The hyper-velocity white dwarf D6-2
Date: 17 May 2019
Copyright: ESA/Gaia/DPAC
The motion across the sky of hyper-velocity white dwarf D6-2, based on data from the second release of ESA's Gaia satellite.
The first half of the video shows how the star will move from its current position into the future, during the next 95 000 years, calculated from its true velocity across the sky, or proper motion, measured by Gaia. The second half of the video shows how the star has reached its current position over the past 95 000 years. The circle identifies the location of the supernova remnant G70.0-21.5, a likely progenitor of this high-speed star. For the sake of illustration, the motion is exaggerated by a factor of 300 billion.
This star was identified in a study by Ken Shen and colleagues, who exploited Gaia's information not only on the position and distance of stars but also on their velocities across the Milky Way to find three white dwarfs that are zipping through our Galaxy at very high speeds. One possible interpretation sees these hyper-velocity white dwarfs as the survivors of a particular type of thermonuclear explosion, known as a type-Ia supernova. These explosions happen when a white dwarf pulls matter from a stellar companion in a binary system; in this particular case, the astronomers believe that the explosion happened in a system of two white dwarfs, causing one of the two stellar remnants to disappear and throwing the other away at speeds over 1000 kilometres per second. Gaia data on the motion of one of these speedy white dwarfs even hints at the existence of a supernova remnant.
More information: Shedding light on white dwarfs – the future of stars like our Sun
Acknowledgement: Gaia Sky; S. Jordan / T. Sagristà, Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Germany