By Patricia Daukantas

For the past year, “citizen scientists” have been observing the behavior of an unusual double star to gain insight into its mysterious eclipses. Recently, a team of professional astronomers used optical interferometry to catch the first glimpse of the dimmer star that eclipses its brighter companion every 27.1 years.

As we’ve blogged in the past, the star system Epsilon Aurigae has been the subject of an intensive observing campaign this year. Several of the professional astronomers behind the “citizen sky” project have now seen that the eclipsing object is a large, slightly tilted disk surrounding a single, hot star. The team reported its results in the April 8 issue of Nature.

It turns out that the central star of the pair is a F-type star, slightly hotter than our Sun and with up to three times its mass, and its eclipsing companion is an extremely hot B-type star, shrouded in dust warmed to about 550 K. But how do Robert Stencel (University of Denver, Colo., U.S.A.) and his colleagues know that?

As it turns out, they imaged the Epsilon Aurigae system with the CHARA array of six telescopes on Mount Wilson in California. (CHARA stands for the Center for High Angular Resolution Astronomy, located at Georgia State University in Atlanta.)

With apertures of only 1 m, the six CHARA scopes are tiny by professional standards. However, they are positioned over the mountainside to provide the resolving capability of a much larger single telescope – up to 331 m wide (that’s the array’s longest baseline). Radio astronomers may have been the first to use interferometry to boost the amount of detail we can see in the heavens, but optical (visible and infrared) astronomical interferometry has come of age in recent years – see this post about another interferometer on Mount Wilson, used by OSA Honorary Member Charles Townes and colleagues to study the size of the red giant star Betelgeuse.

For more information on CHARA and optical interferometry, see this PDF presentation or the CHARA website. For additional coverage of Epsilon Aurigae, see the U.S. National Science Foundation announcement or this article from Sky & Telescope magazine.

And don’t forget … the Citizen Sky website is still collecting observations of Epsilon Aurigae, and anyone can make them regardless of equipment (or the lack thereof). This makes a great class project.

2010-04 April, Astronomy, Astrophysics amateur astronomy, astronomy, interferometry, citizen sky, astrophysics, optical interferometry