Credit: NASA/JPL-Caltech/R. Hurt (SSC)

This artist's concept shows the searing-hot gas planet WASP-12b (orange orb) and its star. NASA's Spitzer Space Telescope discovered that the planet has more carbon than oxygen, making it the first carbon-rich planet ever observed. Our planet Earth has relatively little amounts of carbon -- it is made largely of oxygen and silicon. Other gas planets in our solar system, for example Jupiter, are expected to have less carbon than oxygen, but this is not known. Unlike WASP-12b, these planets harbor water, the main oxygen carrier, deep in their atmospheres, where it is difficult to measure.

Concentrated carbon can take the form of diamond, so astronomers say that carbon-rich gas planets could have abundant diamond in their interiors.

WASP-12b is located roughly 1,200 light-years away in the constellation Auriga. It swings around its star every 1.1 days. Because the planet is so close to its star, the star's gravity stretches it slightly into an egg shape. The star's gravity also pulls material off the planet into a disk around the star (shown here in transparent, white hues).