Fastest stars in the Milky Way are ‘runaways’ from another galaxy

A group of astronomers showed that the fastest stars in our galaxy – traveling so fast that they can escape the Milky Way – are actually fleeing a much smaller galaxy that orbits ours.

Researchers at the University of Cambridge used data from the Sloan Digital Sky Survey and computer simulations to show that these star spirals come from the Large Magellanic Cloud (LMC), a dwarf galaxy that orbits the Milky Way.

These fast-moving stars, known for hypervelophiles stars, were able to escape from their place of origin when the explosion of a star in a binary system caused the other to fly with such a speed that it was able to escape the gravity of the CML And be absorbed in the Milky Way.

The results are published in the Monthly Notices of the Royal Astronomical Society and will be presented today (5 July) at the National Astronomy Meeting in Hull.

Astronomers thought that first hyper-stars, which are large blue stars, were dislodged from the center of the Milky Way by a super-massive black hole. Other scenarios involving disintegrating dwarf galaxies or chaotic star clusters may also explain the speed of these stars, but the three mechanisms do not explain why they are only found in a certain part of the sky.

To date, we have observed about 20 hypervelophiles stars, especially in the northern hemisphere, although it is possible that there is much more that can be observed only in the southern hemisphere.
“Earlier explanations for the origin of hypervelocity stars are not satisfied,” said Douglas Boubert, a doctoral student at the Cambridge Institute of Astronomy and lead author of the article. “Hypervelocity stars are mainly found in the constellations of Leo and Sextant – we wonder why this is the case.”
Another explanation for the origin of hyper-fast stars is that they are fleeing from a binary system. In binary star systems, in addition to the two stars are nearby, the faster they are moving towards each other.

If a star explodes like a supernova, the binary star and the remaining flies can be divided at the speed of its orbit. The star escape is known as a fugitive. Fugitive stars in the Milky Way are not fast enough to hyper-speed because the blue stars can not rotate close enough and without the merging of the two stars. But a fast moving galaxy could give rise to these fast stars.

The CML is the largest and fastest dozen of the dwarf galaxies orbiting the Milky Way. It has only 10% of the mass of the Milky Way, and the fastest fugitives born in this dwarf galaxy can easily escape its gravity.

The LMC flies around the Milky Way at 400 kilometers per second, like a bullet fired from a moving train, the speed of these fugitive stars is the speed at which they were ejected more LMC speed. This is fast enough to be the stars of hypervelocity.

“These stars have only gone up an express train – no wonder they are fast,” said co-author Rob Izzard, a fellow Rutherford at the Astronomy Institute.

“This also explains their position in the sky, because the faster fugitives are expelled along the orbit of the CML to the constellations of Leo and Sextant.”

The researchers used a combination of Sloan Digital Sky Survey data and computer simulations to model how hypervelophiles stars could escape LMC and ending up in the Milky Way.

The researchers simulated the birth and death of stars in CML in the last two billion years, and noted every star in the race.

The orbit of the stars to escape after falling CML was followed by a second simulation that included the severity of the condition and the Milky Way. These simulations allow researchers to predict where in the sky, it is expected to find fugitive stars from CML.

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