First Earth-sized planets spotted
21 December 2011 Last updated at 17:09 GMT
Astronomers have discovered the first Earth-sized planets, which are orbiting a star similar to our own Sun.
It's thought that the planets are now too hot for anything to survive on them, but scientists believe they would've once been cool enough for life to exist.
The planets have been called Kepler 20f and Kepler 20e because they were found by Nasa's Kepler telescope.
Check out Joe's report to find out more.