25 May 2010

Hottest planet ever being eaten by its star

Agençe France-Presse
It's the hottest planet ever discovered, hugging its parent star in a tight and fiery orbit that will eventually see it spin to a cataclysmic death, astronomers announced.
WASP-12b

Artist's concept of the exoplanet WASP-12b; the hottest known planet in the Milky Way galaxy, and potentially the shortest lived.

WASHINGTON DC: It’s the hottest planet ever discovered, hugging its parent star in a tight and fiery orbit that will eventually see it spin to a cataclysmic death, astronomers announced.

The doomed planet, dubbed WASP-12b, has the highest known surface temperature of any planet in the Milky Way – around 1,500 degrees Celsius, according to a paper published in The Astrophysical Journal Letters.

It could be enveloped by its own parent star over the next 10 million years, the paper’s authors have concluded.

Using a new instrument called the Cosmic Origins Spectrograph that was installed on Hubble in 2009, the researchers observed how the planet was whipped into an elongated shape by gravitational forces.

Captured by the star

“We see a huge cloud of material around the planet, which is escaping and will be captured by the star. We have identified chemical elements never before seen on planets outside our own Solar System,” said team leader Carole Haswell of The Open University in Britain.

While the planet is too far away for Hubble to photograph directly, but this interpretation is based in part on analysis of Hubble spectroscopic and photometric data.

Discovered in 2008, WASP-12b is located about 600 light-years from Earth in the Auriga Constellation, and is more than 300 times the size of Earth.

It is only 3.22 million km from its Sun-like parent star; just 2 percent of Earth’s distance from our Sun. Gravitational tidal forces from the star stretch the planet into an egg shape, and the planet is so hot that it has puffed up to the point where its outer atmosphere spills onto the star.

It also has a mass 40 percent greater than that of Jupiter, the biggest planet in our Solar System.

A year only 24 hours long

It is so close to its parent star that it orbits it in little more than 24 hours.

Astronomers already knew that stars will swallow a planet that comes too close to it, but this is the first time that the phenomenon has been observed so clearly.

The paper, which was published in the May 10 edition of The Astrophysical Journal Letters, confirms a theoretical paper published in the journal Nature last week by Shu-lin Li, an astronomer at Peking University in Beijing.

Shu-lin had predicted that the planet’s surface would be distorted by the star’s gravitational pull, and that gravitational tidal forces would make the interior so hot that it would greatly expand its outer atmosphere.

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