Exo-Planets

That is, planets orbiting around other stars. Phil Plait, in his blog "Bad Astronomy" at Slate, gives us the low-down on the latest research:

For example, you can use some statistics to extrapolate how many planets there must be in our galaxy. A new study has done just that, and the number they get is stunning: they calculate there may be a hundred billion planets in the Milky Way, with 17 billion of them the size of Earth!

Artwork depicting a multiple planetary system around a cool red dwarf star.

Now that's cool!