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Astronomers have detected the brightest supernova yet, twice as bright as any seen before. So bright, in fact, that the explosion released tens of times the energy that the Sun will produce in its entire lifetime. The event, known SN2016aps, has been put forward as evidence of a rare "pulsational pair-instability" supernova.
These events have been predicted theoretically but never observed before. Reporting in Nature Astronomy the team followed the light of the event for two years, using the data to understand the explosion and estimate the properties of its progenitor. The mass of the supernova was between 50 and 100 times the mass of the Sun (solar masses), much higher than your run-of-the-mill supernova, which is usually between 8 and 15 solar masses.
The incredible explosion was possibly the result of two stars merging, but the increase in energy is likely due to a different collision between the supernova and the gas released by one or both stars before their demise, creating the “perfect storm” that was this event.
"Stars with extremely large mass undergo violent pulsations before they die, shaking off a giant gas shell. This can be powered by a process called the pair-instability, which has been a topic of speculation for physicists for the last 50 years," lead author Dr Matt Nicholl from the University of Birmingham said in a statement. "If the supernova gets the timing right, it can catch up to this shell and release a huge amount of energy in the collision. We think this is one of the most compelling candidates for this process yet observed, and probably the most massive."
"SN2016aps also contained another puzzle," added Dr Nicholl. "The gas we detected was mostly hydrogen – but such a massive star would usually have lost all of its hydrogen via stellar winds long before it started pulsating. One explanation is that two slightly less massive stars of around, say 60 solar masses, had merged before the explosion. The lower mass stars hold onto their hydrogen for longer, while their combined mass is high enough to trigger the pair-instability."
The estimated energy released of this supernova is just slightly higher than ASASSN-15lh, the previous record holder for most powerful supernova. There have been questions surrounding the true nature of ASASSN-15lh, as some have proposed it was a supermassive black hole-related event since it was located close to the core of its galaxy. SN2016aps instead appeared to be far removed from its galaxy's supermassive black hole, making its supernova claim that much stronger.
To truly understand these objects we need more observations, and upcoming telescopes like the James Webb Space Telescope should be up to the task of doing just that.
