Extrasolar planets are getting a lot more interesting. After finding hundreds of "hot Jupiters" -- big balls of gas orbiting close to their parent stars -- astronomers are discovering a more diverse population, including some worlds that aren't much bigger than Earth. They're also discovering more systems that have several planets.
An example of that is HD 10180, a Sun-like star that's about 125 light-years away. At least five planets orbit the star, and perhaps as many as seven. The larger number would make HD 10180 the largest planetary family outside the solar system discovered to date.
Most of its planets are about as massive as Neptune, the third-heaviest planet in the solar system. But there's evidence that one planet isn't much heavier than Earth. It's not Earth-like, though -- it's so close to the star that its surface is red hot.
One planet that may be slightly more hospitable orbits the star GJ 1214. The planet is only a few times bigger and heavier than Earth, so it's most likely a ball of rock like Earth is.
Astronomers recently discovered an atmosphere around the planet. The atmosphere either contains a lot of steam, or it's topped by a thick layer of clouds.
This planet, too, is too hot for life as we know it -- at least at the surface. But here on Earth, life inhabits some pretty unfriendly places, so we can't rule out the possibility that life could survive below the surface of this intriguing planet.
Script by Damond Benningfield, Copyright 2010