Exotic white dwarf J124043, the speed of which reaches 900 thousand kilometers per hour, maybe the result of a supernova explosion of a type not yet known.
The white dwarf, having survived the “partial” supernova explosion, has received a tremendous momentum and is moving along the Milky Way at a speed of about 900 thousand kilometers per hour. Its flight and a very unusual composition can indicate a new type of supernovae that were previously unnoticed by astronomers – and that other “high-speed” white dwarfs can be found in the Galaxy and beyond. This is stated in an article published in the journal Monthly Notices of the Royal Astronomical Society.
Boris Gänsicke and his colleagues at the University of Warwick investigated the white dwarf SDSS J124043.01 + 671034.68, the strange chemical composition of which has puzzled scientists for more than a year. Such objects are considered the remains of large red giants – in fact, their cores, preserved after the dumping of the outer shells. As a rule, the atmosphere of white dwarfs is composed of hydrogen and helium, with only small impurities of elements such as oxygen and carbon.
However, neither hydrogen nor helium was found on J124043: its atmosphere turned out to be oxygen, with some amounts of other elements, including neon, sodium, magnesium, silicon, aluminum – the products of a supernova explosion. In fact, white dwarfs are quite massive and dense, and entering a binary system with an ordinary, more “friable” star, they can pull part of its substance. Gradually, this increases the mass of the dwarf, again starting thermonuclear reactions in it.
It is believed that all this culminates in a Type Ia supernova explosion that scatters synthesized heavy elements through space. The fact that the white dwarf J124043 experienced something like this can be indicated by its small mass, which is only 40 percent of the sun: apparently, a significant part of the substance was lost to them. However, no iron, nor nickel or chromium, typical products of this process, was found in the atmosphere of J124043. But the speed of the white dwarf was an astounding 900 thousand kilometers per hour.
“This star is unique”, says Professor Gänsicke. – Its chemical composition, low mass, and high speed – all this indicates that it was part of a close binary system and survived the launch of thermonuclear reactions. Perhaps it was a type of supernova, but one that we have not seen before. ” Scientists suggest that the white dwarf could develop along the path of the usual supernova Ia, but at some point it dramatically dropped a significant part of its mass, further spinning the binary system.
As a result, gravity and centrifugal forces worked like a sling, launching the J124043 in flight. Thermonuclear reactions with the formation of heavy elements of the iron group in it ceased, and the heavily “thinner” dwarf set off on a high-speed journey through the Galaxy. Astronomers suggest that such an unusual mechanism of an “unfinished” supernova may also act in some other binary systems. However, it should be especially difficult to notice such outbreaks, since they are very short-lived.