Breathe deeper: astronomers have found a white dwarf with an atmosphere of pure oxygen

Astronomers from the Brazilian State University of Rio Grande do Sul, while studying the data collected by the Sloan Digital Celestial Survey program over the past 15 years, came across a unique celestial object . In the white dwarf SDSSJ124043.01 + 671034.68, which they nicknamed Dox ([diox]), they found, the atmosphere is 99.9% pure oxygen.

Scientists have never seen anything like it before. White dwarfs are the final stage of the evolution of almost all stars (except the largest). When a star drops its envelope and forms a planetary nebula, in its place remains a core with a mass comparable to that of the Sun, but at the same time 100 times smaller. The luminosity of white dwarfs is extremely low, and therefore it is quite difficult to detect them - but, according to some estimates, they make up from 3 to 10% of the stellar population of our galaxy.

The atmosphere of typical stars is almost 90% hydrogen, almost 10% helium, and contains traces of heavier elements. Some scientists believe that the composition of heavy elements in the atmosphere of a star is consistent with their composition in the rocky planets of its system. And even when the star drops the envelope, the atmosphere remaining in the white dwarf has a similar composition. Hydrogen and helium, as the lightest elements, “float up” and remain in the atmosphere. What process led Dox to complete loss of light elements remains unclear.
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“This white dwarf came as a complete surprise,” says astronomer Kepler de Souza Oliveira, the head of research . “And since we didn’t expect to find something like this, finding it was an even more difficult task.”

The size of the Dox is slightly larger than the Earth, while its mass is 60% of the solar. In addition to oxygen, there are traces of neon, magnesium and silicon in its atmosphere. The unique composition of the atmosphere suggests that this object appeared as a result of some rare process.

Another mystery of Dox is the fact that it clearly originated from a small star — and in such a star such heavy elements as oxygen are not synthesized. By all the rules, Dox would have to weigh at least twice as much in order to be able to synthesize this element. And then in the atmosphere of a dwarf one could meet his tracks - but still, the atmosphere is not entirely composed of him.

Kepler believes that the solution to Dox may lie in the possibility of its formation in the place of a double star system. He argues that although it is customary in astrophysics to study and calculate the parameters of the evolution of single stars, about 30% of all stars interact in any way with their companion in binary stellar systems.

A possible development of events was a double star system, made of a white dwarf and a red giant. At some point, the giant expanded so that Dox began to drag gas out of its atmosphere. And then the giant exploded and all the light elements that were in the atmosphere evaporated, leaving only oxygen. Similar scenarios have already been described by scientists - except that they have never led to the fact that the star has only oxygen in the atmosphere.