* Astronomy

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RE: Epsilon Aurigae

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Scientists find cause of mysterious solar eclipse

Scientists working at Georgia State's Centre for High Angular Resolution Astronomy have captured images that reveal the cause of what was previously a mysterious type of eclipse in the Epsilon Aurigae double star system.
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First image of star's eclipse

The first close-up image of an eclipse beyond the solar system has been captured by scientists.
Astronomers at the University of St Andrews worked on an international study of the star Epsilon Aurigae, from the Auriga constellation.
Every 27 years it becomes dimmer, a phenomenon which lasts for two years.
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Astronomers on Wednesday said they may have explained the riddle of a dimming star that has perplexed skygazers for nearly two centuries.
Located 2,000 light years from Earth in the northern constellation Auriga where it is one of the brightest stars, Epsilon Aurigae has triggered controversy ever since astronomers first noted in the 1820s that its light bizarrely halved in intensity for 18 months.
The phenomenon was later found to occur once every 27.1 years, sparking theories about what was the cause.
Suspicions centred on an eclipse -- some dark companion that swung between the distant star and Earth.
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Dark disk seen passing in front of star

U.S. astronomers have observed a thin, dark cloud passing in front of a distant star, helping explain a mysterious eclipse first observed in the 19th century.
Epsilon Aurigae is a visible star about 2,000 light years away in the constellation Auriga, the charioteer. Since at least the 1840s, astronomers have known that something passes in front of the star every 27 years, making it appear dimmer.
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By the time of the last eclipse, in the early 1980s, Don Hoard says astronomers had come up with two competing models of the Epsilon Aurigae system. Everyone agreed that there were two stars, and the dimmer, smaller star was surrounded by an obscuring cloud. But no one could figure out the nature of the larger star - the one we actually see in the sky at night.
One model described it as a supergiant star, 20 times the mass of our sun, the kind of star that eventually becomes a supernova.

"And the other theory is that the eclipsed star, this big bright one, was essentially a dying star, something with much lower mass, about two times the size of our sun, and a star that's on its way out the door" - Don Hoard, California Institute of Technology.

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For almost two centuries, humans have looked up at a bright star called Epsilon Aurigae and watched with their own eyes as it seemed to disappear into the night sky, slowly fading before coming back to life again. Today, as another dimming of the system is underway, mysteries about the star persist. Though astronomers know that Epsilon Aurigae is eclipsed by a dark companion object every 27 years, the nature of both the star and object has remained unclear.
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Centuries-Old Star Mystery Coming to a Close

For almost two centuries, humans have looked up at a bright star called Epsilon Aurigae and watched with their own eyes as it seemed to disappear into the night sky, slowly fading before coming back to life again. Today, as another dimming of the system is underway, mysteries about the star persist. Though astronomers know that Epsilon Aurigae is eclipsed by a dark companion object every 27 years, the nature of both the star and object has remained unclear.
Now, new observations from NASA's Spitzer Space Telescope -- in combination with archived ultraviolet, visible and other infrared data -- point to one of two competing theories, and a likely solution to this age-old puzzle. One theory holds that the bright star is a massive supergiant, periodically eclipsed by two tight-knit stars inside a swirling, dusty disk. The second theory holds that the bright star is in fact a dying star with a lot less mass, periodically eclipsed by just a single star inside a disk. The Spitzer data strongly support the latter scenario.
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