespective of their relative output levels, M-type dwarves thermal habitability zones would be automatically more likely to be far more hazardous in terms of ionising radiation?
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Offline jebbo

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That number is only a very rough minimum. The age of extremely long lived M dwarfs is notoriously hard to pin down because they evolve so slowly. The star could be billions of years old, especially because it seems to be a quiet star flare-wise.

On the other hand, it has a high metallicity ([Fe/H] = +0.04), which suggests it can't be *too* old. Similarly, it has a fast rotation rate. But as you say, 0.5 billion is a minimum. It could easily be a few billion.

--- Tony
 
« Last Edit: 02/23/2017 04:16 pm by jebbo »

Offline CuddlyRocket

That number is only a very rough minimum. The age of extremely long lived M dwarfs is notoriously hard to pin down because they evolve so slowly. The star could be billions of years old, especially because it seems to be a quiet star flare-wise.

On the other hand, it has a high metallicity ([Fe/H] = +0.04), which suggests it can be *too* old. Similarly, it has a fast rotation rate. But as you say, 0.5 billion is a minimum. It could easily be a few billion.

What is needed is radiometric dating of the rocks of the planets and other objects in this stellar system - though this is a touch beyond our current technology! :)

Offline sghill

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I was thinking to myself that this solar system model may be giving us a glimpse of what planetary systems look like in the absence of a gas giant that cleans smaller rocky bodies out of the inner orbital space.


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).


"H" is for Hoth. :)

« Last Edit: 02/23/2017 05:38 pm by sghill »
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Offline Star One

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By the way there's a special Google Doodle today celebrating this discovery.

IAU really need to give this star a proper name.
« Last Edit: 02/23/2017 01:28 pm by Star One »

Offline Machdiamond

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Great job on the public outreach, it has been a big hit on mainstream media around the world (front page of my newspaper this morning).
It has its own website: http://www.trappist.one/

Offline jebbo

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I was thinking to myself that this solar system model may be giving us a glimpse of what planetary systems look like in the absence of a gas giant that cleans smaller rocky bodies out of the inner orbital space.

The speckle imaging rules out anything from 0.32 AU to about 14 AU, so I was thinking more that this is maximal use of the initial disc ... to me it feels much more a scaled up Jovian system than a scaled down Solar System, and I'm thinking of "b" as an Io analogue.

There is just so much still to learn. Very exciting times!!!

Oh, and typo fixed :-) and on metallicity, I want to see a more detailed breakdown ... in particular, Li.

--- Tony

Offline Star One

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Here's an interesting post from Centauri Dreams.

Quote
Greg Laughlin is always worth reading. Here’s the relevant paragraph from his post today:

“2MASS J20362926-0502285, now much better known as TRAPPIST-1, straddles the boundary between the lowest mass main sequence stars and the highest mass brown dwarfs. Depending on precisely what its mass and metallicity turn out to be, it could either be arriving at self-sustaining core hydrogen fusion, which would make it a main sequence star (about a 60% chance) or it could be currently achieving its peak brown dwarf luminosity and bracing for a near-eternity of cooling into obscurity (about a 40% chance).”

Also quite interesting here is his take on the future of this system, assuming TRAPPIST-1 is indeed a main sequence star:

“An object with solar composition and 0.08 solar masses never turns into a red giant. As time goes on, it maintains a near-constant radius, and slowly burns nearly all of its hydrogen into helium. In roughly 10 trillion years, TRAPPIST-1 will reach a maximum temperature of ~4000K, pushing it briefly toward K-dwarf status for a few tens of billions of years, before eventually running out of fuel and fading out as a degenerate helium dwarf.”

http://www.centauri-dreams.org/?p=37204

Offline JasonAW3

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An interesting thought has occurred to me.

      With M class dwarf stars, it's pretty much assumed that planets in the habitable zone would likely be tidally locked.  (I suspect that this also assumes no large mass satellite companion)  As was mentioned in the press briefing, these planets are close enough in their orbits that they tend to tug on each other as they pass on another.

      I would think, with this interaction, that, if each world has an initial rotation, that the tidal forces acting on each planet, would tend to maintain a certain amount of rotation of each planet, while still providing tides to what ever atmosphere and/or surface liquids, that might exist on those planets.

