From the rare two -star collision was born an Earth’s size star -size

Astronomers have obtained convincing evidence that a nearby white dwarf is, in fact, the remnant of the two -star fusion – a rare star discovery revealed through ultraviolet observations by the Hubble space telescope of carbon in the star’s warm atmosphere.

As white dwarfs They are the dense nuclei left behind when the stars run out of their fuel and collapse.

They are star embers The size of the earth, typically half of the sun mass, consisting of carbon oxygen cores with surface layers of helium and hydrogen.

Although white dwarfs are common in the universe, those that have an exceptionally high mass (more than the sun) They are rare and enigmatic.

In a scientific published in the magazine Nature AstronomyWarwick University astronomers report their investigations into a white-known white dwarf, located 130 light years away, which was designated WD 0525+526.

With one Mass 20% higher than our sunWD 0525+526 is considered “ultrasound” and the way this star formed is not fully understood.

Such a white dwarf could form from the collapse of a massive star. However, ultraviolet data from the hubble space telescope revealed that WD 0525+526 has small amounts of carbon to climb from its core to its atmosphere rich in hydrogen – suggesting that this white dwarf has not originated in a single mass star.

“In the optical light (the type of light we see with our eyes), WD 0525+526 looks like a heavy white dwarf, but normal,” he says Sneharata sahuresearcher at Warwick University and first author of the study.

“However, through ultraviolet observations obtained with Hubble, we were able to detect weak carbon signatures that were not visible to optical telescopes, ”he adds.

“Finding small amounts of carbon in its atmosphere is a revealing sign that this massive dwarf is probably the remnant of a fusion between two stars that collided“, I note Sahu.

“It also tells us that There may be many more remnants of mergers like this, masked white dwarfs with pure hydrogen atmosphere. Only the remarks in the ultraviolet would be able to reveal them, ”he concludes.

Normally, Hydrogen and Helium They form a thick barrier around the nucleus of a white dwarf, keeping elements such as carbon hidden. In a fusion of two stars, the hydrogen and helium layers can burn almost completely as the stars combine.

The resulting singular star has a very thin wrapping that no longer prevents carbon from reaching the surface – This is exactly what in WD 0525+526.

“We measure that the hydrogen and helium layers are ten billion times thinner than in typical white dwells. We think these layers have been removed during the merger, and this is what the carbon now appears to appear on the surface,” he says Antoine Bédardco -author of the article.

“But this remnant It is also unusual: It is about 100,000 times less carbon to the surface than other remnants of the merger, ”adds the researcher.

”The low carbon level, along with the high star temperature (almost four times warmer than the sun), tells us that WD 0525+526 is much further in advance in its post-fusion evolution than previously found, ”details Bédard.

“This discovery helps us better understand the fate of binary star systems, which is critical to related phenomena, such as supernova explosions,” he concludes.

To add to the mystery It is the way carbon hits the surface in this much warmer star.

The other remaining stars of mergers are in a more advanced phase of their evolution and They are cold enough so that convection bring carbon to the surface. But WD 0525+526 is too hot for this process.

Instead, the team identified a more subtle way of mixture called semi -economic, seen here for the first time in a white dwarf. This process allows Small amounts of carbon rise slowly for the star’s rich atmosphere of the star.

“Finding clear evidence of mergers in individual white dwarfs is rare,” he adds Boris GänsickeProfessor at the Department of Physics at Warwick University, who obtained Hubble data for this study.

“But ultraviolet conceoscopy gives us the ability to detect these signs early, when carbon is still invisible to optical wavelengths. As the earth’s atmosphere blocks ultraviolet light, these observations have to be made from space and today, today, Only the hubble You can do this work, ”details Gänsicke.

“Hubble has just turned 35 and, while still working well, it is very important that we begin to plan a new space telescope that will replace it,” says the astrophysicist.

As WD 0525+526 continues to evolve and cool, it is expected that over time more carbon will emerge at its surface. For now, its ultraviolet glow offers A rare glimpse of the initial phase of the aftermath of a star fusion – and a new reference on how binary stars end their lives.