Astronomers Discover New Way to Destroy a Star
Astronomers studying a powerful gamma-ray burst (GRB) with the Gemini South telescope, operated by the US National Science Foundation’s (NSF) NOIRLab, have made a groundbreaking discovery. According to a study published in the journal ‘Nature Astronomy’, they may have detected a method of star destruction that has never been seen before.
A Collision in the Crowded Environment
Unlike most GRBs, which are caused by the explosion of massive stars or the random merger of neutron stars, astronomers have concluded that this particular GRB was produced by the collision of stars or stellar debris in the crowded environment surrounding a supermassive black hole at the core of an ancient galaxy.
The Predictable Death of Stars
Most stars in the Universe die in a predictable manner based on their mass. Similar to our Sun, relatively low mass stars shed their outer layers as they age and eventually fade to white dwarfs.
A Fourth Option Revealed
The most massive stars burn the hottest and die sooner in cataclysmic supernova explosions, giving rise to ultradense objects like neutron stars and black holes. However, new research suggests a fourth option that has long been hypothesized but never observed before. If two of these stellar remnants form a binary system, they can also collide.
Evidence of a Collision
Astronomers using the Gemini South telescope, along with other telescopes, have discovered evidence of a collision of stars or stellar debris similar to a demolition in the chaotic and dense region near the supermassive black hole of an ancient galaxy. This finding emerged during the search for the origins of a long-duration gamma-ray burst (GRB).
Understanding the Death of Stars
Andrew Levan, an astronomer at Radboud University in the Netherlands and lead author of the study, expressed excitement about these new results. He stated, “These findings provide insight into how stars meet their end in some of the densest regions of the Universe, where collisions can occur. This knowledge is crucial in understanding the death of stars and exploring unexpected sources that could generate detectable gravitational waves on Earth.”
Ancient Galaxies and Stellar Debris
Ancient galaxies have long passed their star formation stage and are unlikely to have many giant stars remaining, which are the primary source of long GRBs. However, their cores are filled with stars and ultra-dense stellar debris, including white dwarfs, neutron stars, and black holes.
A Fusion in the Turbulent Environment
Astronomers have long suspected that in the turbulent environment surrounding a supermassive black hole, it was only a matter of time before two stellar objects collided to produce a GRB. However, evidence of such a fusion has been elusive.
Observations and Conclusions
The first indications of this event were observed on October 19, 2019, when NASA’s Neil Gehrels Swift Observatory detected a bright gamma-ray flash that lasted slightly over a minute. The researchers then used the Gemini South telescope to conduct long-term observations of the GRB’s glow, aiming to gain a better understanding of its origins.
A New Pathway for Stars to Disappear
These observations allowed astronomers to pinpoint the location of the GRB in a region less than 100 light-years from the nucleus of an ancient galaxy, placing it in close proximity to the galaxy’s supermassive black hole. Interestingly, no evidence of a corresponding supernova, which would have been detected by Gemini South, was found.
Andrew Levan explains, “Our follow-up observation indicated that, instead of the collapse of a massive star, the outburst was most likely due to the merger of two compact objects. By determining its location at the center of a previously identified ancient galaxy, we obtained the first tantalizing evidence of a new pathway for stars to disappear.”
An Uncommon Occurrence
In normal galactic environments, the production of long GRBs from colliding stellar remnants, such as neutron stars and black holes, is extremely rare. However, the nuclei of ancient galaxies are far from ordinary, with millions of stars crammed into a region only a few light-years across.