By Will Dunham
WASHINGTON (Reuters) – About 11.5 billion years ago, a distant star about 530 times larger than our sun died in a cataclysmic explosion that blew its outer layers of gas into the surrounding cosmos, a documented supernova by astronomers in blow-by-blow detail. .
Researchers said Wednesday that NASA’s Hubble Space Telescope managed to capture three separate images spanning an eight-day period beginning just hours after the detonation – an achievement all the more remarkable given the time and distance at which it occurred.
The images were discovered during a review of archival Hubble observational data from 2010, according to astronomer Wenlei Chen, postdoctoral researcher at the University of Minnesota and lead author of the study published in the journal Nature. .
They offered the first glimpse of a rapidly cooling supernova after the initial explosion in a single set of images and the first in-depth look at a supernova so early in the history of the universe, when it had less than a fifth of his present age.
“The supernova expands and cools, so its color changes from a warm blue to a cool red,” said Patrick Kelly, professor of astronomy at the University of Minnesota and co-author of the study.
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The doomed star, a type called a red supergiant, resided in a dwarf galaxy and exploded at the end of its relatively brief lifespan.
“Red supergiants are bright, massive, and large stars, but they’re much cooler than most other massive stars — that’s why they’re red,” Chen said. “After a red supergiant has exhausted the fusion energy in its core, a core collapse will occur and the supernova explosion will then blast away the outer layers of the star – its hydrogen envelope.”
The first image, from around six hours after the initial explosion, shows the explosion starting off relatively small and extremely hot – around 180,000 degrees Fahrenheit (100,000 degrees Kelvin/99,725 degrees Celsius).
The second image is about two days later and the third is about six days later. In these two images, the gaseous material ejected from the star expands outwards. In the second image, the explosion is only a fifth hotter than in the first. In the third image, it is only a tenth of the heat of the first.
The remnant of the exploded star most likely became an incredibly dense object called a neutron star, Chen said.
A phenomenon called strong gravitational lensing explains how Hubble was able to obtain three images at different times after the explosion. The enormous gravitational pull exerted by a cluster of galaxies in front of the exploding star from Earth’s perspective served as a lens – bending and magnifying the light emanating from the supernova.
“Gravity in the galaxy cluster not only deflects light from behind, but also delays the travel time of light because the stronger the gravity, the slower the clock moves,” Chen said. “In other words, light emission from a single source behind the lens can take multiple paths towards us, and then we see multiple images from the source.”
Kelly called the ability to see the rapidly cooling supernova in a single set of images through gravitational lensing “simply amazing.”
“It’s a bit like seeing a color film reel of the supernova evolve, and it’s a much more detailed picture of any known supernova that existed when the universe was only a small fraction of its current age. “, said Kelly.
“The only other examples where we’ve caught a very early supernova are very close explosions,” Kelly added. “When astronomers see more distant objects, they are looking back in time.”
(Reporting by Will Dunham, editing by Rosalba O’Brien)
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