Enormous, unusual supernova explosion lights up nearby galaxy

23 Jul 2020

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Trinity researchers have helped find the incredibly rare cosmic event of a white-dwarf star exploding as its life comes to an end.

A particularly rare interstellar event has just been seen for only the second time ever. In a paper published to The Astrophysical Journal Letters, researchers from Trinity College Dublin (TCD) helped document the discovery of a spectacular flash of optical and ultraviolet (UV) light accompanying a supernova.

Supernovae are incredibly luminous explosions that occur when a white-dwarf star reaches the end of its lifespan. This latest supernova was of the Type 1A category, which occurs when a small, dense white-dwarf star explodes.

These events are used to measure distances in the universe and determine its rate of expansion. Type 1a supernovae also offer insights into the formation of heavy elements such as iron and how newly formed material is ejected at high velocities out into the universe and used to form the next generations of stars and planets.

The discovery was made using the Zwicky Transient Facility (ZTF) in California in December last year, just a day after the supernova exploded. This event, dubbed SN2019yvq, occurred in a nearby galaxy approximately 140m light years from Earth, close to the tail of the dragon-shaped Draco constellation.

Image of the supernova exploding against a starry background.

ZTF composite image of the supernova (blue dot in the centre of the image) in the host galaxy. Image: ZTF/A A Miller (Northwestern) and D Goldstein (Caltech)

‘Some unusual physics’ going on

After the ZTF spotted the unusual flash, astrophysicists used NASA’s Neil Gehrels Swift Observatory to determine that it was a very hot explosion due to how luminous the UV light was.

“Sky surveys in the past decades have discovered many Type 1a supernovae and the vast majority are very well behaved,” said Kate Maguire, assistant professor in TCD’s School of Physics and a member of the research team.

“What’s very unusual here is the optical and UV flash that lasted just a few days. Analysis of this signal can be used to provide key insights into how exactly the star exploded.”

Dr Mark Magee, also of TCD, said that the incredible heat from the explosion means “some unusual physics” must be occurring, such as the detonation of helium on the star’s surface or hot clumps of iron producing gamma rays.

“Once we know what caused the explosion, we can learn more about the birthplace of heavy elements such as iron,” Magee said.

“Understanding the ways in which a white dwarf explodes gives a more precise understanding of how iron is created and distributed throughout the universe.”

Colm Gorey was a senior journalist with Silicon Republic