Host star destroying massive extra-solar planet: Astronomers

Last Updated: Thursday, February 25, 2010 - 19:23

Beijing: A recently discovered extra-solar
planet, which is nearly double of Jupiter`s volume, is being
distorted and destroyed by its host star, giving an exclusive
opportunity to astronomers to observe how a planet enters
final stage of its life.

An international group of astronomers has found that a
massive planet `WASP-12b`, which was discovered in 2008, is
being distorted and destroyed by its host star, Science Daily

"It`s a discovery that not only explains what`s
happening to WASP-12b; it also means scientists have a
one-of-a-kind opportunity to observe how a planet enters this
final stage of its life," said Douglas N C Lin from the Kavli
Institute for Astronomy and Astrophysics (KIAA) at Peking
University, Beijing.

"This is the first time that astronomers are witnessing
the ongoing disruption and death march of a planet," said Lin,
co-author of the findings published in journal Nature today.

WASP-12b is one of the most enigmatic of 400-plus
planets that have been found outside our solar system over the
past 15 years. It orbits a star, in the constellation Auriga,
roughly similar in mass to our sun, said lead author Shu-lin
Li from the National Astronomical Observatories of China.

It is also larger than astrophysical models would
predict. Its mass is estimated to be almost 50 per cent larger
than Jupiter`s and 80 per cent larger than Jupiter`s volume.
It is also unusually hot, with a daytime temperature of more
than 2500 degree C.

Like most known extra-solar planets, it is large and
gaseous, resembling Jupiter and Saturn in this respect, but
unlike Jupiter, Saturn or most other extra-solar planets, it
orbits its parent star at extremely close range -- 75 times
closer than the earth is to the sun, or just over 1 million

Some mechanism must be responsible for expanding this
planet to such an unexpected size, say the researchers. They
have focused their analysis on tidal forces, which they say
are strong enough to produce the effects observed on WASP-12b.
On earth, tidal forces between the earth and the moon
cause local sea levels rise and fall modestly ll twice a day.

WASP-12b, however, is so close to its host star that the
gravitational forces are enormous.

The tremendous tidal forces acting on the planet
completely change the shape of the planet into something
similar to that of a rugby football.

These tides not only distort the shape of WASP-12b. By
continuously deforming the planet, they also create friction
in the its interior. The friction produces heat, which causes
the planet to expand.

"This is the first time that there is direct evidence
that internal heating (or `tidal heating`) is responsible for
puffing up the planet to its current size," Lin added.

Huge as it is, WASP12-b faces an early demise, say the
researchers. In fact, its size is part of its problem. It has
ballooned to such a point that it cannot retain its mass
against the pull of its parent star`s gravity.


First Published: Thursday, February 25, 2010 - 19:23

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