Runaway Stars Help Astronomers Trace Dark Matter Distribution Across the Milky Way Galaxy

Astronomers have had their sights set on fast-moving runaway stars as a potent new means to probe the hidden structure of the Milky Way. These rare objects, called hypervelocity stars, travel so rapidly that they can escape the galaxy's gravity. Tracking the motion of those stars, scientists can then learn more about how mass is distributed through the Milky Way and around its invisible dark matter. A new large-scale search has now identified dozens of such stars, offering fresh insight into the galaxy's gravitational pull and its vast outer halo.

RR Lyrae Stars Help Trace Origins of Hypervelocity Stars Ejected from the Milky Way's Core

According to a report published in The Astrophysical Journal, the study was performed by astronomers from scientific institutes in Beijing, led by Haozhu Fu of Peking University, on the RR Lyrae stars. Those stars pulse in an orderly manner, so their distances can be measured simply with the help of data from the Sloan Digital Sky Survey and the Gaia space telescope.

Hypervelocity stars travel faster than 1,000 km/s and are ejected by encounters involving Sagittarius A* in the galactic centre – one star is stripped while its companion is captured.

87 Hypervelocity RR Lyrae Stars Offer New Clues to the Milky Way's Gravity and Dark Matter Halo

The researchers started with over a lakh of RR Lyrae stars and scrutinised the data closely. This dropped the sample to 87 strong runaway star candidates, including some clustered around the galactic centre and others by the Magellanic Clouds.

By tracking these stars back to where they came from, scientists can map the gravitational field of the Milky Way. This helps to explain how dark matter spreads through the galaxy's halo and gets researchers a step closer to unravelling one of physics' greatest mysteries.