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Planet discovered orbiting around red giant star

Iota Draconis system in an artist's concept.
Iota Draconis system in an artist's concept.  

By Richard Stenger
CNN Sci-Tech

(CNN) -- Astronomers announced this week that they spotted the first planet orbiting a giant star, a find that could offer a tantalizing glimpse into the fate of the Earth.

While scientists have identified a host of other planets around other stars, this one is unique in how different its parent star is compared with the sun, astronomers said.

Iota Draconis has burned through its hydrogen fuel and become a red giant, boasting a radius 13 times greater than the sun. The transition is common for many stars as they approach death.

"Until now, it was not known if planets existed around giant stars," said Sabine Frink of the University of California at San Diego, who, with colleagues, presented the findings at a meeting of the American Astronomical Society.

"This provides the first evidence that planets at Earthlike distances can survive the evolution of their host star into a giant," Frink said.

Iota Draconis resides about 100 light-years away in the constellation Drago, just east of the Big Dipper. Its planet completes a highly elliptical orbit about once every 1.5 years and has an estimated mass about nine times that of Jupiter.

The planet was identified using the indirect wobble technique, whereby astronomers measure its gravitational tug on its parent star. Its true mass could be slightly higher, in which case it might be a brown dwarf, a middling object between stars and planets.

The sun will likely become a red giant. And astronomers have long wondered which planets in our solar system will survive the change. If the Earth hangs on, it will not be pretty.

Our comfortable home will endure about 60 times more radiation, pushing the temperature up at least twice as high as the boiling point of water. The oceans will evaporate and the water vapor will escape the atmosphere because of the sizzling heat, the astronomers said.

"Observing the fate of this companion to a dying star is a reminder of the ultimate fate of our own Earth," said one of the researchers, Debra Fisher of the University of California at Berkeley.

Earth has time to bide before the calamity. Our middle-aged sun will not balloon into its terminal phase for several billion years.




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