Scientists capture earliest supernova spectra ever

Boom. (Photographer: NASA Goddard Space Flight Center).

by Matthew Jordan

Scientists recently managed to capture observations of a star undergoing a supernova just three hours after the process began. The study, published on Monday in Nature Physics, provides a new view of the lead-up to and the immediate results of a supernova explosion.

The supernova, designated SN 2013s, was originally discovered in 2013 by the iPTF (Intermediate Palomar Transient Factory), which immediately alerted a network of facilities around the world to capture the explosive death of the star.

Exhumed material travelling at 10,000 km/s typically obscures the region within days, hiding evidence of the collapse. The quick flagging allowed scientists to get a glimpse of the dense circumstellar disk of material blown off as a large star enters its swan song.

“Those are the earliest spectra ever taken of a supernova explosion,” said study author and Weizmann Institute astrophysicist Ofer Yaron. “It’s from those early spectra that we managed to learn so much about the distribution of the material that we found to exist around this exploding supernova.”

The event itself is a Type II supernova, meaning that the original star was likely a red supergiant. It’s expected that it would have had a mass of at least ten times that of the Sun and a radius hundreds of times larger. It can be located to the galaxy NGC 7610, approximately 160 million light years away from our own galaxy. While the light has only just reached our solar system now, the supernova must have occurred over 100 million years ago.

The survey got a sight of the ionisation shockwave of the supernova through the mass exhausted by the supergiant. The spectra analysed showed that the star had been shedding matter for years before the collapse.

While it is generally known how stars of this type perish, the details of the mass loss of such stars prior to exploding and the effect of this on the stellar core are for the most part unknown, making this new information extremely valuable.

“It’s as if the star knows that it is finishing its life soon, that it will die soon, and it puffs some material outside in its last breaths,” Yaron commented. “It’s like volcanoes or geysers where, in many cases, you will see some bubbling of material and ejection of lava on a smaller scale before the real eruption. Studies like this strengthen our understanding of the very final stages of massive stars, showing that [are] hints of the coming supernova explosion.”

More early sights of these stellar events are likely to follow in the future. Later this year, the iPTF will be replaced by the Zwicky Transient Facility (ZTF), capable of scanning a 3750 square degree view of the sky per hour. This would allow almost the entire visible sky to be scanned in a single night, making such transients much more likely to be detected.

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