This eclipse happens every 27 years, lasting for about 18 months each time.
John D. Monnier, University of Michigan
THE GIST:
- A 190-year-old cosmic mystery over what causes Epsilon Aurigae's dimming has been resolved.
- A shroud of dust is blocking light from the companion star.
- The mystery was solved thanks to a network of infrared telescopes.
For nearly 190 years, scientists have argued over what's causing a bright, relatively nearby star known as Epsilon Aurigae to lose its luster every 27 years.
The dimming, which lasts about 18 months, is due to some sort of eclipsing companion. The most likely scenario, however, seemed ridiculously far-fetched: a sibling star of some sort cloaked in a shroud of dark dust and orbiting head-on relative to Earth.
Yet that's exactly what astronomers found using a network of four linked, infrared telescopes to create an instrument that can resolve targets with 100 times the power of the Hubble Space Telescope. The technique, called interferometry, allowed scientists to watch the companion object's silhouette pass across the face of Epsilon Aurigae, confirming the pair's unusual geometry.
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"If this thing was tipped another 10 degrees, you wouldn't even know it was there," Villanova University astronomer Edward Guinan told Discovery News. "It's just an accident."
"Interferometry is relative new, so hopefully this is the beginning of many more images to come," added University of Michigan astronomer John Monnier.
Scientists have two main theories about what's happening to Epsilon Aurigae and its companion.
Under the first model, both objects are large, sun-like stars. However, Epsilon Aurigae, being somewhat more massive than its twin, is developing faster. The disk around its partner is matter that was shed as the larger star expanded and cooled into a red giant. Under this model, the smaller, shrouded partner will continue to grow, albeit at a slower rate, until one day it emerges from its cover, perhaps shifting dust back to Epsilon Aurigae, which would have become a white dwarf star by then.
The other theory states that Epsilon Aurigae is a true massive supergiant, quite young in astronomical terms -- less than 5 million years old. The disk would be a remnant of star formation, not unlike the planetary disk that gave rise to our solar system.
In this scenario, it's possible that there are planets forming around Epsilon Aurigae's companion, but they won't have long to live. If Epsilon Aurigae is as massive as this model suggests, it will supernova in 20 million to 30 millions years, wiping out its companion in the process.
Observations of the star will continue throughout the remainder of the eclipse. Scientists are particularly keen to find out if there's a hole in the disk, as some computer models suggest.
"This is the first time a star has been imaged do this, so that's a neat thing," Guinan said.
The findings are reported in this week's issue of Nature.
Tags: Stars, Telescopes, Universe
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