When a massive star runs out of the fuel it needs to keep shining, it ends its life with an enormous explosion, known as a supernova. The process can leave remnants, either a neutron star or a black hole, shining for up to 100 days—or at least that’s what we used to think.
The longest supernova explosion ever observed—more than 600 days—could change the way we think about the evolution of stars. In September 2014, Iair Arcavi and colleagues were using Intermediate Palomar Transient Factory telescope near San Diego, when they discovered what they thought was a regular type II supernova. They named it iPF14hls. It was later flagged for special attention when they noticed it was failing to decline.
A supernova lasting more than 130 days is extraordinarily rare. Rather than fading, this star grew brighter and then dimmer, and then brighter again—varying by as much as 50 percent on an irregular timescale—almost as if it were exploding over and over again.
“As of now, no detailed model has been published that can explain the observed emission and constant temperature of iPTF14hls, let alone the possible eruption 60 years before the supernova,” Woosley said.
Further study will likely teach us something new about stars around 40 times the mass of the sun.
“For now, the supernova offers astronomers their greatest thrill: something they do not understand,” Woosley said.