Scientists observe the nearest supernova since 2014

"The cool thing about the spectropolarimetry is that we get some indication of the shape and extent  of the circumstellar material."

The data acquired by the researchers indicates that the supergiant star was about 10 to 20 times larger than our already massive sun and that its explosion left behind a dense neutron star or a black hole.

The find was supported by another group of astronomers led by Ryan Chornock, a UC Berkeley adjunct associate professor of astronomy. They used the same telescope at Lick Observatory to report that the supernova had shed gas for the previous three to six years before its demise.

A perfect laboratory

"I think this supernova is going to make a lot of us think in much more detail about the subtleties of the whole population of red supergiants that lose a lot of material before explosion and challenge our assumptions about mass loss," said graduate student Wynn Jacobson-Galán who was part of Chornock’s team.

"This was a perfect laboratory to understand in more detail the geometry of these explosions and the geometry of mass loss, something we already felt ignorant about."

Now both teams of researchers have submitted papers to The Astrophysical Journal Letters detailing their rare and unique corelated observations 

"In the world of Type II supernovae, it's very rare to have basically every wavelength detected, from hard X-rays to soft X-rays to ultraviolet. to optical, near-infrared, radio, millimeter. So it's really a rare and unique opportunity," said Raffaella Margutti, a Berkeley professor of physics and of astronomy who was also part of Chornock’s team.

"These papers are the beginning of a story, the first chapter. Now we are writing the other chapters of the story of that star."

The studies will now contribute to a broader picture and understanding of exactly how our universe evolves and operates. They may also reveal some of the secrets that supernovas carry.

"The big-picture question here is we want to connect how a star lives with how a star dies," Chornock said. 

"Given the proximity of this event, it will allow us to challenge the simplifying assumptions that we have to make in most of the other supernovae we study. We have such a wealth of detail that we're going to have to figure out how to fit it all together to understand this particular object, and then that will inform our understanding of the broader universe."