Scientists Just Observed One of the Fastest, Brightest Supernovas in History
Supernovas pack a lot of punch, to put it lightly—they can outshine galaxies and expel more energy than our Sun's lifetime output, making them the largest explosions in space. Though they usually take weeks or months to reach maximum brightness (and longer to fade away), astronomers recently observed a star called KSN 2015K whose supernova flared up to max brightness over in just 2.2 days and dimmed to half of that in 6.8 days, placing it among the fastest, brightest supernovas on record.
Fast supernovas are usually not as bright as the slower ones, which generally come from massive explosions. Fast, dim supernovas, on the other hand, are usually the result of a weaker triggering event, like a partial explosion. KSN 2015K's rapid, bright supernova changes things, though—astronomers had to figure out what was unique about the star to allow it to get that bright that fast. The hypothesis they came up with is this: when the star finally died, it expelled a huge cloud of gas, which collected around it. About two months later, the star actually exploded, blowing chunks of debris into the cloud of gas, which caused a giant shockwave that produced the light of the supernova.
According to Armin Rest of the Space Telescope Science Institute in Baltimore, "When the explosion hits the shell, that's when all this energy that we see is created," says Rest. "All hell breaks loose once that happens."
Aside from being incredibly fast and bright, the KSN 2015K supernova was also one of the best-observed ever. Rest's team was able to take photos of the supernova about every 30 minutes over the 2.2-day period that it reached max brightness. "Usually you might have 1 or 2, maybe 3 measurements in 2.2 days, but we have a whole series of really strong measurements that allow us to test different models," said Rest.