Astronomers zoom in on Epsilon Aurigae's eclipse mystery

Star pictures captured by a new instrument developed at the University of Michigan (U-M) confirm that Epsilon Aurigae is eclipsed every 27 years by a pancake-flat dusk disk orbiting its companion star edge-on, in an unlikely alignment for a binary system.

Because Epsilon Aurigae appears dim for a star of its mass and dims even more every 27 years, astronomers had theorized that this fifth brightest star in the constellation Auriga (visible in the northern hemisphere), is a binary system where the star orbits a smaller star that is itself companioned by a thick dust cloud that eclipses the system periodically as it orbits. Scientists at the U-M Department of Astronomy developed an instrument that allowed astronomers from U-M, Georgia State University and the University of Denver to observe Epsilon Aurigae's mysterious dark companion directly for the first time during the system's latest eclipse cycle (2009-2011). The new images show the shape of the shadow cast by the dark object that has mystified observers for almost 200 years. The team's research, funded by the office of the dean of the College of Arts and Sciences at Georgia State University and the National Science Foundation, is presented in a paper titled "Infrared images of the transiting disk in the epsilon Aurigae System" published in the April 8 edition of the journal Nature. As reported on the Universe Today website, Epsilon Aurigae's 175-year-old eclipse mystery has been the focus of the Citizen Sky project. Associate professor John Monnier of the U-M Department of Astronomy, an author of the paper, remarked:

"This really shows that the basic paradigm was right, despite the slim probability. 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."

Monnier added that the dusty disk appears "flat as a pankake," much flatter than a recent modeling from the Spitzer Space Telescope suggested. Monnier led the team that engineered the U-M's Infra-Red Combiner (MIRC) instrument that was able to zoom in on the Epsilon Aurigae system using a process called interferometry that combines light from multiple telescopes. The MIRC combined and amplified light captured by four telescopes at the Center for High Resolution Astronomy (CHARA) array at Georgia State University, making the team's new Epsilon Aurigae images appear 100 times larger than Hubble Space Telescope images.