Even given the trillions and trillions of stars that exist in the known universe, scientists had yet to witness a star exploding with their own eyes until recently. Because of the rarity of the event as well as the long life span of stars, in general, being alive as a human is too short of a period to be lucky enough to ever catch one happening. Thanks to the Kepler exoplanet-hunting space telescope, however, one such event was spotted by scientists; even if the witnesses only saw it happening only 1.2 billion years later.
A supernova is an event where a star larger than 25 solar masses reaches the end of its life and explodes under the pressure of its own weight. As a star uses resources to create energy, it slowly transforms its vast quantities of hydrogen into helium, then the newly transformed helium into more and more complex elements such as carbon, oxygen, magnesium and so on.
However, when this fusion process reaches the stage in which it creates iron, the star slowly starts running out of fuel. Because iron fusion ends up absorbing energy and making the core temperature drop, the star gets heavier and heavier until it starts collapsing under its own weight and gravity. After there’s nothing left but iron inside, the star becomes very small then explodes.
A team of astrophysicists led by Peter Garnavich, a professor at the University of Notre Dame, however, managed to witness the shockwave sent out by an exploding star and are currently preparing to publish a study in the Astrophysical Journal regarding the event. But spotting such a shockwave is not a process that you just see.
The shockwave itself lasts less than an hour, but it still meant that scientists had to study data on the light recorded by the Kepler space telescope every 30 minutes over the length of 3 entire years in a zone as large as 500 distant galaxies. On such a huge scale of data, the scientists were lucky enough to spot not one, but two such supernovae, which was even more than expected.
The shockwaves that they spotted came from two massive red super giants – one called KSN 2011a and KSN 2011d – that are located nearly a billion light years away and are approximately 300 and 500 times the size of our sun, respectively.
While the actually spotting did not involve physically watching a star explode, and the deduction was made upon close study of an enormous amount of data, the University of Notre Dame released a concept video of what one of the stars exploding may have looked like. You can watch it here.
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