An extremely rare supernova that outshines all others

Pulsational pair-instability supernova.

An international team of astronomers led by the University of Birmingham has recently spotted an extremely rare ‘pulsational pair-instability’ supernova that shines at least twice as bright and energetic, and likely much more massive than other supernovas recorded till now.

Dubbed as SN2016aps, the supernova is believed to form from two massive merging stars before the explosion.

Supernova 2016aps was first detected in data from the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), a large-scale astronomical survey program. The team also used data from the Hubble Space Telescope, the Keck and Gemini Observatories, in Hawaii, and the MDM and MMT Observatories in Arizona. Other collaborating institutions included Stockholm University, Copenhagen University, California Institute of Technology, and Space Telescope Science Institute.

Dr. Matt Nicholl, of the School of Physics and Astronomy and the Institute of Gravitational Wave Astronomy at the University of Birmingham, is the lead author of the study. 

He explains“We can measure supernovae using two scales – the total energy of the explosion, and the amount of that energy that is emitted as visible light, or radiation.”

“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.”

By examining the light spectrum, scientists confirmed that the explosion was powered by a collision between the supernova and a massive shell of gas shed by the star in the years before it exploded. Furthermore, it has mass 50 to 100 times greater than our sun.

Dr. Peter Blanchard, from Northwestern University and a co-author of the study, said, “While many supernovae are discovered every night, most are in massive galaxies. This one immediately stood out for further observations because it seemed to be in the middle of nowhere. We weren’t able to see the galaxy where this star was born until after the supernova light had faded.”

Dr. Nicholl further added, “SN2016aps also contained another puzzle. The gas we detected was mostly hydrogen – but such a massive star would usually have lost all of its hydrogens 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.”

Professor Edo Berger, a co-author from Harvard University, said, “Finding this extraordinary supernova couldn’t have come at a better time. Now that we know 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 can look back in time to the deaths of the very first stars in the Universe.”

Journal Reference:
  1. An extremely energetic supernova from a very massive star in a dense medium. DOI: 10.1038/s41550-020-1066-7

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