Vega is a summer star in the Northern Hemisphere, visible toward the west at sunset. Vega is the brightest star in the constellation Lyra and, at only 25 light years away, quite close, cosmically speaking.
Due to its brightness, Vega has been used by astronomers as a touchstone to measure other stars' brightness for thousands of years - new findings say it may be more than 200 million years older than previously thought. The new estimation of Vega's age was made by more precisely measuring its spin speed with a tool called the Michigan Infrared Combiner, developed by John Monnier, associate professor of astronomy at the University of Michigan.
The Michigan Infrared Combiner (MIRC) collects the light gathered by six telescopes to make it appear to be coming through one that's 100 times larger than the Hubble Space Telescope. It's installed at the Georgia State Center for High Angular Resolution Astronomy Array located on Mt. Wilson, California. It boosts resolution so astronomers can zoom in, relatively speaking, to observe the shape and surface characteristics of stars that would otherwise look like mere points even through the most powerful telescopes. By tracking stars' surface characteristics, scientists can calculate how fast they rotate and deduce their inner workings.
About six years ago astronomers discovered that Vega is rotating so fast it's nearly flinging itself apart. They haven't been able to agree on many of the related details, however. One of the debates centers on Vega's exact rotation rate, which is essential to gauge both its mass and age. Other controversies deal with Vega's tilt as viewed from Earth and the amount of turbulence in the system from roiling gases at the star's surface.
Using MIRC, Monnier and colleagues have taken steps to rectify competing estimates of Vega's rotation rate and other properties The new findings indicate that the star rotates once every 17 hours, rather than once every 12. The sun's equator, for comparison, rotates much slower—once every 27 days, or 648 hours. In addition to finding that Vega is older than previously thought, the Michigan group confirmed its mass to be just over two times the sun's.
"Vega continues to challenge and surprise us," Monnier said. "We found out not too long ago that it has a disk of dusty debris, or a leftover solar system, around it. Then we found out it was a rapid rotator. It's a reference point for other stars, but it certainly isn't boring or normal."
Published in Astrophysical Journal Letters.