Peking University, Beijing, April 10, 2010: A group of astrophysicists from Peking University and other countries have determined that a massive planet outside our Solar System is being distorted and destroyed by its host star — a finding that helps explain the unexpectedly large size of the planet, WASP-12b.
This discovery not only explains what’s happening to WASP-12b; it also means scientists have an one-of-a-kind opportunity to observe how a planet enters the final stage of its life. "This is the first time that astronomers are witnessing the ongoing disruption and death march of a planet," says UC Santa Cruz professor Douglas N.C. Lin. Lin is a co-author of the new study and the founding director of the Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University, which was deeply involved with the research. Their findings have been published in Nature (February 25th).
The research was led by Li Shulin from the National Astronomical Observatories of China. A graduate of KIAA, Li and a research team analyzed observational data on the planet to show how the gravity of its parent star have been both inflating the planet’s size and spurring its rapid dissolution.
WASP-12b, discovered in 2008, 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. 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 miles. It is also larger than astrophysical models would predict. Its mass is estimated to be almost 50% larger than Jupiter's and its 80% larger, giving it six times Jupiter's volume. It is also unusually hot, with a daytime temperature of more than 2500°C.
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 Earth and the Moon cause sea levels rise and fall twice a day. However since WASP-12b is so close to its host star the gravitational forces are enormous. The tremendous tidal forces acting on the planet have completely changed the shape of the planet into something similar to that of an American football.
Edited by: Connie Chang
Translated by: Su Juan
Source: PKU News (Chinese)
