Astronomers Discover Earth-Sized Planets Engulfed By Star
December 22, 2011

Astronomers Discover Earth-Sized Planets Engulfed By Star

Astronomers report that they have discovered two Earth-sized planets circling a dying star that has passed the red giant stage.

The planets have been engulfed by their star due to it swelling up to a red giant and dying out.

The discovery could help shed new light on the destiny of stellar and planetary systems, such as our own solar system.

Once the sun reaches the end of its life cycle in about 5 billion years, it will swell up to a red giant.  A red giant is an inflated star that has used up most of its fuel.

When the sun reaches this stage, it will grow to its outer edges and will swallow the innermost planets, including Mercury, Venus, Earth and Mars.

"When our sun swells up to become a red giant, it will engulf the Earth," Elizabeth Green, an associate astronomer at the University of Arizona's Steward Observatory, said in a press release. "If a tiny planet like the Earth spends 1 billion years in an environment like that, it will just evaporate. Only planets with masses very much larger than the Earth, like Jupiter or Saturn, could possibly survive."

The two newly discovered planets have migrated so close to their star that they are probably deep into the star's envelope during the red giant phase.  However, the researchers believe that they have survived.

The host star, KOI 55, consists of the exposed core of a red giant that has lost nearly its entire envelope.  The researchers say the planets may have contributed to the increased mass loss necessary for formation of this subdwarf B star.

The team believes that planetary systems may influence the evolution of their parent stars.  They said the planetary system they observed offers a glimpse of the future of our own solar system.

The astronomers obtained data with the NASA Kepler mission to study the star.  They published their findings in the journal Nature on Thursday.


Image Caption: Two planets that survived the red-giant expansion of their host star. Illustration by Stéphane Charpinet/Institut de Recherche en Astrophysique et Planétologie in Toulouse, France.


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