An international team of astronomers has discovered six previously unknown to science “fleeing” stars, two of which have broken the record for the fastest speed of all such objects in the history of observations. The study has been published on the arXiv preprints server, and Phys.org tells us briefly about it.
Runaway stars are stars that move at an abnormally high speed relative to the surrounding interstellar medium. Until recently, only ten such stars were known. Their trajectories and speed will allow them to leave our Milky Way galaxy someday.
The new study was conducted using data from the Gaia Space Telescope survey. As a result, the researchers were able to detect six more fleeing stars. Two of them, designated J0927 and J1235, broke the record for the highest radial velocity: it has them at 1694 km / s and 2285 km / s, respectively. That is, these two stars are now the fastest among similar objects.
The supernovae that produced these stars are of a special type known as “Type 1a”. As the authors of the paper write, they arise in binary stellar systems in which one white dwarf slowly absorbs the stellar material of its companion as the stars rotate around each other. When enough material passes from one star to the other, a powerful flare occurs.
At a critical mass, the growing star can no longer resist gravitational pressure and collapses into itself, leading to a powerful explosion. And the “detonation” can be double. In this scenario, a white dwarf attracts and absorbs helium from the shell of a neighboring star. This helium detonates first, causing a shock wave, which subsequently causes a second detonation, this time of the star’s carbon core.
In the double detonation scenario, the remains of the neighboring star are ejected into space at the same speed as it orbited its “now-deceased” companion. This process allows the fugitive star to gradually reach an incredible speed as it moves through the Milky Way and eventually escape beyond its limits.
The new record-breaking J0927 and J0927 are stuck in orbit, not on a “fleeing” trajectory. As the authors suggest, the stars that are closest to the black hole at the center of our galaxy can also move at such dizzying speeds.
This discovery provides new insights into the cosmic phenomena that lead to such unique stars. In addition, it deepens our knowledge of the processes occurring in the universe and may lead to new discoveries in the future.