Astronomers have pored over a supernova that occurred about 11.5 billion years ago, when a distant star about 530 times more massive than our sun perished in a violent explosion that blew its gaseous outer layers into the surrounding universe.
Scientists report that NASA’s Hubble Space Telescope took three images in eight days, starting just hours after the explosion. That’s an impressive feat, considering how long the explosion had been going on.
These images provide the first detailed look at a supernova very early in the history of the universe, when it was less than a fifth of its current age, and the first look at a rapidly cooling supernova after its initial explosion in a series of images . .
“Supernovae expand and cool, then change color from a warm blue to a cool red,” said Patrick Kelly, a professor of astronomy at the University of Minnesota.
Located in a dwarf galaxy, the star explodes at the end of its relatively short life as a red giant.
“Red giant planets are bright, big, big stars, but they’re much cooler than most other massive stars, that’s why they’re red,” Chen said. “Once the red supergiant has exhausted the fusion energy in its core, the core will collapse and the supernova explosion will blow away the star’s outer layer, its hydrogen shell.”
Six hours after the original explosion, the first images reveal it started out small but extremely hot, with temperatures reaching nearly 99,725 degrees Celsius.
The second image was taken about two days later and the third image was taken about six days later. These two images show the expansion of gaseous matter emitted by the star. The intensity of the explosion has been reduced five times in the second image. The third image shows temperatures up to a tenth of those of the first.
According to Chen, the remains of the exploded stars are most likely neutron stars due to their extreme density.
Hubble was able to take three photos after the explosion at different times due to a phenomenon known as strong gravitational lensing. Galaxy clusters in front of exploding stars, as seen from Earth, exert gravitational forces so strong that they act like lenses, bending and amplifying the supernova’s light.
Read also: NASA’s James Webb Space Telescope has discovered the first galaxies to escape Hubble
“Gravity in a galaxy cluster not only bends the light behind it, but it also delays the time that light travels because the stronger the gravity, the slower the clocks move,” Chen said. In other words, the light beam from a source behind the lens can travel different paths towards us, and so we see more images from that source.
Gravity lensing allowed Kelly to see the rapidly cooling supernova in a series of images, calling it “absolutely stunning.”
“It’s like watching color film of an expanding supernova, which is a much more detailed picture of every known supernova that existed when the universe was a fraction of its current age,” Kelly explained.
“The only other time we’ve detected a first supernova was a very close explosion,” Kelly added. “When astronomers look at more distant objects, they look back in time.”
(With input from Reuters)
