Artist's impression of the Gaia spacecraft, with the Milky Way in the background

Data from the Gaia spacecraft (artist’s rendering) helped to identify stars that survived a runaway nuclear reaction in their cores. Credit: ESA/ATG/ESO/S.Brunier

Astronomy and astrophysics

Three zombie stars on the run

Stars moving at high velocity seem to have managed to live on after cataclysm.

Astronomers have discovered three peculiar runaway stars that have apparently survived cataclysmic explosions at their cores.

A white dwarf is an ageing star that has burned through its original fuel. Under certain conditions, a white dwarf’s burnt-out core re-ignites; the core’s subsequent explosion is known as a supernova. Some stars are thought to survive these explosions to become so-called zombie stars.

To find potential zombies, Roberto Raddi at Friedrich Alexander University Erlangen–Nuremberg in Bamberg, Germany, and his colleagues searched for high-velocity objects that could have been propelled by explosions. The team mined data from sources including the European Space Agency's Gaia space telescope.

The researchers identified three stars that have unusually low masses for white dwarfs and atmospheres that are made mostly of neon and oxygen. These traits are markers of a relatively weak explosion that failed to blow its star completely to smithereens.

The authors propose that these three stars — along with a similar star found in 2017 — are the first known members of a new class of star.