You might think having the opportunity to watch a star go supernova would be a rather rare occurrence—in fact, it really is—but there’s one star that has been exploding over and over again. Well, not really. Scientists think it exploded once 9 billion years ago, but thanks to a trick of optics, they’ve been able to watch the explosion in reruns.
Help for the Hubble Space Telescope
Dennis Overbye of The New York Times compares the phenomenon to the 1993 film Groundhog Day, in which a character played by Bill Murray experiences the same day repeatedly. The star that exploded is so far away from Earth that it requires the help of several galaxies in order for the Hubble Space Telescope to be able to see it.
Four of the galaxies create the shape of what scientists call an Einstein Cross. They surround another galaxy, and since each of those galaxies reflect a different angle of the light rays from the explosion, each of them send an image of a different moment of the explosion.
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Supernovae are rare
Supernova experts say being able to watch one is indeed a rare event that happens only about every hundred years or so. When a star explodes, it is one of the most violent events in the universe and the brightest, outshining entire galaxies. Astronomers say the explosions send particles into the universe that end up forming new worlds and leave black holes behind.
Patrick Kelly with the University of California, Berkeley discovered the rerun supernova by examining images captured by the Hubble Space Telescope in November. He is the lead author on the paper about the findings of his research on those images, which was published in the journal Science.
Same supernova to repeat again
This is the first time scientists have been able to see a supernova repeat itself multiple times. They had scene supernova captured through “gravitational lenses” in the past, however. The cluster of galaxies around the exploding star created multiple gravitational lenses, which is what allowed them to see the supernova four times.
Astronomers expect this same supernova to pop up yet again sometime in the next ten years. They were able to time the delays between each of the explosion’s appearances. They believe by continuing to measure the time between each appearance of the supernova that they will be able to better measure the speed at which the universe seems to be expanding. They also want to map the dark matter, which is what most of the universe is made of.