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imyourzer0 t1_je61740 wrote

I certainly don't know this bit, but I would assume that more complex molecules (which from what you're saying we know less about) are exponentially less likely. I say this mostly because the probability of finding element 1 and element 2 at some point in the universe is certainly less than the probability of finding just 1 or just 2. So, once you've dealt with all the combinations of two or three, whatever's left is unlikely to severely tilt the scales, unless that numbers game really reverses under some conditions. But, I take your point that if we can't describe larger molecules well, it's hard to say whether something more has its finger on the scale. Thanks for the answers!


adamginsburg t1_je66y45 wrote

Less likely, yes. Exponentially less, no. You'd be roughly right if molecule formation was just a matter of random chance associations, which is true in the diffuse ISM, but it is not true in dense clouds where molecules form. A large fraction of all molecules form in clouds that get cold enough that the molecules stick to the surfaces of solid (dust) particles. Once they're there, they're in rich company: there's hydrogen, carbon, oxygen, etc. in abundance - and then more "normal" chemical processes (i.e., things you might find happening on Earth) start to take over. So yes, the numbers game starts to reverse pretty hard!

Purely from gas-phase processes, though, you're basically right; we expect that most molecules with >5 atoms rarely form in the gas phase. We usually draw the line at methanol, CH_3OH, which is a bottleneck in the formation of more complex molecules.


imyourzer0 t1_je68is5 wrote

That’s pretty wild! Like we’ve all heard from Sagan that we’re made of star dust, but I never really thought I ought to be emphasizing the dust part much!

I’ve got a whole bunch more questions, but I’ll spare you—you’ve been more than patient enough.