Summer star `Vega` 200-mn-yrs older than thought

Vega, a summer star in the Northern Hemisphere is just visible toward the west at sunset.

Washington: Vega, a star used by astronomers as a touchstone to measure other stars` brightness for thousands of years, may be more than 200 million years older than previously thought, scientists say.

Astronomers also found the mass of the star to be just over two times the Sun`s.

Vega, a summer star in the Northern Hemisphere is just visible toward the west at sunset. It`s the brightest star in the constellation Lyra. At 25 light years away, Vega is close on cosmic scales.

Researchers from the University of Michigan estimated Vega`s age by precisely measuring its spin speed with a tool called the Michigan Infrared Combiner (MIRC).

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.

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, scientists can calculate how fast they rotate and deduce their inner workings.

MIRC developed by John Monnier, associate professor of astronomy in U-M`s College of Literature, Science, and the Arts is installed at the Georgia State Center for High Angular Resolution Astronomy Array located on Mt Wilson, California.

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 centres 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.

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.

"Vega continues to challenge and surprise us. 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," Monnier said in a statement.

A paper on the findings is published in Astrophysical Journal Letters.