Mystery of Hypervelocity Stars Revealed

Astronomers have always wondered what is the origin of the rare hypervelocity stars. These cosmic bodies are super suns which travel all over the Milky Way at incredible speeds which extend up to 500 kilometers per second. A new study recently published in the journal Monthly Notices of the Royal Astronomical Society shows an interesting new perspective on their origin.

Researchers disprove the former theory on the origin of hypervelocity stars

Until now, researchers succeeded to identify only 20 hypervelocity stars. Regarding their origin, they thought that a supermassive black hole was responsible with pushing them away from their orbits. This black hole was supposedly placed at the heart of the galaxy.

Now, a team of researchers from the University of Cambridge looked at data collected by the Sloan Digital Sky Survey. What they found proved this former theory wrong. They discovered the hypervelocity stars were not expelled from the center of the Milky Way, but originate from a whole different galaxy, namely the Large Magellanic Cloud (LMC).

How do these stars reach out of their galaxy?

Most of these hypervelocity stars have been observed shining in the sky above the northern hemisphere, more precisely in the Sextans and Leo constellations. They dismissed the black hole hypothesis, and that’s how they found out their trajectories indicated a point outside of the Milky Way.

Therefore, they came up with the following explanation. A hypervelocity star can result from a binary star system. It originates as one half of this system and, when the other half explodes and turns into a supernova, our star is propelled far away and acquires such high speed. The force of the supernova would be so strong that the star escapes the gravitational pull of its galaxy and goes beyond its boundaries.

The name of the Large Magellanic Cloud is misleading, since it is in fact a small galaxy which orbits our Milky Way. Its physics would allow perfectly for stars to be slingshot out of it and reach a neighboring galaxy. Therefore, this was the perfect candidate for the place of origin of the hypervelocity stars.
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