Rochester Review
March–April 2010
Vol. 72, No. 4
Story as a PDF
Departments
In Review
There’s more to the Big Dipper than meets the eye.
In ancient times, people with exceptional vision discovered that one of the brightest stars in the Big Dipper was, in fact, two stars so close together that most people cannot distinguish them. The two stars, Alcor and Mizar, were the first binary stars—a pair of stars that orbit each other—ever known.
Now Rochester astronomer Eric Mamajek has discovered that Alcor, one of the most studied stars in the sky, is actually two stars. Mamajek, an assistant professor of physics and astronomy, led a team that made the discovery using computer algorithms to remove as much glare as possible from the image of a star in the hopes of spotting a planet near the star.
“Finding that Alcor had a stellar companion was a bit of serendipity,” says Mamajek. “We were trying a new method of planet hunting and instead of finding a planet orbiting Alcor, we found a star.”
Modern telescopes have found that Mizar is itself a pair of binaries, revealing what was once thought of as a single star to be four stars orbiting each other. Alcor and its newly identified companion, Alcor B, are apparently gravitationally bound to the Mizar system, making the whole group a sextuplet.
Mamajek is continuing his efforts to find planets around nearby stars, but his attention is not completely off Alcor and Mizar.
“Some of us have a feeling that Alcor might actually have another surprise in store for us,” he says.
—Jonathan Sherwood ’04 (MA), ’09S (MBA)
