Speedy White Dwarf Fragment Might Have Survived A Partial Supernova

Astronomers have discovered a star like none seen before. They think it may be the remnant of an incomplete supernova explosion, something that would explain one mystery, but create enough new ones to keep them happily hunting for a long time.

LP 40-365 is a 15th magnitude star, making it far too faint to see with the naked eye, but much brighter than the vast majority of objects recorded in sky maps.

Catalogs of stars registered the fact that it appears to be traveling very rapidly compared to the rest of the galaxy, and interested by such speedster stars, Professor Lilia Ferrario of the Australian National University and some fellow astronomers decided to check it out.

What they found, Ferrario told IFLScience, was more fascinating than anyone expected. LP 40-365’s light spectrum clearly marks it as a white dwarf, but one smaller than any we have seen before – just 0.14 times the mass of the Sun.

White dwarfs are extremely compact stars, where gravitational collapse is prevented by the pressure exerted by a gas of degenerate electrons. A teaspoon of white dwarf material would weigh many tonnes on Earth,” Ferrario said in a statement.

White dwarfs are the remnants of medium to large stars that have run out of fuel. They are called dwarfs because they are very compact, but, even with all the material they have lost, their masses are close to that of the Sun.

LP 40-365 “must have interacted with something to end up the way it is,” Ferrario told IFLScience.

The explanation Ferrario and her colleagues have presented in Science is that LP 40-365 is the result of what is called a Iax supernova.

Type Ia supernovas are thought to occur when a white dwarf star that is part of a binary system with another star draws gas away from its companion until it has so much it explodes, although a subclass is triggered by the collision of two white dwarfs.

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