Banaras Hindu University diamond-studded stars

Astronomers led by Indian American Nikku Madhusudhan have discovered a giant planet with an atmosphere and core dominated by carbon, raising the prospect that diamond-studded stars may exist.

Madhusudan, a Banaras Hindu University (BHU) alumnus now at Princeton University, New Jersey, and his colleagues have observed that an extremely hot planet discovered last year has more carbon than oxygen - a feature never observed on a planet until now.

The planet, called WASP-12b, orbits a star about 1,200 light-years from Earth, and appears to have temperatures of nearly 2300°C - hot enough to melt stainless steel, the scientists said in the journal Nature.

A computational technique developed two years ago by Madhusudan while he was at the Massachusetts Institute of Technology (MIT), Cambridge, Massachusetts, was used to analyse the atmosphere of the planet.

Like Jupiter, WASP-12b is made largely of gas, only its core contains carbon-based minerals such as diamonds and graphite, said Madhusudhan now a postdoctoral scientist in the department of astrophysical sciences at Princeton.

"A carbon-rich planet has dramatic implications for its interior, its atmosphere, and may compel us to rethink our long-ingrained ideas of planetary formation," he said.

The planet-larger than Jupiter-is windy, blazing hot and so near its star that it circles in a single day compared with the 365 needed for Earth to go round the sun.

While one side of WASP-12b always faces the star and is daylit, and the other is always dark, the planet's strong winds and gaseous nature distribute energy and keep both sides equally warm.

With that much hotness and no solid surface, WASP-12b couldn't support life, Madhusudhan said. That doesn't mean that other carbon planets are devoid of life, he said.

"If life exists on such planets, it has to be able to sustain low oxygen, low water and lots of methane and other hydrocarbons" that would be in the atmosphere, he said.

If there are other planets with more carbon than oxygen, and some have rocky surfaces instead of gaseous ones, such orbs may have rocks made of diamonds and graphite, instead of silicon and oxygen found on Earth, Madhusudhan said, and sand there may be as rare as diamonds are on Earth.

Scientists used US space agency NASA's Spitzer Space Telescope to observe light emitted by the planet WASP12, discovered in 2009 by researchers in the UK-based consortium called Wide Angle Search for Planets.