Worldbuilding

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.

This sounds like a good question for !askscience@lemmy.world

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.

Five days does seems right for reaching uninhabitable planet state. The soil would stay warm for quite a while longer, I imagine.