A team of astronomers at Harvard University has discovered a hypervelocity star cluster, which includes a record-breaking star traveling at a speed of 8,226,967 km/h.
The astronomers found the fastest runaway star ever observed in the Milky Way. It is hurtling through space at an incredible speed following a massive explosion. The white dwarf star named J0927 is racing through the cosmos at 8,226,967 km/h. Referred to as a hypervelocity star, its speed is sufficient for it to eventually escape the gravitational pull of the Milky Way. J0927 is traveling alongside three other fast-moving stars, believed to be the result of a Type Ia supernova, one of the most violent explosions in the universe. The research team, led by Kareem El-Badry at the Harvard-Smithsonian Center for Astrophysics, announced the discovery on the data platform arXiv, as reported by Live Science on June 15.
Simulation of a white dwarf being ejected from a supernova explosion. (Image: Mark Garlick/Science Photo Library).
A Type Ia supernova occurs when two stars orbit each other, one of which is a white dwarf. This process allows the white dwarf to siphon off hydrogen from its companion star, triggering a reaction that leads to a tremendous thermonuclear explosion. However, a simple stellar explosion is not sufficient to propel a star at such high speeds. Astronomers suspect that the hypervelocity star was ejected due to a special type of Type Ia supernova known as Type D6 supernova.
In a Type D6 supernova, two white dwarfs orbit each other, with one star stripping away the remaining helium layer from the surface of its companion star. This process generates significant energy on the surface of the “cannibal” white dwarf, reactivating thermonuclear reactions and driving shockwaves deep into the core, resulting in an explosion.
Despite the prevalence of such powerful supernova explosions, evidence of them and the ejected white dwarfs remains elusive. To find potential candidates, El-Badry and his colleagues examined the Gaia star catalog, a project aimed at creating the most detailed star map of the Milky Way. Using Gaia data, the research team identified white dwarfs. Through a closer examination of their chemical composition (primarily oxygen and carbon), they confirmed that the runaway white dwarf was the result of an explosion that stripped it of helium and hydrogen.
Measurements of the white dwarf revealed that J0927 is the fastest runaway white dwarf ever observed in the Milky Way, surpassing the previous record of 7,919,904 km/h held by star D6-1. The research team estimates that Type D6 supernovae could account for half of Type Ia supernovae. However, to confirm this, they will need to find more runaway stars traversing through space.
