Hypervelocity stars (HVS), the fastest of the bunch, are especially interesting because they have achieved relativistic speeds (a fraction of the speed of light). Astronomers have estimated that with the right kind of gravitational acceleration, hypervelocity stars can reach 1/10th to 1/3rd the speed of light – roughly 30,000 to 100,000 km/s.
“Rare” is certainly an apt description. According to previous estimates made by astrophysicists, there are likely to be just 1000 HVS in our galaxy (that’s 0.0000005 % of the galactic population). But given their speed and the vast distances they travel, tracking these stars and creating a database of their movements could tell us a great deal about a number of cosmic mysteries.
By tracking the movement of HVS, astrophysicists will be able to better constrain the shape of the Milky Way’s dark matter halo. In addition, they could tell us a great deal about the formation and evolution of the Milky Way itself, as HVS is believed to be the result of galactic mergers and other extreme gravitational forces (i.e. supermassive holes). Having more to study could therefore help astronomers create a history of past galactic mergers.
It has also been ventured that HVS could allow astrophysicists to accurately constrain the mass of our galaxy, something that remains unresolved. On top of all that, previous research has indicated that HVS can carry their planetary systems with them, which could be one of the ways that life is spread throughout the cosmos (intergalactic panspermia).