One of the most interesting star systems to me is Trappist-1. Basically it's a ridiculously small red dwarf star (about the size of Jupiter) with 7 planets around it. The reason I find it fascinating isn't because the individual planets but because of the individual planets but because of the nature of the system itself. A lot has happened since early 2017 when it was first discovered, and although there are certainly problems with the possibility of life on each of the planets, the fact that most of them have even a slight chance of bearing life adds up to something very interesting. For the elephant in the room, Trappist-1 is a red dwarf, which is usually bad. The star's habitable zone is EXTREMELY close to it. This is because it's about as cool as stars get. About 2,000 degrees. The reason this is so bad is because the closer you are to a star, the more radiation you'll be exposed to. But this is pretty much the only place in the Trappist-1 system where Earth-like planets can exist. If a planet was far away from the star and didn't have to worry about radiation, it would be far outside of the habitable zone. In order for a planet to have a reasonable chance to have liquid water (at least on its surface) is for it to be in the habitable zone, where it would be bathed in ultraviolet radiation, which isn't very good for life if you couldn't guess. Another issue is that red dwarves are very active stars. Active meaning they have much larger and more frequent solar flares than Sol. Solar flares are harmful because they destroy atmospheres. This doesn't spell doom for the Trappist-1 planets, but it does mean they would probably need to have very strong magnetospheres to shield them from solar flares. This may seem to greatly decrease the chances of these planets being habitable, but keep in mind that it is completely normal to find exoplanets with problems, and that we haven't found any exoplanets so far that even come close to being the same as Earth.