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Meet the 'zombie star' that survived a supernova blast
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‘Zombie star’: A 2005 image shows the spiral galaxy NGC 1309, the location of a supernova that did not result in stellar death. (Reuters/Handout/NASA, ESA, The Hubble Heritage Team and A. Riess)
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stronomers have observed a star in a relatively nearby galaxy that not only survived what ordinarily should have been certain death, a stellar explosion called a supernova, but emerged from it brighter than before the blast.
Meet the "zombie star”.
The star at issue, observed with the Hubble Space Telescope, is known as a white dwarf, an incredibly dense object with about the mass of the Sun crammed into the size of Earth. A white dwarf is the remaining core of a star that blew off a lot of its material at the end of its life cycle, as our Sun is expected to do about 5 billion years from now.
This white dwarf is gravitationally locked in orbit with another star in a pairing called a binary system, with its strong gravitational pull siphoned off and incorporating a good deal of material from this unfortunate companion. That is where the trouble started.
In doing so, the white dwarf reached a mass threshold of around 1.4 times that of the Sun that caused thermonuclear reactions in its core that made it detonate in a supernova, an event that should have killed it.
"We were quite surprised that the star itself had not been destroyed, but had actually survived and is brighter than before it exploded," said Curtis McCully, a senior astrodata scientist at Las Cumbres Observatory in California and lead author of the research published this month in the Astrophysical Journal.
"During the explosion, radioactive material was produced. This is what powers the brightness of the supernova. Some of this material was left over in the surviving remnant star and acted as fuel to heat the remnant," McCully added.
