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Milky Way’s Fast-Moving Galactic Hypervelocity Stars Come from another Galaxy | ASHARQ AL-AWSAT English Archive 2005 -2017
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The barred spiral galaxy NGC 6872 in the Milky Way, Jan 10,
2013. Photo: Reuters/NASA

London- A new study conducted by the University of Cambridge pointed out that the fastest stars in the Milky Way Galaxy may be ‘runaways’ from other galaxies.

DPA Agency reported the results of the study run by a team of astronomers led by Douglas Boubert, and published in the Monthly Notices of the Royal Astronomy Society.

Astronomers know that stars have their own motion, however, this is usually only observed over periods separated by long intervals, because of the enormous distances in the universe. Yet, astronomers noticed a small number of stars (around 20 of these stars have been discovered till today) that move with a surprising high speed. Some of them move through the Milky Way with more than 1.8 million kilometers per hour.

These “hyper-speed stars” are so fast, and the gravity of our galaxy cannot stop them, so they’re expected to leave the Milky Way Galaxy in the future. “The hyper-speed stars are mainly found in the constellations of Leo and Sextant,” explained Boubert. “Explanations highlighting the speed of those stars are various, but no one had explained why the stars have fissured this part of the space,” he added.

Astronomers assume that they have been formed of the Great Magellan Cloud, a dwarf galaxy that orbits our Milky Way at a speed of 4.1 million kilometers per hour. There, the stars probably belonged to twin systems. When a partner explodes in such system, the other displaces from its orbit into space with a huge speed, as it was stroke by a slingshot. Despite that stars cannot reach the observed hyper velocities, they become sufficiently fast to escape the gravity of the Great Magellan Cloud.

When the stars displace out of the dwarf galaxy, this latter’s velocity is added to the speed of the star, just like a stone thrown in the direction of a moving train. The researchers used a special computer program to mimic the development of stars in the neighboring dwarf galaxy and pursued the flight paths of all the runways. “We think that around 10,000 runways are spread across the sky,” said Boubert. He also noted that during the simulation, half of those stars were fast enough to escape the Milky Way’s gravity, which as classifies them among the hyper-speed stars.

Yet, most of the wild stars have exploded during their movement, and left a neutron star or a black hole. Therefore, researchers suppose that along with those ten thousand stars, over half million neutron stars and black holes fled the Great Magellan Cloud and flied rapidly through the Milky Way Galaxy.