Astronomers have spotted the brightest and most energetic supernova ever recorded. The event, known as SN2016aps, may have been the result of two stars merging and then exploding, before the dust had completely settled.
Supernovae are among the most energetic events in the cosmos, occurring when stars of a certain mass exhaust their fuel. At that point, they throw off their outer layers in a spectacular light show, while their core collapses into an incredibly dense object such as a white dwarf, neutron star or black hole.
Supernovae themselves are a very common sight for astronomers, but SN2016aps was special. It was at least twice as bright and energetic as any other supernova observed, and seemed to involve far more mass than usual.
“We can measure supernovae using two scales – the total energy of the explosion, and the amount of that energy that is emitted as observable light, or radiation,” explains Matt Nicholl, lead author of a new study describing the event. “In a typical supernova, the radiation is less than one percent of the total energy. But in SN2016aps, we found the radiation was five times the explosion energy of a normal-sized supernova. This is the most light we have ever seen emitted by a supernova.”
SN2016aps was first spotted in 2016 by Pan-STARRS in Hawaii, and it was observed for two years until it finally faded to about one percent of its peak brightness. Data gathered during that time let the researchers begin to piece together what happened.
Normally, supernovae involve between eight and 15 solar masses, but the team calculated that SN2016aps involved 50 to 100 times the mass of the Sun. On top of that, the light spectrum suggested that the extra brightness came from the supernova colliding with another shell of gas.
Both of these factors can be explained by a “pulsational pair-instability” event, which has been theorized for decades but never observed. Essentially, the story goes that two stars collided in the past, creating a new, unstable star in the process. That, in turn, would have sown the seeds for such a powerful supernova to follow.
“Stars with extremely large mass undergo violent pulsations before they die, shaking off a giant gas shell,” says Nicholl. “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. 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.”
The research was published in the journal Nature Astronomy.
Source: University of Birmingham