Photos of distant planets put astronomers in orbit

The planet's existence had been suspected since 2005, when Kalas studied a picture of a dust ring around the star. He noticed the inner edge of the ring was sharply defined, raising his suspicions that there was something hiding there with a lot of gravity. Planets tend to sweep their orbits clean, either by ejecting pretenders or smashing them to dust.

When he studied a new picture, taken in 2006, he found an object in the dust belt. Comparing the two pictures, he determined that it was indeed orbiting the star.

"The gravity of Fomalhaut b is the key reason that the vast dust belt surrounding Fomalhaut is cleanly sculpted into a ring and offset from the star," Kalas said. "We predicted this in 2005, and now we have the direct proof."

The planet would not be capable of supporting life as we know it. At 11 billion miles from its star, about three times as far from its sun as Pluto is from ours, it would be too frigid.

Fomalhaut b, at between one and three Jupiter masses, is the lowest-mass planet yet found outside our solar system, Chiang said, and its discovery brings the day closer when researchers might be able to find Earth-like planets.

The planet has some surprising characteristics. For one thing, it is bluish, rather than the redder hue scientists expected.

"Both discoveries are causing us to re-question what a planet is," Sara Seager, a planetary scientist at the Massachusetts Institute of Technology, said at the news conference.

The second team, which included researchers from Lawrence Livermore, UCLA and the NRC Herzberg Institute of Astrophysics in Canada, took its photographs in infrared light.

Two breakthroughs made this discovery possible. First was the use of adaptive optics -- a set of optical techniques that correct for the interference of Earth's atmosphere, which bends and twists incoming light. In recent years, adaptive optics has become so sophisticated that ground telescopes can take pictures nearly as eye-popping as those from Hubble. Because the mirrors of Gemini and Keck are so large, 26 and 32 feet across, they can gather even more light.

Scientists estimated the three planets were seven to 10 times the size of Jupiter, just under the 13-Jupiter-mass-limit that scientists believe separates planets from brown dwarfs, which are failed stars. Like Fomalhaut b, they are far from their parent star, ranging from 24 to 67 astronomical units. An astronomical unit is the distance from Earth to the sun, about 93 million miles.