Vega Older Than Thought, Astronomers Say

According to an international group of astronomers led by Dr Peter Tuthill of the Sydney Institute for Astronomy, Vega – the brightest star in the constellation Lyra located about 25 light-years away – may be more than 200 million years older than previously thought.

This is an artist’s impression of planets orbiting the star Vega (David Hardy)

The group used a tool called the Michigan Infrared Combiner and installed at the Georgia State Center for High Angular Resolution Astronomy Array on Mt. Wilson in California to estimate the age of Vega by precisely measuring its spin speed. The tool collects the light gathered by six telescopes to make it appear to be coming through one that’s 100 times larger than NASA’s Hubble Space Telescope.

The tool 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, astronomers 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.

The astronomers have taken steps to rectify competing estimates of Vega’s rotation rate and other properties.

The findings, published in the Astrophysical Journal Letters (arXiv.org version), indicate that Vega rotates once every 17 hours, rather than once every 12. In addition to finding that Vega is older than previously thought, the group confirmed its mass to be just over two times the Sun’s.

“Vega continues to challenge and surprise us,” said Prof John Monnier of the University of Michigan, lead author on the AJ paper.

“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.”

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Bibliographic information: J. D. Monnier et al. 2012. Resolving Vega and the Inclination Controversy with CHARA / MIRC. ApJ 761, L3; doi: 10.1088/2041-8205/761/1/L3