DU Astronomers Help Solve a Celestial Mystery

Epsilon Aurigae is one of the brightest stars in the night sky.

Part of the constellation Auriga, it also is the star of its own mystery. Every 27 years the star appears to “blink.” For two to three years it visibly fades, eclipsed by an unknown orbiting body. For 190 years, scientists have speculated on the nature of that body, wondering if Epsilon Aurigae was being eclipsed by a hyper-extended infrared star, a black hole or a disk-shaped cloud of matter.

Thanks largely to the efforts of astronomy Professor Robert Stencel and PhD candidate Brian Kloppenborg, the mystery has been solved.

Working with teams from the University of Michigan and Georgia State University, Stencel proposed combining inferometric imaging equipment and software developed at Michigan with Georgia State’s giant array of telescopes in California to create an image of the eclipse 2,000 light years away. Racing against time—especially in-demand telescope time—and almost thwarted by fires and mudslides near the Mount Wilson Observatory, the team captured the first real images of Epsilon Aurigae’s mysterious space companion in fall 2009.

Their findings and images were published in the April 8, 2010, issue of the journal Nature.

It turns out that Epsilon Aurigae, the diameter of which is about 300 times that of Earth’s sun, is obscured by a solar-system-sized, disk-shaped dust cloud perfectly oriented vis-à-vis Earth and the star to create the observable eclipse.

The discovery confirmed many recent hypotheses, said Stencel, who has been dogging Epsilon Aurigae since his years at NASA in the 1980s. “Astronomers have known about dark disks, but here we’ve obtained direct, bona fide evidence. It’s only through technological advances that such a picture could be made in a cogent way.”

As with any breakthrough, this one raises new questions: What is the disk made of? And is it a planetary system about to be born? To learn more, Stencel and Kloppenborg will return to DU’s Meyer-Womble Observatory atop Mount Evans, where they will monitor eclipses and delve into new mysteries.