Daily paper summaries

Observing the Next Galactic Supernova

Title: Observing the Next Galactic Supernova
Authors: Scott Adams, C.S. Kochanek, John Beacom, Mark Vagins, K.Z. Stanek
First Author’s Institution: The Ohio State University

Kepler's drawing of SN 1604. The supernova is the star with the letter "N" pointing at it. in Ophiucus' left foot.

Kepler’s drawing of SN 1604. The supernova is the star with the letter “N” pointing at it. in Ophiucus’ left foot.

The last time a supernova was observed within the Milky Way was in 1604 by Johannes Kepler, and was only appreciated by the human eye, since optical telescopes and other measurement devices had not yet been invented. Despite a lack of hard observational data, astronomers have a theoretical framework to describe the processes that occur during a supernova, and numerical simulations are always growing more detailed and sophisticated. Still, without observation, neither theory nor numerical result can be put to the test.

While supernovae in our galaxy are relatively rare, extragalactic supernovae are not. That is because there are countless galaxies that have supernova rates similar to that of the Milky Way. But, due to their distance from Earth are not resolvable and offer little insight into the mechanisms at work during the explosion. Although astronomers haven’t observed supernovae in the Milky Way for several hundred years (read on to find out why this may be), the good news here is that astronomers are developing methods to be ready when the next one happens..

The authors of this paper discuss the likelihood of predicting where in the sky the next supernova will appear and how it should be observed. The trick to predicting their appearance lies with neutrinos–the tiny, light-weight, high-speed, neutral particles that pervade the whole of the Universe. We’ve written about neutrinos a few times here at Astrobites, most recently earlier this week. Neutrinos are produced in a variety of contexts, and they happen to play a special part in the supernova process.

During the collapse of a massive star’s core, neutrinos are produced in huge quantities. Because they are so tiny and interact so weakly with their surroundings, they leave the star before the shock wave that produces the explosion reaches the outer layers of the star. That is, a burst of neutrinos leave the star before the explosion becomes visible. A handful of neutrino detectors around the globe are capable of detecting this neutrino burst, and are part of a network called SNEWS (The SuperNova Early Warning System) that will alert astronomers when that burst is observed.

Astronomers will then have minutes or hours or maybe even days to position their telescopes before the light from the explosion reaches Earth. But, even after all of that, what are the odds that we could actually see the explosion? After all, the predicted occurrence rate is 2-3 per century, yet the last observed explosion happened in 1604. What gives? The most likely scenario is that galactic supernovae have occurred since then, but their visibility has been obscured by dust in the galactic plane.

The authors conducted a statistical study of possible galactic supernovae and found that with our modern fleet of optical telescopes and neutrino observatories, the probability of being able to observe the next galactic supernova is approximately 100 percent, even in visible wavelengths thanks to the sensitivity of space telescopes. This is exciting news for any astronomer who’s anxious to have the once-in-a-career opportunity to study a supernova “up close”. Until then, patience.

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Justin Vasel

Justin is a physics graduate student at Indiana University. He has been involved with the HALO experiment at SNOLAB in Sudbury, Canada. As part of the SuperNova Early Warning System (SNEWS), HALO will detect neutrinos produced by supernovae and help alert the astronomical community. Justin’s other research interests include heliophysics and the formation of massive stars.

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