Foreign media reported that the sun was moving through space at 720,000 km/h – but it was a leisurely “Sunday stroll” compared to some stars. Astronomers have now discovered a star called S5-HVS1 that travels at a staggering 6 million kilometers per hour (3.7 million miles per hour). Not only does this make it the fastest known star, but it’s enough to “throw” it out of the Milky Way.
Fast-moving stars are known as super-fast stars, and so far only a handful of such stars have been identified. Even so, “super-fast” stars are often defined as stars that travel at speeds of 500 kilometers per second, enough to escape the gravitational pull of the Milky Way and fly into interstellar space.
The S5-HVS1 is the fastest of these. It moves at a speed of more than 1,700 km/s – far more than the previous record holder, a white dwarf called US708, traveling at 1,200 km/s.
But where did these stars come from, and how fast did they come from? The most commonly accepted assumption is that the so-called Hills Mechanism – basically, when a binary system star hovers too close to a black hole, one is captured by a black hole and the other is ejected at high speed.
For S5-HVS1, the team was able to trace its journey and determine which black hole might be responsible. The black hole, known as The Sagittarius A, is a supermassive black hole at the center of the Milky Way.
Sergey Koposov, lead author of the study, said: “This is really exciting because we have long suspected that black holes will ‘extrefer’ stars at a high rate. But we have never explicitly linked a star so fast to the center of the Milky Way. We think the black hole ‘excited’ the star at a speed of thousands of kilometers per second about 5 million years ago. This ‘expulsion’ occurred when the ancestors of man kindhaded the first to learn to walk on two feet. “
The star, located in the constellation of Tashim, is part of the Southern Stellar Flow Spectrum Survey (S5) conducted by astronomers using the Anglo-Australian Telescope (AAT). Astronomers then used data from the Gaia satellite’s extensive list of stars to determine its speed and trajectory.
The study was published in the Monthly Journal of the Royal Astronomical Society.