The scientists have discovered a completely unique type of star - a white dwarf, which atmosphere or the outer layer consists almost entirely of oxygen. Material about the opening was published in Science magazine. For comparison, the Earth's atmosphere contains only 21% of oxygen, Popular Mechanics reports. The discovery belongs to a group of Barzilian astronomers led by Kepler de Souza Oliveira from the Federal University of Rio Grande do Sul. The star was named SDSSJ124043.01 + 671034.68, but for convenience, the astronomers nicknamed it Dox.
Dox – is the only white dwarf of the 32 thousand known, which atmosphere consists of 99.9% oxygen. "This white dwarf is incredibly surprising," - Kepler says. "We could not even imagine that it could exist. And because we had no idea anything like it could even exist, that made it all the more difficult to find," - he added. As Popular Mechanics clarifies, white dwarfs – are evolved stars deprived of its own thermonuclear fuel - hydrogen and helium, and characterized by ultra-high density. Dox slightly exceeds the size of Earth, but its mass is 60% of the mass of our Sun.
Uniqueness of Dox is that almost all other white dwarfs in the sky have an atmosphere thick with light elements like hydrogen and helium. These light elements are the final dregs of the star's elemental fusion fuel that survived the star's earlier life-cycle. Due to their weight they are in the outer layer of white dwarfs. What happened to all these elements in Dox’s atmosphere is unknown. Furthermore, traces of heavier elements, such as carbon or oxygen, are detected in the atmosphere of 20% white dwarfs, though scientists still have not seen white dwarfs with a single element atmosphere.
Perhaps most perplexing, when oxygen atoms are found, they're spied in far heavier white dwarfs. Smaller white dwarfs evolve from smaller stars, which don't fuse together atoms into oxygen as they collapse. By all calculations, Dox would have had to be roughly double its weight to have even forged oxygen atoms in its earlier life. "We don’t understand where this oxygen even came from," - Kepler says. In short, Dox completely defies our general, scientific understanding of how stars evolve and eventually form into white dwarfs.
Kepler proposes the following suggestion: At some point Dox may have been a larger white dwarf, locked in a twirling ballet with another star much like our own Sun. These two stars were about the same distance apart as the Sun and Venus are. As the second star turned into a red giant it expanded rapidly and it actually engulfed the white dwarf in its outermost layer of gas. Kepler believes Dox would have started siphoning off the red giant's gas onto itself. At some point during that siphoning process, when it reached a few million degrees, it exploded. That explosion threw all types of matter out. That's when Dox might have lost all its hydrogen and helium. According to the astronomer, this type of situation is known to have happened with other stars, although it's never been seen to leave just oxygen.