For the first time, astronomers have directly observed the mysterious dark companion in a binary star system that has puzzled skywatchers since the 19th century. Using an instrument developed at the University of Michigan, scientists have taken close-up pictures of Epsilon Aurigae during its eclipse, which happens every 27 years.
Epsilon Aurigae is the fifth brightest star in the northern constellation Auriga. For more than 175 years, astronomers have known it is dimmer than it should be, given its mass. They also noticed its brightness dip for more than a year every few decades. They surmised that it was a binary system in which one companion was invisible. Because astronomers hadn't observed much light from it, the prevailing theory labeled it a smaller star orbited edge-on by a thick disk of dust. The theory held that the disk's orbit must be in precisely the same plane as the dark object's orbit around the brighter star, and all of this had to be occurring in the same plane as Earth's vantage point. This would be an unlikely alignment, but it explained observations.
The new images show that this is indeed the case. A geometrically thin, dark, dense, but partially translucent cloud can be seen passing in front of Epsilon Aurigae.
"It kind of blows my mind that we could capture this. There's no other system like this known. On top of that, it seems to be in a rare phase of stellar life. And it happens to be so close to us. It's extremely fortuitous." said John Monnier, an associate professor in the University of Michigan, Department of Astronomy.
The disk appears much flatter than recent modeling from the Spitzer Space Telescope suggests, Monnier said. "It's really flat as a pancake," he said.
