White dwarf survives supernova explosion and becomes brighter than before

(ORDO NEWS) — A small star “reborn” after a cosmic catastrophe and even increased its brilliance – scientists compare it to Obi-Wan Kenobi, who made a similar rebirth after his death in the Star Wars universe.

A white dwarf in a distant galaxy survived an underpowered supernova explosion in 2012, and new observations have shown that it even brightened up as a result of the catastrophe.

Supernovae are the explosions of stars that experience a catastrophic death. So, for example, a white dwarf can die, located in a close binary system with a larger star – for example, a red giant. Gradually pulling matter from the “loose” neighbor, it eventually ignites with a thermonuclear explosion and disperses throughout space.

However, in supernovae of the Iax subclass, this process fails: their flashes are not so bright, and the white dwarf can survive the explosion, ejected into space at high speed. Such a “zombie” star that survived a supernova was discovered by scientists in the southern constellation Eridanus.

Spiral galaxy NGC 1309 is located more than a hundred million light-years away. In January 2012, an Iax-type supernova was detected in it.

Later, astronomers studied archival images of the Hubble space telescope, which had repeatedly observed a distant galaxy, and were able to identify the precursor star of the supernova SN 2012Z. However, in the images taken after the explosion, they were in for a surprise: the white dwarf survived.

White dwarf survives supernova explosion and becomes brighter than before 2
On the left is a general view of the galaxy NGC 1309, on the right are images of the vicinity of SN 2012Z before, during and after the outburst

Until now, scientists have not known a single reliable example of such a star. Their existence was predicted by models, and the white dwarf LP 40-365, whose fast and lonely motion is best explained by a supernova , has been studied.

For SN 2012Z, the line from the progenitor star to the supernova and then to the surviving dwarf was traced in its entirety several years ago. Now, however, astronomers have noticed a new oddity in this system. After the explosion, the white dwarf became even brighter than it was before it.

Curtis McCully and his colleagues attribute this to the weakness of the Iax supernova. It was not enough not only to destroy the white dwarf, but also to throw out all the matter of the neighboring star that had accumulated in the vicinity.

After the explosion, part of it fell on the surviving dwarf, increasing its brilliance. In this case, the increase in brightness is temporary, and in the future the dwarf will return to its normal state, only becoming even more loose and dimmer.

“The surviving star is a bit like Obi-Wan Kenobi, who was resurrected as a ‘spirit of power’ in Star Wars,” says Andy Howell, one of the authors of the new work. “Nature tried to destroy this star, but it came back even stronger than you could imagine. It is still the same star, but in a new form. She has transcended death.”

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