      My reasoning is based largely upon the current Earth/Luna tidal interaction that has slowed Earth's rotation from 10 hour days initially, to 24 hour days over 4.5 billion years.  In this case, rather than slow down the rotation of each planet, the various planets interacting with each other would help maintain a more or less average rotation rate for each, based upon each orbital position and each planet's interaction with the others.

      This would also imply a certain level of tidal heating of each planet's core, which could, in theory, help to produce magnetic fields for each planet, depending on the metallic content of each planet's core.

      Of course, I could be wrong, but this does make a certain amount of sense to me.
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Offline Star One

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What impact could larger planets such as gas and ice giants further out in the system have on the habitability of these rocky worlds?
« Last Edit: 02/23/2017 06:41 pm by Star One »

Offline Hungry4info3

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An interesting thought has occurred to me. ...

That's not quite how it works. The star is, by far, the dominant tidal influence on the planet's rotation states.
Test your idea though: The mass ratio of TRAPPIST-1 to its planets is about the same as that of Jupiter to its moons, Saturn to its moons, and Uranus to its moons, with rather similar levels of compactness (Jupiter being somewhat less of course).

What are the rotation states are the moons of Jupiter, Saturn, and Uranus?

(Also, I suspect the torque on a planet's rotation by a passing planet would probably average to zero, given circular orbits)
« Last Edit: 02/23/2017 09:02 pm by Hungry4info3 »

Offline JasonAW3

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An interesting thought has occurred to me. ...

That's not quite how it works. The star is, by far, the dominant tidal influence on the planet's rotation states.
Test your idea though: The mass ratio of TRAPPIST-1 to its planets is about the same as that of Jupiter to its moons, Saturn to its moons, and Uranus to its moons, with rather similar levels of compactness (Jupiter being somewhat less of course).

What are the rotation states are the moons of Jupiter, Saturn, and Uranus?

(Also, I suspect the torque on a planet's rotation by a passing planet would probably average to zero, given circular orbits)

From what was said at the news conference, it seems that these planets have enough of an influence on each other tospeedupand slow down each other's orbits.  Fortunately, the resonance of the orbits seem to keep the whole system stable.

But I'd still like it if someone could run the numbers.  Most likely you're correct, but this doesn't exclude the possibility that some of those planets might have moons of a similar size ratio as the Earth and moon.  (I think it's exceedingly unlikely, given the push and pull that these planets seem to have with one another, but still, possible I suppose).
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Offline Hungry4info3

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So the problem with massive moons around tidally locked planets is that the Hill sphere radius will always be much, much smaller than the synchronous orbit radius. Therefore *all* moons will orbit the planet faster than the planet rotates. The tides will bring the two objects together, pretty quickly if the moon is reasonably massive.

Large moons cannot exist around any of the detected TRAPPIST-1 planets, even before you consider planet-planet interactions.
« Last Edit: 02/24/2017 02:14 am by Hungry4info3 »

Offline Archibald

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By the way there's a special Google Doodle today celebrating this discovery.

IAU really need to give this star a proper name.

https://en.wikipedia.org/wiki/Trappists
Han shot first and Gwynne Shotwell !

Offline jebbo

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A paper on the Hubble observations of Trappist-1:

Reconnaissance of the TRAPPIST-1 exoplanet system in the Lyman-α line
https://arxiv.org/abs/1702.07004

Key quote from the conclusions:
Quote
[W]ater vapor in the upper atmosphere could photo-dissociate and sustain an outflow of escaping hydrogen. The stellar Ly-α line is bright enough to perform transit spectroscopy, and we detect marginal flux decreases in localized, high-velocity ranges during the transit of planet b, and shortly after the
transit of planet c. This could hint at the presence of extended hydrogen exospheres around the two inner planets, and suggest that atmospheric escape might play an active role in the evolution of all TRAPPIST-1 planets.

--- Tony
« Last Edit: 02/24/2017 08:30 am by jebbo »

Offline sghill

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What impact could larger planets such as gas and ice giants further out in the system have on the habitability of these rocky worlds?

They can help clear out devastating comets, asteroids, dwarf, and proto-planets from impacting the inner planets.

Personally, I think the shear volume of inner planets in resonant orbits indicates there are no gas giants in that system (see my previous post) unless they are verrrry far out. It (they) would have swept some of those inner worlds clear.



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