A unique ultra-massive white dwarf star could be key to understanding the structure of the universe, scientists have announced. The star has “unusually high” levels of carbon in its atmosphere.
This cannot be explained through the normal process of a star’s evolution, according to a new study.
The star instead appears to have formed when two white dwarfs merged into each other approximately 1.3 billion years ago.
The white dwarf failed to explode as a supernova, as would normally be expected.
Scientists believe the star, slightly larger than the Sun, could help experts understand how stars merge.
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This marks the first time astronomers have identified a merged white dwarf by using its atmosphere as a clue.
Dr Mark Hollands, from the University of Warwick’s department of physics, and lead author of the study, said: “We have a composition that we can’t explain through normal stellar evolution.
“The only way you can explain it is if it was formed through a merger of two white dwarfs.”
White dwarfs are the remnants of stars that have burnt out all their fuel and shed their outer layers.
The astronomers found this one to have 1.14 solar masses, despite being only about two-thirds the size of the Earth.
Based on its orbit around the Milky Way, astronomers believe the star is older than it looks.
The white dwarf’s age is hard to understand as the merger restarted the cooling process usually used to estimate its age.
Although the merging likely occurred about 1.3 billion years ago, the individual stars could have existed for many billions of years prior.
Dr Hollands added: “Maybe the most exciting aspect of this star is that it must have just about failed to explode as a supernova – these gargantuan explosions are really important in mapping the structure of the Universe, as they can be detected out to very large distances.
“However, there remains much uncertainty about what kind of stellar systems make it to the supernova stage.
“Strange as it may sound, measuring the properties of this ‘failed’ supernova, and future lookalikes, is telling us a lot about the pathways to thermonuclear self-annihilation.”