Astronomers Find Potential 'Zombie Star' SN 2012Z

Astronomers have found a star system that could have left behind a "zombie star."

The latest study shows that massive stellar explosions don't always destroy stars, but sometimes leave behind weird remnants that scientists have dubbed as zombie stars. The researchers used NASA's Hubble Space Telescope to locate the star system.

A supernova is an explosion of a massive star. These explosions usually wipe out the star. However, astronomers have now found a surprisingly weak explosion that has left behind a portion of a dwarf star.

The study is published in the journal Nature.

The researchers said that the study sheds light on a mysterious type of stellar event called Type Ia supernova, Space.com reported.

Type Ia supernovae (SNIa) are a result of the explosion of a carbon-oxygen white dwarf in a binary star system.

 "Astronomers have been searching for decades for the star systems that produce Type Ia supernova explosions," said scientist Saurabh Jha of the Rutgers University in Piscataway, New Jersey.

"Type Ia's are important because they're used to measure vast cosmic distances and the expansion of the Universe. But we have very few constraints on how any white dwarf explodes. The similarities between Type Iax's and normal Type Ia's make understanding Type Iax progenitors important, especially because no Type Ia progenitor has been conclusively identified. This discovery shows us one way that you can get a white dwarf explosion," Jha said in a news release.

The weak supernova is called SN 2012Z and is located in the galaxy NGC 1309, found 110 million light-years away from Earth. Hubble's Advanced Camera for Surveys began tracking the galaxy several years before the supernova explosion, which allowed astronomers to compare before and after images of the event.

According to the researchers, one possible explanation of the zombie SN 2012Z is that two stars in the binary star system pair were a mismatch. The more massive star in the system evolved quickly and began to dump its hydrogen and helium onto the smaller star.

The evolving star became a white dwarf, while the smaller star grew bigger in size and engulfed the white dwarf. The outer layers of the two stars ejected and left behind a white dwarf and helium core of partner star. The white dwarf then pulled matter from the dying star and ended as a mini-explosion. The system now survives as a zombie star.