First, you would have to find a way to land on its surface (which would be on the nucleus itself, since, investigating, I found that it is the only entirely solid part of the planet). Once on the surface, we would have to understand that light is not capable of passing through cloudy bodies, which is what makes up most of the planet’s surface.
So, putting that data together, the view of the night sky from Jupiter’s surface would hopefully be extremely cloudy (and probably ocher and reddish in color). The most you could see would be the lightning that is produced in its endless thunderstorms, cyclones and anticyclones, but I doubt that outer space is visible from its surface (if we compare its colorful atmosphere with ours, which looks like glass).
What did the sky look like in the Paleolithic era (2.5 million years ago)? Was the sun more or less bright? Were there more clouds? What was the night sky like?
Two and a half million years, astronomically enough, is quite a bit.
Certainly the Sun shone on average somewhat less, approximately 0.01%, but absolutely negligible. The Moon was a little closer and a little bigger, but not significantly. The day lasted about a minute and a half less, it was not remarkable for the lives of our ancestors.
Regarding the climate, it depended on the zones, deserts such as the Sahara or the Atacama were very similar to the current ones, the same as the humid tropical zones. In middle or polar latitudes, it depended on the precise moment, 2.5 million years ago cooling climatic cycles began that made the climate colder and cloudier for long intermittent periods.
The constellations would be unrecognizable, although some large and not especially close stars, say Deneb, were already visible and similar to today, others, like Sirius, were much further away than they are today and did not stand out especially. The ones that were seen, on average, looked a lot like the current ones. The vision of the planets, essentially identical to the current one. Distant objects such as galaxies or globular clusters, were also seen in almost the same positions as now.
If a current person were transported to that time without instruments, astronomically, he would only realize it by the changed constellation figures.
Why is Jupiter not a star when some stars are smaller than it?
Jupiter would need to be about 75 times its current mass to get hot enough to initiate nuclear fusion reactions in its core. There is simply no way for a body less than this mass to fuse ordinary hydrogen (protium) into helium. A “brown dwarf” of about 13 times the mass of Jupiter or more can fuse deuterium (Hydrogen-2) into helium, and one of 62 masses or more can fuse lithium, but it takes about 75 times the mass of Jupiter to merge the protium and become a star proper. Massive brown dwarfs stop fusing when they run out of deuterium and / or lithium.
There are stars about the size of Jupiter, but they are much denser because they are much more massive. White dwarfs, the cores of dead stars, are much smaller than Jupiter, but their nature is very different from that of a young star or protostar, and it is not really part of this discussion.
Red dwarf stars close to the minimum mass for proto-stratum fusion will be the longest-lived stars of all. Despite their low mass compared to other stars, they fuse their hydrogen very slowly and are fully convective, allowing them to fuse all available hydrogen. Because of this, they can survive on the main sequence for about 14 billion years.
How do you know if Jupiter has mountains if you can’t see them?
It is impossible to see mountains, because their atmosphere is so dense and so opaque that they cannot reach the core of the planet even with the most powerful radar.
Of course many years ago I read that the core of the planet was liquid nitrogen or hydrogen. But I think that there is no way of knowing. I believe that nothing prevents us from imagining that this planet has a nucleus similar to that of the earth, but that we have no way of knowing. I imagine by analogy to rocky planets that the reason for having so much atmosphere is that it started with a rocky planet 10 or 20 times the mass of the earth. I think all the gaseous planets started out as rocky planets, but large. The high gravity of these planets made them capture a large amount of gas. And that’s why they are called sodas.