Scientists enthralled by biggest star explosion ever observed
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[April 15, 2020]
By Will Dunham
WASHINGTON (Reuters) - Scientists have
observed the biggest supernova - stellar explosion - ever detected, the
violent death of a huge star up to 100 times more massive than our sun
in a faraway galaxy.
The supernova, releasing twice as much energy as any other stellar
explosion observed to date, occurred about 4.6 billion light years from
Earth in a relatively small galaxy, scientists said. A light year is the
distance light travels in a year, 5.9 trillion miles (9.5 trillion km).
It might represent, they added, a type of supernova that until now has
only been theorized.
Astrophysicist Matt Nicholl of the University of Birmingham in England
said two very massive stars - each about 50 times the sun's mass - may
have merged to make one extremely massive star roughly 1,000 years
before the explosion. They had been part of what is called a binary
system with two stars gravitationally bound to each other.
The merged star exploded in a supernova, formally named SN2016aps,
inside a very dense and hydrogen-rich envelope.
"We found that the supernova was able to become so bright because of a
powerful collision between the debris ejected by the explosion and a
shell of gas shaken off by the star a few years earlier," said Nicholl,
lead author of the study published this week in the journal Nature
Astronomy.
Stars die in various different ways depending on their size and other
properties. When a massive star - more than eight times the mass of our
sun - uses up its fuel, it cools off and its core collapses, triggering
shock waves that cause its outer layer to explode so violently that it
can outshine entire galaxies.
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An artist's impression of supernova SN2016aps, provided by
Northwestern University April 13, 2020. Aaron Geller/Northwestern
University/Handout via REUTERS.
The researchers, who observed the explosion for two years until it
diminished to 1 percent of its maximum brightness, said it may have
been an example of an extremely rare "pulsational pair-instability"
supernova.
"Pulsational pair-instability is when very massive stars undergo
pulsations which eject material away from the star," said study
co-author Peter Blanchard, a postdoctoral fellow in astrophysics at
Northwestern University in Illinois.
"This discovery shows that there are many exciting and new phenomena
left to be uncovered in the universe," Blanchard added.
Very massive stars like this one were probably more common early in
the universe's history, Nicholl said.
"The nature of those first stars is one of the big questions in
astronomy," Nicholl added. "In astronomy, seeing things further away
means looking back further and further in time. So we might actually
be able to see the very first stars if they explode in a similar
manner to this one. Now we know what to look for."
(Reporting by Will Dunham; Editing by Sandra Maler)
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