gg_account t1_jdxenq8 wrote on March 27, 2023 at 10:00 PM

This is actually pretty puzzling. B was thought to have the thickest atmosphere of all the planets because of its low apparent density. This could mean all the planets have underestimated densities, or maybe their composition on a whole is very different from our solar system.

FlingingGoronGonads t1_jdzw1dp wrote on March 28, 2023 at 12:33 PM

Some red dwarfs are known to have very turbulent flare activity, so I'm not entirely surprised (although I don't know if this is the case for TRAPPIST-1).

Not trying to be a chauvinist here, but when it comes to understanding planets, astrophysics isn't the be-all and end-all, or planetary science wouldn't exist. Planetary atmospheres are very complex, even simple (and ephemeral) ones like Mercury's, for example.

gg_account t1_je09zma wrote on March 28, 2023 at 2:20 PM

Makes me wonder if B has an atmosphere but it's all frozen into a giant glacier on the night side.

worldbuilding_Curls t1_jdzwe5w wrote on March 28, 2023 at 12:36 PM

Isn't Trappist 1 supposed to be an ultra-cool red dwarf tho?

I mean it still has flares more powerful than Sun, but it is relatively calm.

HerderOfZues t1_je0iseu wrote on March 28, 2023 at 3:18 PM

There is also a counter-argument to the activity of red dwarves. Most planetary systems are on the same axis as the star rotation, the axis of rotation has a lot less direct activity that would be constantly blasted at the planets and mainly happens at the poles. So there is still possibility that even active red dwarves can have habitable planets or planets that it didn't completely strip the atmo off

FTL_Diesel t1_je0c1y0 wrote on March 28, 2023 at 2:34 PM

This has changed a bit. More recent analyses of the TTVs in the system put all the Trappist planets right on the line for Earth/Venus-like composition. See Figure 12 here: https://arxiv.org/abs/2010.01074

gg_account t1_je0pbaf wrote on March 28, 2023 at 4:00 PM

Interesting thanks! The data I was looking at was apparently from 2018. So it seems the jump to "there must be a thick atmosphere" came from an assumption that the planet had as much iron as Earth?

FTL_Diesel t1_je17m5v wrote on March 28, 2023 at 5:55 PM

The observation planning assumed that -1b would have an atmosphere similar to Venus. This is why they observed five eclipses, since a Venus-like atmosphere would have been just detectable after combining all that data. What ended up happening is that the dayside of the planet is much hotter than predicted for a Venus-like atmosphere, and the eclipse was actually detected right off the bat on the first observation!