Star exploded faster than any others on record

Astronomers have captured an extremely quick supernova known as KSN 2015K that disappeared within 25 days.
By Joseph Scalise | Mar 28, 2018
A group of international researchers have observed the fastest supernova on record, according to a new studypublished in the journal Nature Astronomy.

Typically, a supernova -- which occurs when a star explodes -- is a long process that can last for months on end. However, in the new research scientists analyzed a supernova known as KSN 2015K and found that it occured much faster than most explosions.

The phenomenon both peaked in brightness and completely disappeared in less than a month. That means the entire process happened 10 times faster than other supernovae of similar brightness.

Researchers are not sure how the blast came and went so quickly, but they think it is likely because most of the eruption was blocked by a mess of gas and dust it had already ejected. Then, once the debris blasted away, the entire event became visible.

Researchers have captured events like supernova KSN 2015K before. The eruptions, known as fast-evolving luminous transients (FELTs) always stun astronomers because they break the perceptions of common supernova models.

The Kepler telescope captured KSN 2015K in 2015, giving researchers brand new insight into how FELTs work.

"Usually you might have 1 or 2, maybe 3 measurements in 2.2 days, but we have a whole series of really strong measurements that allow us to test different models," said study co-author Armin Rest, a researcher at the Space Telescope Science Institute, according to New Scientist.

In 2 days the blast rose to peak brightness, and within a week it dropped to half that. In 25 days it was completely gone.

The telescope's observations showed that the light curve matched that of a supernova after the star exploded, but the event did not have any of the build up that marks such events. That is why the team believed it was originally blocked by dust.

Stars eject most of their mass as they die. Though such dust typically sits around the star, it could potentially block a supernova if the star was dense enough. However, that then raises the question of how the debris could create a dense cocoon of material around an unstable star such a short time before its death.

The team does not have an answer to that question, but they do have potential explanations. For instance, as KSN 2015K has very little nickel, it could be that an asymptotic giant branch star -- a low-to-intermediate-mass red giant that gets brighter as it dies -- created the cloud.

Under that theory, the collapsed star core would have released a gigantic amount of kinetic energy that converted into light when it slammed into the cocoon.

The team plans to follow up on their observations to see what else they can discover about both KSN 2015K and FELTs in general.

"Now these observations of KSN 2015K have shown that the death throes of stars can be even more rapid than we thought," wrote astrophysicist JJ Eldridge, a researcher at the University of Auckland in an accompanying editorial, according toScience Alert.

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