Water vapor has been detected in the atmosphere of one of the first alien planets ever identified by astronomers.
Advances in the technique used to scan the atmosphere of this "hot Jupiter" could help scientists determine how many of the billions of planets in the Milky Way contain water like Earth, researchers said.
The exoplanet Tau Boötis b was discovered in 1996, when the search for worlds outside our solar system was just kicking off. At about 51 light-years away, Tau Boötis b is one of the nearest known exoplanets to Earth. The planet is considered a "hot Jupiter" because it is a massive gas giant that orbits close to its parent star. [A Gallery of the Strangest Alien Planets]
To analyze the atmosphere surrounding Tau Boötis b, scientists looked at its faint glow. Different types of molecules emit different wavelengths of light, resulting in signatures known as spectra that reveal their chemical identify.
"The information we get from the spectrograph is like listening to an orchestra performance; you hear all of the music together, but if you listen carefully, you can pick out a trumpet or a violin or a cello, and you know that those instruments are present," study researcher Alexandra Lockwood, a graduate student at Caltech, explained in a statement.