planet_found_020108 WASHINGTON D.C. - Astronomers have found evidence for the first known planet orbiting a giant star that is aged and swollen the way our Sun will one day be, hinting that planets can survive the latter stages of a star's life.
Over the past five years or so, astronomers have found about 80 extrasolar planets. All are large, some several times the mass of Jupiter. Until today, none had been spotted around very large stars.
The new discovery, presented here today at a meeting of the American Astronomical Society, involved a star called iota Draconis, which is 13 times larger than the Sun.
"Until now, it was not known if planets existed around giant stars," said Sabine Frink, a post-graduate researcher at the University of California, San Diego. "This provides the first evidence that planets at earthlike distances can survive the evolution of their host star into a giant."
The planet orbits iota Draconis once every 1.5 years and so is thought to be at a distance similar to Earth's distance from the Sun. But the planet is nothing like Earth. It is probably made mostly of gas and is at least 8.7 times the mass of Jupiter, the researchers say, though it could be much larger.
Frink made the find with the help of a seasoned team of planet hunters using a method that has been used to discover most other planets outside our solar system. The technique does not actually see planets. It notes the wobble of a host star caused by the gravitational pull of a planet.
The method cannot determine an upper limit to the planet's mass.
Earth's fate
The discovery is likely the first in a line of findings -- expected over the next few years with the help of improved techniques and new space-based telescopes -- that will help scientists sort out the fate of Earth and the rest of our solar system.
A few billion years from now, the Sun will swell into a giant star. Earth will be bathed in 60 times more radiation than today, and temperatures will rise to several hundred degrees. Scientist don't agree on exactly what will happen, but the
prospects are grim across the theoretical board."The oceans will evaporate, and the water vapor will escape Earth's atmosphere," said Andreas Quirrenbach, a U.C. San Diego researcher who was also on the team that made the discovery.
Ongoing research aims to determine the exact nature of the planet.
"Observing the fate of this companion to a dying star is a reminder of the ultimate fate of our own Earth," said Debra Fischer, a team member from U.C. Berkeley. Researchers Geoffrey W. Marcy of U.C. Berkeley and Paul Butler of the Carnegie Institution were also involved in the finding.
The star iota Draconis is 100 light-years from Earth in the constellation Draco. It is visible with the naked eye in the morning sky, just east of the Big Dipper.
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