July 16, 2005 in Nation/World

Giant planet found that has three suns

Robert S. Boyd Knight Ridder

WASHINGTON – “Star Wars” fans know all about Tatooine, Luke Skywalker’s home planet, whose two suns glare down on a vast desert.

Now comes an even more extraordinary, real-life sight: a newly discovered giant planet with three suns wheeling overhead.

The Jupiter-sized world is 149 light-years (about 879 trillion miles – just next door for astronomers) away from Earth in a triple-star system in the northern constellation Cygnus, or the Swan.

Maciej Konacki, a planetary scientist at the California Institute of Technology in Pasadena, reported the sighting in this week’s edition of the British scientific journal Nature.

“With three suns, the sky view must be out of this world, literally and figuratively,” Konacki said.

About 150 extrasolar planets have been discovered in the past 10 years. About 20 of them were found in binary star systems, consisting of two suns, but this is the first time a planet has been found in a cluster of three.

The main star of the trio, named HD 188753, is slightly larger than our sun. But it would look enormous to an observer on the planet, which whirls around its host star every 3 1/2 days at a distance of only about 4 million miles. Our sun, 93 million miles away, looks much smaller.

Unlike Tatooine, life would be impossible on the newly discovered planet, since its temperature is estimated to be a scorching 1,340 degrees Fahrenheit, Konacki said in an e-mail message.

The other two stars, each somewhat smaller than our sun, spin around each other at a distance of about 850 million miles, the distance from the sun to Saturn in our solar system.

The biggest star would appear yellow, the next largest would be orange and the smallest one red. “The environment in which this planet exists is quite spectacular,” Konacki said.

He used the 32-foot-wide Keck One telescope on the Mauna Kea volcano in Hawaii to make his discovery. He detected tiny wobbles in the motion of HD 188753 as the gravity of its companions yanked it this way and that.

The discovery of the planet challenges current theories about the formation of giant planets around other stars.

Most astronomers think such planets form in huge disks of gas and dust around young stars. But a gang of three stars would destroy most of the disk before the planet could form, Konacki said.

HD 188753 is “a conundrum” for theorists, two German astronomers, Artie Hatzes and Gunther Wuchterl, wrote in a commentary piece in Nature. “This planet should not exist.”

But it does.

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