This solar eclipse happens only once every 27 years, and John Monnier was there to see it.
Epsilon Aurigae is a star system about 2,000 light years from Earth. Astronomers have been able to see it for nearly two centuries, and noticed that it dims every 27 years or so. It made sense to assume that they were dealing with a binary star system, with a larger primary star and a smaller secondary star circling around the first. But that didn’t answer all their questions. Why, for instance, did the primary star normally appear dimmer than it should? And if there is a smaller star orbiting the main star, why can’t we see it? To explain that, astronomers developed the unlikely theory that a thick disk of dust was orbiting the smaller star in the same plane as the smaller star’s orbit of the larger star [UPI].
Monnier says he first felt there was a slim probability that this explanation—a secondary star shrouded in dust—was true. To find out for sure, Monnier and his colleagues needed to catch the eclipse when the smaller star passed in front of the larger, and capture really telling images. That’s just what they did. The astronomers used the Michigan Infra-Red Combiner instrument to combine the light entering four telescopes at the CHARA array at Georgia State University. The effect is a virtual telescope that is much larger than its four constituents [Space.com].
The results, published in Nature, were staggering to Monnier. Despite the improbability of the explanation, there was indeed a “thin, dark, dense, but partially translucent cloud” passing in front of the star in the infrared pictures. Monnier says: “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” [Space.com].
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Image: John Monnier