Tag Archives: hypervelocity stars

Fastest stars in Milky Way escaped from Large Magellanic Cloud?

Astronomers have proposed that the fastest stars in Milky Way actually escaped from the Large Magellanic Cloud (LMC), the largest nearby satellite dwarf galaxy.

The LMC is the largest and fastest of the dozens of dwarf galaxies in orbit around the Milky Way. It only has 10% of the mass of the Milky Way, and so the fastest runaways born in this dwarf galaxy can easily escape its gravity. The LMC flies around the Milky Way at 400 kilometres per second and, like a bullet fired from a moving train, the speed of these runaway stars is the velocity they were ejected at plus the velocity of the LMC. This is fast enough for them to be the hypervelocity stars. “These stars have just jumped from an express train – no wonder they’re fast,” said co-author Rob Izzard, a Rutherford fellow at the 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.”

Their calculations predict how many hypervelocity stars should be detectable and where in the sky they should be. If right, the data from Gaia, soon to be released, should prove them right or wrong.

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Astronomers announced today the discovery of several dozen stars which are traveling so fast they will escape the Milky Way galaxy.

Astronomers announced today the discovery of 18 sunlike stars which are traveling so fast they will escape the Milky Way galaxy.

These sunlike stars are in addition to another 20 blue giant stars that are also traveling at escape velocity.

The origin of all of these new stars is completely mysterious. The theory had been that such stars got their speed boost by being flung past the galaxy’s central supermassive black hole, dubbed Sagittarius A* (pronounced “A-star”). These new stars, however, come from other directions, and in fact appear to have even come from outside the galaxy’s main disk. Thus, astronomers are baffled as to what caused them to be traveling so fast.

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