The diamond as big as a planet

Posted by Emma Woollacott

It's a long way to go, but it could be worth it: most of the rocks on an odd gas giant 1,200 light years away could be made of diamond, astronomers say.

They've found that there's more carbon than oxygen in the atmosphere of WASP-12b, indicating that rocks throughout the planet would be made of pure carbon, in forms such as diamonds or graphite. It may even have a diamond core. It's the first carbon-rich world ever observed.

"On most planets, oxygen is abundant. It makes rocks such as quartz and gases such as carbon dioxide," says University of Central Florida professor Joseph Harrington. "With more carbon than oxygen, you would get rocks of pure carbon, such as diamond or graphite, and lots of methane gas."

The team performed a chemical analysis of data from NASA's Spitzer Space Telescope, comparing the infrared behavior of common gases to determine the composition of the planet's atmosphere.

Researchers were surprised to find methane, a trace gas on Earth, in the searing-hot temperatures found on the planet.

"This is new territory with implications in several areas, from planetary formation and interiors to astrobiology,” says lead author Nikku Madhusudhan of Princeton University.

While carbon is of course a key building block of life, WASP-12b doesn't look particularly habitable, to say the least. It's so close to its star that its year is just 26 hours, and daytime temperatures hit 4,700 degrees Farenheit. It's also being torn apart by the gravitational force of its star.

WASP-12b was discovered
last year by a UK consortium, the Wide Angle Search for Planets.