Artist's impression of a supernova explosion. Credit: European Southern Observatory/M. Kornmesser. |
Astronomers have identified a remarkable star, at least 50 times more massive than the Sun, which simply will not die. When massive stars come to the end of their life cycles, their final moments are usually marked by catastrophic and destructive explosions known as supernovae. Scientists have observed thousands of these titanic events, and in every case previously seen, they resulted in the death of the star.
However, an international
team of researchers has discovered a star that exploded multiple times over a
period of 50 years, a finding that challenges everything we know about the
death of stars.
A representational image of a supernova explosion. iStock |
The exceptional supernova,
known as iPTF14hls, was first spotted by astronomers in 2014, although at first
there appeared to be nothing out of the ordinary about it. But several months
later, researchers at the Los Cumbres Observatory observed something they had
never seen before – the supernova was becoming brighter after the initial
explosion had faded.
Normally, supernovae reach
peak brightness before fading over around 100 days. But iPTF14hls became
brighter and dimmer five times over the course of two years.
Furthermore, when
astronomers subsequently examined archival data they were astonished to find
evidence to suggest that the star had actually exploded in 1954 and survived.
The findings are published
in the journal Nature.
"This supernova breaks
everything we thought we knew about how they work. It's the biggest puzzle I've
encountered in almost a decade of studying stellar explosions," said Iair
Arcavi, lead author of the study from the of University of California Santa
Barbara and Las Cumbres Observatory.
Supernova iPTF14hls may the
first example of a so-called "pulsational pair instability
supernova". This occurs when massive stars become so hot in their cores
that energy is converted into antimatter, causing an explosion that blows off the
outer layers while leaving the core intact.
This process can repeat over
decades before the star explodes one final time, collapsing in on itself and
turning into a black hole. However, there is also the chance that this
supernova may be something new entirely. After all, the "pulsational
pair" theory does not fully explain all the data researchers have gathered
for the event.
Andy Howell, leader of the
Las Cumbres supernova group and co-author of the study, added: "These
explosions were only expected to be seen in the early universe and should be
extinct today. This is like finding a dinosaur still alive today. If you found
one, you would question whether it truly was a dinosaur."
Astronomers at Las Cumbres
continue to monitor iPTF14hls, which is still bright three years after being
discovered.
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