Update (Feb. 21, 2007): Two papers are online describing these results. They're technical, but if you're interested: one on HD 189733b and one on HD 209458b.
Astronomers using the orbiting Spitzer Space Telescope have, for the first time, seen the emission spectrum from planets orbiting another star! This is extremely cool, as you'll see.
First off, a spectrum is what you get when you break up light into its individual colors. Think of it like a rainbow, but with a lot more colors. By carefully examining the brightness of each color, you can tell a lot about the object giving off that light -- for example, its temperature, its chemical composition, and even how it's moving. In this case, astronomers used Spitzer to examine the spectra of two planets in the infrared, light invisible to the naked eye. Many interesting molecules emit infrared light, so it's a good wavelength to ...
