When stars reach the end of their lifetimes, they are torn apart by a massive explosion known as a supernova. These huge shockwaves rip through surrounding space and disperse many of the heavier elements that have built up within the star over its lifetime.
Despite these processes being integral to understanding of the evolution of stars, galaxies and even the universe, supernovas are transient occurrences and are hard to catch in the act.
Reporting in the Monthly Notices of the Royal Astronomical Society, a collaboration of researchers from Liverpool John Moores University in the UK and the University of Montpellier in France, have used archival telescope data to better constrain the timeline leading up to the star’s demise, resulting in an ‘early supernova warning’ system of sorts.
Just as they reach the final few months of their lives, massive stars (those between eight and 20 times the mass of our own Sun) suddenly dim in visible wavelengths. This dramatic faintness is the result of the accumulation of a ‘cocoon’ of material around the red supergiant star. “The dense material almost completely obscures the star, making it 100 times fainter in the visible part of the spectrum”, says Dr Benjamin Davies an astrophysicist at Liverpool John Moores University and lead author of the paper. “This means that, the day before the star explodes, you likely wouldn’t be able to see it was there.”
Davies investigated archival telescope data of fields of view that included stars that went on to go supernova after about a year after the image was taken. These stars were not obscured, suggesting that the cocoon-building process occurs in less than a year – surprisingly rapid.
Using this information, Davies was able to create detailed simulations showing how the red supergiants might look when encased in their shrouds, thereby giving astronomers a chance to detect stars that are booked in for a final meeting with their maker within the order of months.
“Until now, we’ve only been able to get detailed observations of supernovae hours after they’ve already happened,” says Davies. “With this early-warning system we can get ready to observe them real-time, to point the world’s best telescopes at the precursor stars, and watch them getting literally ripped apart in front of our eyes.”