Astronomers have discovered the fastest escaping star ever observed within the Milky Way Galaxy. It is moving at an incredible speed resulting from a massive explosion. The white dwarf star named J0927 is racing through space at 8,226,967 km/h. It is referred to as a super-speed star because its velocity will eventually allow it to completely escape the gravitational pull of the Milky Way. J0927 is flying alongside three other fast-moving stars, believed to be the aftermath of a Type Ia supernova, one of the most powerful explosions in the universe. The research team, led by Kareem El-Badry at the Harvard-Smithsonian Center for Astrophysics, announced the discovery on the arXiv data repository, as reported by Live Science on June 15th.
Simulated white dwarf being ejected from a Type Ia supernova. (Image: Mark Garlick/Science Photo Library).
A Type Ia supernova occurs when two stars orbit each other in a circular pattern, with one of them being a white dwarf. The process involves the white dwarf siphoning off hydrogen from the companion star, leading to a nuclear fusion reaction that triggers an extremely powerful nuclear detonation. However, a simple stellar explosion is not sufficient to propel a star at such high speeds. Astronomers suspect that the ejected super-speed star is a result of a specific form of Type Ia supernova called a D6 supernova.
In a D6 supernova, two white dwarf stars orbit each other, with one star stripping off the remaining helium layer on the surface of the companion star. This process releases a significant amount of energy on the surface of the white dwarf, causing it to “eat” its companion star to the point of reactivating a nuclear fusion reaction in its core, leading to a stellar explosion.
Despite the existence of such powerful Type Ia supernova events, evidence of them and the expelled white dwarfs remains elusive. To search for potential candidates, El-Badry and colleagues examined the Gaia stellar catalog, a project aiming to create the most detailed map of the Milky Way Galaxy. From Gaia data, the research team discovered white dwarf stars. By carefully analyzing their chemical composition (primarily oxygen and carbon), they confirmed that the escaping white dwarfs are the result of an explosion that caused the loss of helium and hydrogen.
Measurements of the white dwarfs revealed that J0927 is the fastest escaping white dwarf ever observed within the Milky Way Galaxy, surpassing the previous record held by star D6-1 at 7,919,904 km/h. The research team estimates that D6 supernovae may account for half of all Type Ia supernovae. However, to confirm this, they will need to find more runaway stars racing through space.