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I_eat_staplers t1_je1zuhx wrote

> very warm and dense, [...] NaCl in the gas phase

  • Sodium chloride/Boiling point: 2,669°F (1,465°C)

What kind of scale are you used to that this qualifies as "warm"?!

Fantastic discovery and response! This is incredibly interesting and certainly opens up a lot more questions.

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adamginsburg t1_je20qy1 wrote

That's the boiling point at atmospheric pressure. The NaCl we observed is likely not that hot - probably only ~100K but maybe 1000K (fig 6 of https://ui.adsabs.harvard.edu/abs/2019ApJ...872...54G/abstract shows that there's some ambiguity - we measure two temperatures and are not sure how to reconcile them!). We observe NaCl in an effective vacuum, so the boiling point (more likely sublimation point) is much lower. That said, it's possible that non-thermal mechanisms are responsible for releasing the NaCl into the gas phase - in other words, the gas isn't at the boiling point, but something knocked the NaCl molecules off the dust grains. Another possibility is that individual dust grains got very hot briefly, hot enough to vaporize, but again the gas isn't all that hot. We don't know for sure; we haven't yet come up with a consistent model to explain all the observations.

Just to give you a sense of boiling points: water transitions to gas at 373 K at atmospheric pressure. In the interstellar medium, it sublimates at closer to 100-150K.

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Metaphoricalsimile t1_je69847 wrote

I wonder if someone could set up an experiment to expose NaCl to an alpha flux (so simulated solar wind) and see how it changes the sublimation rate even at lower temperatures.

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scutiger- t1_je20ryr wrote

When talking about stars, the cold end is in the low thousands of degrees.

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Welpe t1_je3mau9 wrote

Scales get weird in physics. A week or two ago I was explaining just how cold helium needs to be to display superfluidity and ended up describing something like 25K as “balmy”, which it is compared to 2.1K or whatever it was for helium.

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