Yearlong Star Eclipse May Help Solve Space Mystery

While relatively few people were looking, an unusual eclipse darkened New Year's Day.

On January 1 a giant space object blotted out our view of Epsilon Aurigae, a yellow supergiant star about 2,000 light-years from Earth. Based on studies of Epsilon Aurigae's previous eclipses, astronomers expect the star won't fully regain its bright shine until early 2011.

Normally the star is so bright it can be seen with the naked eye even by city dwellers. For all but the most rural star-gazers, though, the mystery object that eclipses the star causes it to vanish for about 18 months every 27.1 years.

Ever since the star's periodic eclipses were first recorded in 1821, astronomers have been puzzling over how Epsilon Aurigae pulls off its lengthy disappearing act.

Now, "using data from the Spitzer Space Telescope, we've reached a solution to a nearly two-century-old mystery," study leader Don Hoard, of the California Institute of Technology, said today at an American Astronomical Association press briefing in Washington, D.C.

According to the new model, Epsilon Aurigae is a dying star being orbited by another star, and that stellar dance partner is cloaked in a wide disk of dark dust.

Based on the new Spitzer data, Hoard's team thinks the eclipse lasts so long because the dark disk is about 744,000,000 miles (1,197,351,936 kilometers) across—eight times as wide as the distance from Earth to the sun.