Victor Buso was eager to use the new camera on his telescope. But the amateur astronomer didn’t want to disturb his neighbours with the loud noise of opening his rooftop observatory, so he pointed his telescope through a gap in the enclosure on the night of 20 September 2016.
He trained it on a spiral galaxy called NGC 613, which is around 26 million parsecs (85 million light years) away in the southern sky, and spotted a rapidly brightening blotch of light in the series of images he was taking. Buso and a team of professional astronomers now report in Nature what seems to be the first observation of the very early stages of a supernova1.
The detection was “amazing”, says Norbert Langer, an astrophysicist at the University of Bonn in Germany. The chance of catching this event is smaller than that of hitting the jackpot in a lottery, he says.
The type of supernova the team observed occurs when a massive star runs out of nuclear-fusion fuel in its core. The star then begins to collapse, which compresses protons and electrons together and converts them into neutrons. Astrophysicists theorize that this collapse triggers a shockwave that can take up to a day to reach the star’s surface.
Astronomers have previously seen a supernova around 3 hours after the shockwave reached the surface. However, by taking a series of 20-second exposures over 90 minutes, Buso captured for the first time the rapid increase in brightness that is predicted to occur as the shockwave breaks free.
Buso says that he routinely compares the images he takes from his home in Rosario, Argentina, with online archival photos from other observatories. But that night, he saw differences not just between his pictures and the archive, but also between his first pictures and the ones he took over the course of the next 90 minutes. He thought, “Oh my God, what is this?”, he says.
With the help of a friend, Buso immediately reported his discovery to the International Astronomical Union, a body of professional astronomers. It alerted its members around the world, some of whom rushed to study the supernova.
Catching the supernova so early should mean that astrophysicists can now check their models of how and why supernovas happen, says Langer. For the moment, the Nature paper contains only preliminary findings.
In the near future, projects such as the recently commissioned Zwicky Transient Facility at Palomar Observatory in California might make such early detection commonplace, says astronomer Avishay Gal-Yam of the Weizmann Institute of Science in Rehovot, Israel.
Meanwhile Buso, who spends his days working as a locksmith and many of his nights at his telescope, says that the discovery has made him feel that his efforts were worthwhile. “Many times, you ask yourself, ‘Why do I do this?’ Now I have found the answer.”