Fastest Stars In Galaxy Milky Way Have A Surprising Origin

Posted: Jul 8 2017, 4:18pm CDT | by , Updated: Jul 8 2017, 4:27pm CDT, in News | Latest Science News

Fastest Stars in Galaxy Milky Way have a Surprising Origin
Artist's impression of runaway stars. Credit: Amanda Smith

Incredibilty fast-moving hypervelocity stars came from a neighboring galaxy

An estimated100 billion stars reside in our galaxy Milky Way. Some of them are extremely fast-moving. They are known as hypervelocity stars. These stars travel so fast that they can leave our galaxy. Now, researchers have found that these incredibly fast-moving stars did not originate in Milky Way. They are actually the runaways from a small galaxy located in our neighborhood.

The speedsters originally belonged to the Large Magellanic Cloud (LMC), a dwarf galaxy orbiting the Milky Way. But explosion of one star in a binary system caused the others to fly off with such speed that it was able to escape the gravitational pull of their host galaxy and eventually made their way into our galaxy. Researchers have reached the conclusion after using data from the Sloan Digital Sky Survey and creating computer simulations.

“These stars have just jumped from an express train - no wonder they're fast," said co-author Rob Izzard from Institute of Astronomy. "This also explains their position in the sky, because the fastest runaways are ejected along the orbit of the LMC towards the constellations of Leo and Sextans.”

Currently, some 20 hypervelocity stars have been identified in the Milky Way and most of them are located in northern hemisphere. Astronomers suspect the number of stellar sprinters could be much higher than that.

“Earlier explanations for the origin of hypervelocity stars did not satisfy me,” said lead author Douglas Boubert from Cambridge's Institute of Astronomy. "The hypervelocity stars are mostly found in the Leo and Sextans constellations - we wondered why that is the case."

Another explanation is that they are runaways from binary star system, which means each of them had a companion. In a binary system, proximity of two stars determines their orbital speed. The closer the two stars are, the faster they orbit around each other. And if one star explodes as a supernova it can have profound effect on the speed of other stars and can put them on the path out of the galaxy.

"We are the first to simulate the ejection of runaway stars from the LMC - we predict that there are 10,000 runaways spread across the sky," said Boubert.

“The European Space Agency's Gaia satellite will report data on billions of stars next year, and there should be a trail of hypervelocity stars across the sky between the Leo and Sextans constellations in the North and the LMC in the South."

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