(ORDO NEWS) — A team of German astronomers have discovered a new star of an unusual type, the surface of which is covered with helium combustion products. Perhaps such stars are formed as a result of rare collisions between stars.
While the surfaces of ordinary stars contain hydrogen and helium, the surfaces of stars discovered by a team led by Professor Klaus Werner of the University of Tübingen, Germany contain carbon and oxygen, the “ash” produced by the fusion of helium.
Such a composition is very exotic for a star. The situation becomes even more confusing because these new stars have temperatures and sizes that indicate that helium-burning processes still occur in the cores of these stars, a property that is usually more characteristic of more mature stars than those that Werner and his group watched.
Published next to Werner’s work, a second scientific paper by a team led by Dr. Miller Bertolami of the Institute of Astrophysics in La Plata, Spain, proposes a possible explanation for the formation of this star.
“We believe that the stars discovered by our German colleagues could have formed as a result of a rare type of stellar collision between two white dwarfs,” Bertolami said. White dwarfs are the remnants of larger stars that have used up their stellar fuel, shrank in size, and become much denser.
Collisions usually occur between white dwarfs in a close binary due to orbital contraction caused by gravitational wave emission.
“Normally, mergers between white dwarfs do not lead to the formation of stars enriched in carbon and oxygen,” Miller explained.
“But we believe that in the case of binary systems formed from components with strictly defined masses, a carbon- and oxygen-rich white dwarf can be torn apart and end up on the surface of a helium-rich star – which leads to the formation of such stars.”
Currently, the models of stellar evolution available to scientists cannot fully explain the formation of these newly discovered stars.
The team needs refined models to assess how likely such collisions are. Until more detailed models of the evolution of binary stars are developed, the origin of these helium-burnt stars will remain a matter of debate.
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