U.S. astronomers have discovered a planet unlike any other known in the universe. Smithsonian scientists say the new planet was discovered using a network of small automated telescopes known as HATl. The planet -- designated HAT-P-1 -- orbits one member of a pair of distant stars 450 light-years away in the constellation Lacerta.

"We could be looking at an entirely new class of planets," said Gaspar Bakos, a Hubble fellow at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

With a radius about 1.38 times that of Jupiter, HAT-P-1 is the largest known planet. But, in spite of its huge size, its mass is only half that of Jupiter.

"This planet is about one-quarter the density of water," Bakos said. "In other words, it's lighter than a giant ball of cork! Just like Saturn, it would float in a bathtub if you could find a tub big enough to hold it."

Astronomer Robert Boyes, co-discoverer of the planet, said, "This new discovery suggests something could be missing in our theories of how planets form."

Bakos is lead author of a paper submitted to the Astrophysical Journal describing the discovery.

Copyright 2006 by United Press International