How the speed demons of the universe tell us something about the Milky Way

The fastest stars in the Milky Way are hurtling at more than a thousand kilometers per second. Ph.D. Candidate Fraser Evans has researched these elusive hypervelocity stars and discovered that they have a lot to teach us about black holes and supernovae, for example.

Hypervelocity stars (HVS) are stars moving so fast that they can escape the Milky Way’s gravity. in 2019, Astronomy scientists Discover a star – S5-HVS1 – that covers a staggering 1,755 kilometers per second. Dozens of such stars have been found since then. But there are probably about a thousand of them within our galaxy.

Millions of fake stars

Evans used computer simulations to turn out millions of fake images High speed stars through the Milky Way. He wanted to get a better understanding of where they were coming from and their speed.

To make it right Computer simulationWe used a lot of data from the Gaia space telescope, which has wonderfully mapped two billion stars in our Milky Way,” says Evans. The results of his research will make it easier to find hypervelocity stars in the future.

Black holes and supernovae

But why is it so important for astronomers to find out more about these speed demons? “We can assume with a great deal of certainty that some of the hypervelocity stars now detected were ejected after a gravitational encounter with the supermassive black hole at the center of the Milky Way: Sagittarius A*. We see a similar effect in the large star Magellanic Cloud, a galaxy ​Others that we believe also contain a black hole. In the right conditions, supernovae — exploding stars — can also spew out hypervelocity stars.

“Stars that become supernovae are incredibly rare in our Milky Way and the event is so short-lived that it is difficult to measure. Besides, there are so many stars and so much dust flying around Sagittarius A* that we can’t properly see what is going on there.” Evans explains. “Some hypervelocity stars fly in much clearer parts of space and can tell us more about where they come from. For example, about attraction black holes Or the amount of energy produced by the supernova.

Although Evans had no particular ambition to become an astronomer as a child, his studies and research made him fascinated by the ultrafast stars.

“It’s amazing stuff. A thousand kilometers per second is very fast. You can fly around the world in less than a minute. They also have a story to tell about processes in the universe that we know so little about and still have so much to discover.”