Scientists have observed a small number of supernovas that are slightly less powerful. They call these supernovas Type Iax, as opposed to the more common Type Ia. Astronomers think Type Iax supernovas allow a faint remnant of the exploded white dwarf to remain.
Recently, scientists witnessed a smaller-than-usual supernova using images from the Hubble telescope and telescopes at the Lick Observatory.
After learning about the small supernova in galaxy NGC 1309, which is roughly 108 million light-years away, astronomers were able to go back and look at images of the star leading up to the explosion -- an attempt to understand what causes the type of supernovas that might leave behind a zombie star.
"We were tremendously excited to see a progenitor system for this supernova," Curtis McCully, an astronomer at Rutgers, told Space.com. "No one had ever seen a progenitor system for a white-dwarf supernova in pre-explosion data, so our expectation was that we wouldn't see anything. Nature surprised us, which is always exciting."
McCully is lead author of a study of the supernova and potential zombie star, which was recently published in Nature.
Their observations showed a bright companion star interacting with the white dwarf may have ignited this Type Iax supernova.
"Our results show that at least some white-dwarf supernova explosions arise from a white dwarf that accretes material from a luminous companion star," explained Saurabh Jha, another Rutgers astronomer.
To confirm they've actually witnessed a distinct type of supernova, astronomers will have to wait until 2015, when Hubble will capture imagery of the explosion site once the light from the supernova has faded.
"We also hope to see the remnant zombie star," Jha said.