Astronomers Observe a 'Zombie' Supernova That Keeps Exploding
Astronomers monitoring the faraway supernova named iPTF14hls have noticed some interesting behavior. While most dying stars get things over with pretty quickly, ballooning in a final burst of light before dissipating over a few short months, this supernova seems to be repeatedly exploding over and over again. And it's been shining for over three years, longer than the 100 days that a typical supernova will last, leaving astronomers puzzled.
Dubbed a "zombie" supernova by some media outlets, iPTF14hls has been continuously growing brighter and dimmer now since it was first discovered in 2014, but there's even evidence than the star might have still been in a supernova phase all the way back in 1954, as records indicate that astronomers may have spotted something in the same position in the sky that was going through a similar explosion cycle. The findings were documented in a recent study published in Nature.
What's particularly fun about iPTF14hls is that it was discovered almost by accident. When Iair Arcavi, a professor at the University of California, Santa Barbara, first spotted iPTF14hl, he instantly dismissed it as yet another exploding star - nothing to get too worked up about. The dying star appeared to be fading, indicating that the majority of its last flash of light was ebbing away, as it would soon collapse down into nothingness.
In 2015, Arcavi asked a student, Zheng Chuen Wong, to check on various astronomical discoveries he'd spotted over the years, just to see what was going on. Lo and behold, iPTF14hls was still going strong, and was actually brighter than it had been the previous year, invalidating everything previously assumed about the way that supernovae work.
And even beyond that, the supernova was aging extremely slowly, going off measurements taken of how quickly the debris and surrounding materials were spinning around it. After 600 days had passed, it was acting like an average 60-day old supernova, something that doesn't match any existing records at the moment. According to Arcavi:
There are a lot of different theories as to what might be causing iPTF14hls to explode repeatedly. Some suspect that the star might be so large that its own weight is triggering a new supernova explosion every time it begins to quieten down too much.
While another theory - again, assuming that this star is exceptionally large - suggests that the phenomenon is caused by the remnants of iPTF14hls forming a neutron star right at the moment of collapse, causing the cycle to kick off again every time.
An instrument built by our own Nick Konidaris was key to analyzing the light emitted by #ZombieStar iPTF14hls, a #supernova which dimmed and brightened at least 5 times over 3 years. https://t.co/0qEJypIkqn pic.twitter.com/eGUQEbNRHN— Carnegie Astronomy (@CarnegieAstro) November 8, 2017
Whatever's going on, we don't know for sure. Astronomers are going to continue to study iPTF14hls to see what other odd behavior this immortal supernova might show off, but in the absence of concrete data on the star beyond its brightness in the night's sky, there's not an awful lot to go on as of yet.