Diamond Planet
October 11, 2012

Nearby Super-Earth Is A Diamond Planet

Lee Rannals for redOrbit.com - Your Universe Online

One nearby super-Earth planet could have a lot more "bling" on it than our planet, because astronomers say it maybe a diamond planet.

Yale University scientists reported in the Astrophysical Journal Letters that the surface of 55 Cancri e is likely covered in graphite and diamond, rather than water and granite.

The planet has a radius twice of Earth's, and a mass eight times greater, allowing it to fall into the classification "super-Earth."

It is one of five planets that orbit the star 55 Cancri, which is located 40 light years from Earth and is visible to the naked eye in the constellation Cancer.

A year on Earth is 365 days, but a year on 55 Cancri e lasts just 18 hours. It is also considerably hotter than Earth, with a temperature of about 3,900 degrees Fahrenheit.

Astronomers were able to measure the planet's radius last year for the first time as it transited its star. This information allowed the Yale scientists to determine its chemical composition using models of its interior, and by computing all possible combinations of elements and compounds.

Astronomers previously reported that the host star has more carbon than oxygen, and the team confirmed that large amounts of carbon and silicon carbide, and a negligible amount of water ice, were available during the planet's formations.

They also believe that 55 Cancri e contains super-heated water, according to lead researcher Nikku Madhusudhan. However, new research indicates that the planet has no water at all, and is composed mostly of carbon, iron, silicon, carbide and some silicates.

The study authors concluded that at least a third of the planet's mass could be made of diamond. This would mean that the amount of diamonds 55 Cancri e holds is about three times Earth's mass.

“By contrast, Earth´s interior is rich in oxygen, but extremely poor in carbon – less than a part in thousand by mass,” said co-author and Yale geophysicist Kanani Lee.

The research indicates that a carbon-rich super-Earth could be far more alien than previously thought when considering chemical constituents, interiors, atmospheres or biologies similar to Earth.

A carbon-rich composition could influence the planet's thermal evolution and plate tectonics, with implications for volcanism, seismic activity and mountain formation.

“Stars are simple – given a star's mass and age, you know its basic structure and history,” said David Spergel, professor of astronomy and chair of astrophysical sciences at Princeton University. “Planets are much more complex. This ℠diamond-rich super-Earth´ is likely just one example of the rich sets of discoveries that await us as we begin to explore planets around nearby stars."

Madhusudhan led the first discovery of a carbon-rich atmosphere in a distant gas giant planet last year. This research opened up the possibility of long-theorized diamond planets.

The latest research represents the first time astronomers identified a likely diamond planet around a sun-like star. Follow-up observations of the planet's atmosphere and additional estimates of the stellar composition would strengthen the findings about the planet's chemical composition.

Image 2 (below): Illustration of the interior of 55 Cancri e – an extremely hot planet with a surface of mostly graphite surrounding a thick layer of diamond, below which is a layer of silicon-based minerals and a molten iron core at the center. Credit: Haven Giguere