Astronomers have discovered a new type of “freak star” covered in helium-burning ashes, which is believed to have formed by a rare stellar merger event.
A German team of experts were looking for “hot stars” in Arizona using a Large Binocular Telescope when they came across two stars with unusual properties. The stars are known as PG1654+322 and PG1528+025, and are about 10,000 and 25,000 light years away from Earth within our galaxy.
The experts reported “while normal star surfaces are composed of hydrogen and helium, these newly-found stars are covered in great quantities of carbon and oxygen – the by-product of helium nuclear fusion. Astonishingly high abundances of both carbon and oxygen – each accounting for around 20 percent of surface composition for both stars.”
“Stars that are covered in this much carbon and oxygen usually have finished nuclear fusion reactions that take place at their core. However, temperatures and diameters of the two newly-discovered stars indicate that helium nuclei continue to fuse inside them – an unprecedented finding,” the experts reported.
The research was conducted by a team of astronomers, led by Professor Klaus Werner of the University of Tübingen, and published in Monthly Notices of the Royal Astronomical Society.
“We normally expect stars with the chemical surface composition of the stars discovered to have completed the helium fusion in their centers and to be in the final stages of becoming white dwarfs,” said Professor Werner.
“These new stars are a severe challenge to our understanding of stellar evolution. Carbon and oxygen are normal in old stars that are fusing helium, but only in their cores. So it is extremely unusual to see them in large quantities at their surface.”
“We believe that the stars discovered by our German colleagues were formed by a very rare type of merging between two white dwarfs,”said Miller Bertolami, author of a second companion paper by astronomers, also published in Monthly Notices of the Royal Astronomical Society.
“White dwarfs are the remnants of larger stars that have exhausted their nuclear fuel, and are typically very small and dense,” he explained.
There are currently no stellar evolutionary models that can fully explain how exactly these new stars were formed and why, which could create a whole new binary for scientists to work off of when it comes to new star discoveries.
The two stars will continue to be monitored as a part of the larger-scale research the team is doing to track down short-lived, hot stars. This research should also help the team better understand what exactly these stars endured in order to evolve into what they are currently.
Eric Mastrota is a Contributing Editor at The National Digest based in New York. A graduate of SUNY New Paltz, he reports on world news, culture, and lifestyle. You can reach him at firstname.lastname@example.org.