The discovery was made using NASA's Spitzer Space Telescope in tandem with ground-based observations, a release Wednesday from NASA's Jet Propulsion Laboratory in Pasadena, Calif., said.
"This planet reveals the astounding diversity of worlds out there," Nikku Madhusudhan of the Massachusetts Institute of Technology says. "Carbon-rich planets would be exotic in every way -- formation, interiors and atmospheres."
The distant planet, dubbed WASP-12b, might harbor graphite, diamond, or even a more exotic form of carbon in its interior, beneath its gaseous atmosphere, researchers say.
Astronomers don't currently have the technology to observe the cores of planets orbiting stars beyond our sun, but their theories hint at these intriguing possibilities.
Earth has rocks mostly based on silicon and oxygen plus other elements. A carbon-rich rocky planet could be a very different place, scientists say.
"A carbon-dominated terrestrial world could have lots of pure carbon rocks, like diamond or graphite, as well as carbon compounds like tar," Joseph Harrington of the University of Central Florida, principal investigator of the research, says.
"When the relative amount of carbon gets that high, it's as though you flip a switch, and everything changes," Marc Kuchner, an astronomer at NASA's Goddard Space Flight Center in Greenbelt, Md., says. "If something like this had happened on Earth, your expensive engagement ring would be made of glass, which would be rare, and the mountains would all be made of diamonds."
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