Milky Way

Scientists Have Discovered a Hypervelocity Star Heading Out Of The Milky Way

A star has been seen making its way out of the Milky Way at a speed of 3.7 million miles per hour, the equivalent of 1056 miles per second or ten times faster than the majority of the stars in the Milky Way, including the sun. However it is widely believed it will take a further 100 million years before it actually makes its way out of the Milky Way and will then spend eternity roaming around intergalactic space.

Hypervelocity stars were discovered by astronomers in 2005 although numbers are still low, with fewer than 30 found in the last 14 years. Named S5-HVS1, the star has made its way to the constellation of Grus, which is at a distance of just over 29,000 light-years.

University of Oxford astronomer Dr. Douglas Boubert confirmed that the S5-HVS1’s velocity is so high it will ‘inevitably leave the Galaxy and never return,’ while Carnegie Mellon University researcher Dr. Sergey Koposov exclaimed ‘this is super exciting, as we have long suspected that black holes can eject stars with very high velocities’.

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It is the first time a black hole has thrown a star out of the galaxy since the act was predicted 30 years ago via the Hills mechanism suggested by astronomer Jack Hills, and Dr. Ting Li from Carnegie Observatories and Princeton University was quick to confirm that ‘seeing this star really is amazing as we know it must have formed in the galactic center, a place very different to our local environment.’

The Southern Stellar Stream Spectroscopic Survey (S5) are responsible for the discovery thanks to the data collected from a 3.9-m Anglo-Australian Telescope alongside ESA’s Gaia satellite. The astronomers were then able to understand the star’s journey out of the Milky Way’s center.

S5’s main goal scientifically is to probe the stellar streams, however they were able to provide some of their resources to look around the Milky Way to see if there was anything interesting. Using this technique they were able to discover the star and Lowell Observatory’s Dr. Kyler Kuehn is hopeful they will ‘find even more’.

The team’s paper was published in the Monthly Notices of the Royal Astronomical Society.