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New hypervelocity star discovered by Utah-led team

Published May 7, 2014 9:48 pm

Space • Breakthrough could provide new clues to mysterious dark matter.
This is an archived article that was published on sltrib.com in 2014, and information in the article may be outdated. It is provided only for personal research purposes and may not be reprinted.

A new hypervelocity star discovered by a University of Utah-led team is the closest and one of the brightest of its kind identified so far and could help shed new light on the mysterious dark matter that makes up a large part of our galaxy.

The new star is moving at more than 1 million mph, about three times faster than average. Scientists believe it got started on its high-speed path by a supermassive black hole at the center of the Milky Way.

It once was part of a pair of stars but detached from its partner after the two got too close to the black hole.

"The black hole has really strong gravity," explained Zheng Zheng, an assistant professor at the U. and lead author of a study published in Astrophysical Journal Letters by a team of American and Chinese astronomers. "When the pair of stars moves closer to the black hole, the gravity is so strong ... it makes the two stars separate from each other."

One of the stars was drawn into the black hole's orbit — or possibly sucked inside — and the other catapulted into space at tremendous speed. It's now been traveling for some 32 million years and is in the Milky Way's halo of dark matter.

"Dark matter is totally different from the matter we're familiar with," Zheng said. "We have knowledge of dark matter from its gravitational effect on other objects [but] ... we don't know what it is."

Astronomers can learn more about the substance by monitoring the star's position and watching how its motion is affected.

The star can also tell researchers more about the black hole that originally created it, Zheng said.

"So far, this star is the nearest, so it's very easy to do follow-up study," he said. It's one of about 20 hypervelocity stars that have been found during the past decade.

Even though the new star, dubbed LAMOST-HVS1, is the closest one to Earth, it's still about 249 quadrillion miles from this planet. (A quadrillion is 1 million billion).

Astronomers discovered the star using the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, which is 110 miles northeast of Beijing.

With a 13.1-foot-wide aperture, the telescope captures light-wavelength readings of up to 4,000 stars at once. These "spectra" can show researchers the stars' velocity, temperature, luminosity and size.

The new star is nine times more massive than our sun, but researchers say the chances of the black hole hurling a star toward Earth are low. It creates a hypervelocity star only once every 100,000 years, and the possible trajectories of stars nearby don't appear to pose any danger.

lwhitehurst@sltrib.com

Twitter: @lwhitehurst