An Exploding Star Is Caught in the Act

When an automated sky survey bags a three-hour old supernova, astronomers around the world spring into action and find the smoking gun.

Published on 2/13/2017 at 11:29 AM

Before their explosive finales, dying stars are hard to find, much to the frustration of scientists who would like to learn more about what makes a massive star suddenly collapse.

The resulting supernova explosion seeds a galaxy with iron, silicon and other elements forged by the nuclear fusion of hydrogen and helium in the doomed star's core.

Thanks to a bit of serendipity and quick work by astronomers, the death of a massive star on Oct. 6, 2013 did not go unnoticed.

An automated wide-angle sky survey at California's Palamar Observatory spotted a very young supernova in the spiral galaxy NGC 7610, located about 160 million light years away.

Realizing the supernova wasn't in the previous night's scans, astrophysicist Ofer Yaron at Israel's Weizmann Institute of Science and colleagues alerted fellow astronomers to pick up the hunt.

By coincidence, California Institute of Technology astronomer Dan Perley was making spectroscopic observations with the Keck telescope in Hawaii and turned his attention to the newly found supernova. He was able to collect data and analyze what had been expelled from the star in the year or so before its demise.

"Direct observation of these processes is challenging, as stars in these brief final stages are rare," Yaron and colleagues write in a paper published in this week's Nature Astronomy.

The scientists discovered that in the year before the star burst, it had ejected the equivalent of 1,000 Earth masses.

Follow-up observations by NASA's Swift satellite in X-ray and ultraviolet light enabled the team to map the distribution of the material ejected before the star went supernova.

"Catching and being able to obtain significant follow-up observations of a supernova explosion as early as possible, in its very youth (first minutes to hours after explosion), is crucial for shedding light on our understanding of both the latest stages of evolution of massive stars and understanding of the explosion mechanisms themselves," Yaron wrote in an email to Seeker.

In the Keck data, scientists found the chemical fingerprints of highly ionized oxygen and other materials.

"We caught this event when (it was) extremely young and hot. These are exciting observations by themselves, before even going to the implications of the existence of the nearby and confined distribution of material that was expelled from the progenitor star," Yaron said.

"Such observed evidences provide theorists and modelers of stellar evolution with crucial inputs and constraints in order to ultimately understand the exact mechanisms that effect the latest stages in the evolution of the star and also the understanding of the supernova explosion itself. Both of these are still not understood and are the topics of major ongoing research," Yaron added.

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