• Researchers spotted a unique supernova that's said to be the brightest of its kind
  • It's possible that it was exploding in an AGB star that was turning into a planetary nebula
  • Having another power source caused the supernova to shine even more brightly

An international team of researchers spotted a unique supernova that's the brightest of its kind. What could have caused it to shine that bright?

A supernova is thought of as the "last hurrah" of a star at the end of its life but there are actually several types of this cosmic explosion. Type Ia supernovae, for instance, are believed to be triggered by the explosion of a white dwarf in a binary system due to accretion or a merger.

In a new study, a 37-member international research team spotted a rather unique Type Ia supernova from 100 million light years away. Dubbed "supernova LSQ14fmg", it is said to be the brightest explosion of its class and it is also brightening exceptionally slowly.

"The near-infrared light curves peak brighter than −20.5 mag in the J and H bands, far more luminous than any 03fg-like SNe Ia with near-infrared observations," the researchers wrote in their study published in The Astrophysical Journal.

According to a Florida State University (FSU) news release, the light from Type Ia supernovae tends to rise and fall in a matter of weeks, brightening when the nickel produced in the explosion is more exposed and becoming fainter when the nickel decays.

But based on their observations, the researchers found that LSQ14fmg appears to be interacting with some other material that releases light with the decaying nickel. This suggests that there was another power source in the vicinity apart from the radioactive decay of nickel.

According to the researchers, it's possible that the supernova was actually happening in an asymptotic giant branch (AGB) star that was already becoming a planetary nebula, the class of nebulae with an expanding shell of ionized gas expelled by stars late in their lives.

Planetary nebulae have a luminous gas ring that is ionized by the ultraviolet radiation of very hot central stars. The researchers believe that when the supernova is triggered by the merger of the AGB core and a white dwarf, it interacts with this luminous ring and produces the extra light, thus becoming the brightest of its kind.

"This is the first strong observational proof that a Type Ia supernova can explode in a post-AGB or proto-planetary-nebula system and is an important step in understanding the origins of Type Ia supernovae," study lead professor Eric Hsiao of FSU said in the news release.

supernova-breakout The brilliant flash of an exploding star's shockwave — what astronomers call the hock breakout — is illustrated in an artist concept. Photo: NASA/JPL