Astronomers have discovered a never-before-seen way of destroying a star.
The revelation came as a team of astronomers were studying a powerful blast from space known as a gamma ray burst.
More explosive science
And the discovery is revealing new secrets about stellar collisions in the most densely populated corners of the Universe.
The team made the discovery using the ground-based Gemini South telescope, one of the most powefrul telescopes on Earth.
Most gamma ray bursts are generated when massive stars explode, or when densely-packed neutron stars collide.
Neutron stars are the incredibly dense remnants of massive stars that have ended their lives in a supernova explosion.
These stellar husks are so compact, a teaspoon of the material would weigh about 10 million tonnes.
But neither of these methods is thought to be responsible for this particular burst.
Instead, astronomers believe this one came from the collision of stars or stellar remnants around a supermassive black hole at the centre of an ancient galaxy.
A new way for a star to die
The manner in which a star dies depends on how massive it is.
Stars like our Sun, which are relatively low-mass, throw off their outer layers in old age and become a white dwarf.
More massive stars burn brighter and die sooner in supernova explosions, leaving behind dense neutron stars and black holes.
If two dense objects like these form a binary system in which they orbit each other, they may also eventually collide.
But a team of astronomers believe they may have found a fourth option.
How the discovery was made
The team were searching for the origins of a long-duration gamma-ray burst and found evidence of a large collision of stars, or stellar remnants, near a supermassive black hole.
"These new results show that stars can meet their demise in some of the densest regions of the Universe where they can be driven to collide," says Andrew Levan, an astronomer with Radboud University in The Netherlands and lead author of a paper Nature Astronomy.
"This is exciting for understanding how stars die and for answering other questions, such as what unexpected sources might create gravitational waves that we could detect on Earth."
While ancient galaxies should have few, if any, remaining giant stars, their cores contain a whole plethora of white dwarfs, neutron stars and black holes.
Hypothetically, it should be inevitable that these objects would eventually collide, but direct evidence had proven elusive.
On 19 October 2019, NASA’s Neil Gehrels Swift Observatory detected a bright flash of gamma rays lasting about a minute.
For a gamma ray burst, that's incredibly long.
Gemini South was then trained on the gamma ray burst's fading afterglow, enabling astronomers to pinpoint its location to a region less than 100 lightyears from the centre of an ancient galaxy.
That placed it very near the galaxy's supermassive black hole.
"Our follow-up observation told us that rather than being a massive star collapsing, the burst was most likely caused by the merger of two compact objects," says Levan.
"By pinpointing its location to the center of a previously identified ancient galaxy, we had the first tantalising evidence of a new pathway for stars to meet their demise."
Now, the team want to find more.
They hope to match a gamma ray burst detection along with the gravitational waves produced as the enormous explosion causes ripples in spacetime.
The Vera C. Rubin Observatory, which is just beginning to scan the skies, will help.
"Studying gamma-ray bursts like these is a great example of how the field is really advanced by many facilities working together, from the detection of the GRB, to the discoveries of afterglows and distances with telescopes like Gemini, through to detailed dissection of events with observations across the electromagnetic spectrum," says Levan.
