But with one star system, Gliese 581, we may have hit the jackpot. To look at Gliese 581 in the sky, it doesn’t look like much.
It’s a red dwarf star, and a much smaller star than our own Sun. It weighs in at only about 30% of the mass and size of our Sun, and it’s estimated to be twice as old. But at only 20 light-years from us, it’s pretty close, for another star.
So what makes it so important?
Now, this planet that we found is very close in, just 3% of the distance to its star that the Earth is from the Sun, which makes it like an extreme version of Mercury.
But, planet Gliese 581 d looks like it is habitable, and rocky, just like Earth is. It’s at the right distance from its star to get the right temperatures and conditions for life.
And remember, these four planets that we’ve found are — probably — just the four biggest ones. They are, respectively, 16, 7, 5, and 2 times the mass of Earth; the last three are expected to be rocky planets! Who knows how many lower-mass, Earth-sized planets are there, and where they might be located? I would keep an eye on this system if I were you, because it is the closest, best hope we have right now for life outside of our Solar System!
And with a minimum age of these planets of 7 billion years, you can bet that if life did form there, it’s probably awfully interesting by now…