Largest Known Planet Found, Has Density of Cork

August 8, 2007

The biggest alien planet found so far is baffling scientists with properties that defy current scientific explanation.

By all rights, TrES-4, a gas giant recently discovered about 1,400 light-years away in the constellation Hercules, shouldn't exist.

The planet's size is much larger than predicted for its mass, said Georgi Mandushev of Lowell Observatory, lead author of a new study on the exoplanet.

Though 70 percent bigger than Jupiter, TrES-4 contains only three-quarters of the red giant's mass. (Related: "First Proof of Wet 'Hot Jupiter' Outside Solar System" [July 11, 2007].)

That means the alien planet is about as dense as balsa wood or cork, said Mandushev, who is part of a planet-hunting team known as the Trans-Atlantic Exoplanet Survey.

"At this point the most valuable thing about this study is it presents a challenge to our theoretical models," Mandushev said. "Most advances in science come from confrontations just like this one."

The findings will be published in an upcoming issue of Astrophysical Journal Letters.

Hot Find

Peter McCullough leads another exoplanet discovery team, called the XO Project, from his position at the Baltimore, Maryland-based Space Telescope Science Institute.

Both he and Mandushev suspect that the unusually large size of TrES-4 has something to do with extreme heat.

The planet is only 4.5 million miles from its parent star, and it orbits in about three days, compared to Jupiter's 12-year revolution.

That means TrES-4 is superheated to about 2,300 degrees Fahrenheit (1,260 degrees Celsius).

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