Astronomers discover a new type of star covered in helium burning ashes
A team of German astronomers, led by Professor Klaus Werner of the University of Tübingen, have discovered a strange new type of star covered in the by-product of helium burning. It is possible that the stars might have been formed by a rare stellar merger event.
Published alongside the work of Professor Werner and his team, a second paper from a group of astronomers from the University of La Plata and the Max Planck Institute for Astrophysics offers a possible explanation for their formation."We believe the stars discovered by our German colleagues might have formed in a very rare kind of stellar merger event between two white dwarf stars," says Dr Miller Bertolami of the Institute for Astrophysics of La Plata, lead author of the second paper.
Stellar mergers are known to happen between white dwarfs in close binary systems due to the shrinking of the orbit caused by the emission of gravitational waves.
Yet no current stellar evolutionary models can fully explain the newly discovered stars. The team need refined models in order to assess whether these mergers can actually happen. These models could not only help the team to better understand these stars, but could also provide a deeper insight into the late evolution of binary systems and how their stars exchange mass as they evolve.
"Normally we expect stars with these surface compositions to have already finished burning helium in their cores, and to be on their way to becoming white dwarfs. These new stars are a severe challenge to our understanding of stellar evolution." explains Professor Werner.