How long do you think it would take the atmosphere to cool to the point of precipitating if the sun were to vanish?
25d 5h ago by lemmy.world/u/early_riser in worldbuilding
From what I remember, most (all?) of the heat in the atmosphere, or at least in the troposphere, comes from the ground, with convection carrying heat into the upper atmosphere.
Looking at my temperature graph from my weather station in my backyard, overnight the temp dropped about 1 Freedom Unit per hour. So at the absolute quickest, and assuming an average surface temperature of 60 F when the sun vanishes, here's what I have
| Atmospheric gas | melting point (F) | hours until gas begins condensing | days until gas begins condensing |
|---|---|---|---|
| water | 32 | 28 | 1.166666667 |
| CO2 | -70 | 130 | 5.416666667 |
| argon | -307 | 367 | 15.29166667 |
| N2 | -346 | 406 | 16.91666667 |
| O2 | -361 | 421 | 17.54166667 |
This is likely way too fast, as I believe the colder you are, the less heat you lose. Also, melting/boiling points depend on the surrounding pressure, which will get effected by the other gases precipitating. 70 below isn't unheard of, and the coldest temp ever reached was -128 in Antarctica.
What do you think. IDK I'm le tired.
This sounds like a good question for askscience@lemmy.world
Yeah but I want this community to have more content.
When I'm not running on fumes I should probably look up radiative cooling. Some quick googling says it would take a week for the ocean surface to start freezing, and be -100F by a month or so. But this is for Earth. A terraformed dwarf planet would probably take much less time.
A Deepness in the Sky, by Vernor Vinge, explores this question with a star that goes dark every 50 years. Seems like it would depend upon the planetary specifics, i.e. atmosphere composition and volcanic activity. You could have a great telescope afterwards.
This sounds to me like a question that could be answered using Universe Sandbox.
So, loading up the default solar system, here's Earth:
(note the temperature and gas pressure maps on the left)
Now, lets delete the Sun:
I'm setting the sim speed to 1 hour/second, so that I can see what's going on. Aaand hit play.
... it's much slower than I expected. I'm pretty sure the temperature sim was not meant for this, because after one simulated month, the average surface temperature has only dropped by about 2.5 °C. That sounds very wrong. (There is unfortunately no option to show the atmosphere's temperature.)
So ... the only significant difference is a slight temperature change, and (if you look at the liquid depth map) most of the northern hemisphere has been covered in a few millimeters to centimeters of liquid (maybe this is actually the atmosphere?). But gas pressure still looks mostly normal. Maybe I should file a bug report.
That’s absolutely a bug. Temps dip more substantially even overnight. Assuming there’s no temperature advection during the night, the low is hit just before dawn. No dawn means no rising temperature.
Yeah, running it a bit longer (and much faster), it took a bit more than 150 years for the atmosphere to liquify.
Five days does seems right for reaching uninhabitable planet state. The soil would stay warm for quite a while longer, I imagine.