A star that reaches the end of life continues to shine, say astronomers, who are now wondering whether our understanding of the stages of stellar evolution should be questioned.
Powerful star explosions known as supernova usually mark the death of stars, these have been observed in all cases. But astronomers at Las Cumbres Observatory have discovered a remarkable exception — a star that exploded multiple times over a period of more than fifty years.
This supernova, named iPTF14hls, was first discovered in September 2014. At the time, it was not abnormal and was considered an ordinary supernova. Several months later, LCO astronomers noticed something that they had never seen before — the supernova was growing brighter again after it had faded.
A normal supernova rises to peak brightness and fades over approximately 100 days. Supernova iPTF14hls, on the other hand, grew brighter and dimmer at least five times over two years.
“This supernova breaks everything we thought we knew about how they work,” said lead author Iair Arcavi, a NASA Einstein postdoctoral fellow in UC Santa Barbara’s Department of Physics and at LCO. “It’s the biggest puzzle I’ve encountered in almost a decade of studying stellar explosions.”
According to the information gathered, this star would be at least 50 times more massive than the Sun. It could be the largest stellar explosion ever detected. Moreover, the magnitude of this explosion may explain why it can not be associated with any of the traditional theories of star death.
The global telescope network of Las Cumbres Observatory is uniquely designed for this type of continuous observation. LCO has observed this supernova every few days for several years. The long-term consistent monitoring is essential for the study of this very unusual event.