


Newly-discovered ‘hypervelocity stars’ flee our galaxy

The Milky Way at 5,000 meters.
(Serge Brunier / nasa.gov)



Palladino works under the supervision of Kelly Holley-Bockelmann, assistant professor of astronomy at Vanderbilt University, who said that the phenomenon of stars fleeing the galaxy is very rare.



The discovery of this new set of “hypervelocity” stars was described at the annual meeting of the American Astronomical Society in Washington DC. It was also published in the Jan-1 issue of the Astrophysical Journal. Australian, Spanish and Mexican specialists also contributed to the study.

It should be noted that the Milky Way’s central black hole has a mass equivalent to four million suns, which produce a gravitational force strong enough to accelerate stars to hyper velocities.

Image of hypervelocity star shown in red on the galaxy views. (Sloan Digital Sky Survey)

The previously described effect involved binary pairs of stars that get caught in the black hole’s gravitational grip.

The pair is sucked in by the hole; while one of the stars spirals towards the core, the other one receives a huge kick and is thrown out of the galaxy.

18 giant blue hypervelocity stars have been found to have undergone this process.

They are called HVSs and were first described by Los Alamos National Laboratory scientist, Dr. Jack Hills, in 1988.

The hypervelocity stars’ existence was confirmed 17 years later, when Smithsonian astronomers found the first outcast star. Two more hypervelocity stars were found in 2006. In 2010, astronomers using NASA's Hubble Space Telescope reported detecting HE 0437-5439 - a hypervelocity star that had sped away from the galaxy at a speed of 2.5 million kilometers an hour.

Now, the latest study by Palladino and her colleagues has discovered 20 more stars that can be categorized as the new type of “hypervelocity stars.”

Palladino explained that the study was underpinned by highly precise calculations.


The mystery, however, remains: how do stars do that? The scientists say they are working to solve the conundrum.