Eccentric Exoplanet Gets Hot Flashes

Victoria Jaggard
National Geographic News
January 28, 2009

A distant Jupiter-like planet on an eccentric orbit swings so close to its parent star that its temperature spikes by about 1,260 degrees Fahrenheit (682 degrees Celsius) in only six hours, a new study reports.

Then as rapidly as it heats up, the extrasolar planet cools back down after zipping past its star, said lead study author Gregory Laughlin, an astronomer at the University of California, Santa Cruz.

The planet's path is unique, Laughlin noted. Most known "hot Jupiters" have tight, roughly circular orbits. They are tidally locked, showing only one face to their stars, just as the moon does to Earth.

(Related: "Half-Hot, Half-Cold Planets Have Supersonic Jet Streams" [October 20, 2008].)

"But this planet has the most eccentric orbit of any discovered," he said. Its elongated elliptical path makes it impossible for the world to be tidally locked, "so it's guaranteed to bring the planet spinning in every 111 days for a harrowing encounter."

The study is exciting, because it offers a glimpse at a very different kind of planet than most known worlds, said Heather Knutson, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA), who was not involved in the research.

And more data about this odd world can help scientists calibrate existing models for planetary climates, as well as find out whether they have a firm grasp on the fundamental physics of atmospheres, she said.

Fast and Furious

The exoplanet HD 80606b lies about 190 light-years away, orbiting a star in the constellation Ursa Majoris. It is roughly the same size as Jupiter but has four times the mass.

The planet was discovered in 2001 using a method that looks for the wobble in starlight created by a planet's gravity tugging on its host star.

In addition to showing that a planet is there, this method reveals details of its orbit and gives a minimum possible mass.

Due to its unusual path, HD 80606b spends most of its time about as far from its star as the midway point between Earth and Venus is from the sun. (Explore an interactive solar system.)

Continued on Next Page >>


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