Brightest supernova ever seen

supernova
Aaron Geller (Northwestern University)

A supernova 4 billion light-years away is the brightest ever recorded, says scientists. 

The SN2016aps supernova was identified by an international team of astronomers led by the University of Birmingham, England and included  experts from Harvard, Northwestern University and Ohio University. 

A supernova is the explosion of a star and it is the largest explosion that takes place in space.

This supernova may have been triggered by two massive stars which merged before the explosion. 

Astronomers watched the explosion for two years, until it faded to 1% of its peak brightness. 

Dr Matt Nicholl, of the University of Birmingham explained: “In a typical supernova, the radiation is less than 1 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.”

The team believes that the unusually energetic nature of the explosion may have helped to make it so bright.

How do you measure a supernova?

Supernovae can be measured by the total energy of the explosion, and the amount of that energy that is released as observable light or radiation, according to lead researcher Dr Matt Nicholl.

"Stars with extremely large mass experience violent pulsations before they die, shaking off a giant gas shell. If the supernova is timed properly, it can reach this shell and release a great deal of energy in the collision. We believe that this is one of the most compelling candidates for this process so far, and probably the biggest," Nicholl said.

Pulsating puzzle

Much of the gas detected initially in SN2016aps was hydrogen, which may “puzzle” scientists as it would be assumed that such a massive star would already have lost much or all its hydrogen through stellar winds long before it started pulsating. However, if two slightly smaller stars merged before the explosion, it leaves scientists with a more plausible scenario, as lower mass stars retain their hydrogen for longer. The combined mass of the stars is likely to have caused the instability. 

 "Now that we know that such energetic explosions occur in nature, NASA's new James Webb Space Telescope will be able to see similar events so far away that we will be able to look back in time on the death of the first stars in the universe," says study co-author Professor Edo Berger.

It is understood that the explosion was driven by a collision between the supernova and the huge layer of gas released by a star in the years before it exploded. 

The explosion was so bright that it made the star appear alone in the universe. "We couldn't see the galaxy where this star was born until the light faded," says Peter Blanchard, another co-author of the study.

Due to the magnitude of its luminosity it was categorised as a “superluminous supernova”, a title given only to two other previously recorded supernovae.

The study was funded through a research grant from the Royal Astronomical Society, along with grants from the National Science Foundation, NASA and the European Union's Horizon 2020 Framework, with the findings published in the journal Nature Astronomy


Reference:

Nicholl, M., Blanchard, P.K., Berger, E. et al., ‘An extremely energetic supernova from a very massive star in a dense medium’, Nature Astronomy, (2020): DOI: 10.1038/s41550-020-1066-7

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