Planets studded with diamond mountains and filled with glass cores may be more than a psychedelic dream. A Jupiter-sized planet orbiting another star has a mostly carbon atmosphere, astronomers report online December 8 in Nature. The observation suggests that the rest of the planet may be mostly carbon, too.
The planet, WASP-12b, has an atmosphere containing at least twice as much carbon as scientists expected, an international team of researchers reports. This surprise invites new theories for how planets form, says astrophysicist Nikku Madhusudhan, a Princeton University astrophysicist who participated in the research while at MIT.
WASP-12b and its mother star, WASP-12, are 1,200 light-years from Earth. The planet is the size of Jupiter but at 2,500 kelvins, much hotter. Its orbit is only about one-fiftieth as far from its star as the Earth’s distance from the sun.
Using the Spitzer Space Telescope, Madhusudhan and colleagues recorded the infrared light from WASP-12b as the planet sneaks around its star. When the planet is in front of the star, the telescope records light from both the star and the planet’s atmosphere. When the planet is fully hidden behind the star, only the star’s light is recorded. Subtracting one measure from the other gives the light coming from just the planet.