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Sun's Wayward Twin Discovered
By Dave Mosher
Staff Writer
posted: 09 November 2007
02:47 pm ET

Somewhere out there, astronomers knew the sun had another long-lost relative aimlessly drifting through the Milky Way. Now they've found it.

Although a happy reunion is unlikely, as the star HIP 56948 is about 200 light-years away, it is now considered to be the best "solar twin" out of four known candidates.

The wayward star challenges the idea that our backyard star has a unique composition, as it has a similarly low quantity of the element lithium--a lightweight byproduct of the fusion reactions that power stars.

Astronomers Jorge Melendez of the Australian National University and Ivan Ramirez of the University of Texas at Austin discovered the new star with a telescope at the McDonald Observatory in Texas. The mid-sized star is one of many in the Draco the dragon constellation and may be a billion years older than the sun, which is middle-aged at 4.6 billion years.

Three other solar twins were previously proposed: 18 Scorpius, HD 98618 and HIP 100963. While similar to the sun in many ways, spectrographic analysis revealed that their lithium contents are dramatically higher.

Because of those observations, astronomers wondered if the sun's low amount of lithium was unique. The newfound twin now shows that it isn't.

Searches for solar twins are important, the astronomers said, because the sun is used as a baseline for many other types of studies. But our own solar power plant is too close and too bright to study like distant stars.

The solar twins discovered at McDonald should help astronomers study the chemical compositions of stars and back theoretical models of our sun's stellar insides and evolution with real observations.

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