Meet the ‘zombie star’ that survived a supernova blast
WASHINGTON: Astronomers have observed in a relatively nearby galaxy a star 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 a kind 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 - a pairing called a
binary system - and with its strong gravitational pull siphoned off and incorporated 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 - about 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 California-based Las Cumbres Observatory, 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.
This white dwarf resides in a spiral galaxy called NGC 1309, about three quarters the size of our Milky Way. Like the Milky Way, NGC 1309 resembles a spinning pinwheel when viewed from above or below. The white dwarf is located 108 million light years from Earth. A light year is the distance light travels in a year - 9.5 trillion km.