How yellow supergiant star pulls off its lengthy disappearing act
By ANIWednesday, January 6, 2010
WASHINGTON - A team of astronomers has solved a nearly two-century-old mystery of how Epsilon Aurigae, a yellow supergiant star, pulls off its lengthy disappearing act.
On January 1, 2010, a giant space object blotted out our view of Epsilon Aurigae, which is about 2,000 light-years from Earth.
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,” said study leader Don Hoard, of the California Institute of Technology.
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.
Binary star systems have long been known to cause stellar eclipses as seen from Earth.
Epsilon Aurigae is unusual, though, because it has the longest lasting known eclipse.
The 18-month eclipse started last August, but it took the disk until now to fully obscure Epsilon Aurigae.
The new Spitzer data, combined with readings of other light waves from ground and space-based observatories, suggest that the star inside the disk is a B-type, a blue star three times as hot as our sun.
The model of a large but low-mass star orbited by a B star shrouded in dust matches the centuries of data collected so far on Epsilon Aurigae - potentially explaining once and for all how the long, strange eclipse is possible. (ANI)
