They detect a powerful gamma-ray burst that could be a never-before-seen way to destroy a star

June 23 (EIROPA PRESS) –

astronomers who study a powerful gamma-ray burst (GRB) with the Gemini South telescope, operated by the NOIRLab of the National Science Foundation (NSF) of the United States, they may have detected a never-before-seen way to destroy a staras published in the journal ‘Nature Astronomy’.

Unlike most GRBs, caused by the explosion of massive stars or the random merger of neutron stars, astronomers have concluded that this 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.

Most of the stars in the Universe die in a predictable way, depending on their mass.. Relatively low-mass stars, like our Sun, shed their outer layers as they age, eventually fading to white dwarfs.

The most massive stars burn hottest and die sooner in cataclysmic supernova explosions, creating ultradense objects like neutron stars and black holes. If two of these stellar remnants form a binary system, they too can end up colliding. However, new research points to a fourth option, long hypothesized but never seen before.

In searching for the origins of a long-duration gamma-ray burst (GRB), astronomers using the Gemini South telescope in Chile, part of the Gemini International Observatory operated by NSF’s NOIRLab, and other telescopes, have uncovered 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.

According to andrew levanan astronomer at Radboud University, The Netherlands, and lead author, “These new results show that stars can meet their end in some of the densest regions of the Universe, where they can be pushed into colliding. 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.“, Add.

Ancient galaxies are long past their star formation stage and would have few, if any, giant stars left, which are the main source of long GRBs. However, their cores are packed with stars and ultra-dense stellar debris, such as white dwarfs, neutron stars, and black holes.

Astronomers have long suspected that in the turbulent hive of activity surrounding a supermassive black hole, it would only be a matter of time before two stellar objects collide to produce a GRB. However, evidence for this type of fusion has been elusive.

The first indications that such an event had occurred were observed on October 19, 2019, when NASA’s Neil Gehrels Swift Observatory detected a bright gamma-ray flash that lasted just over a minute. Any GRB that lasts longer than two seconds is considered “long”. Such outbursts typically come from the supernova death of stars at least 10 times the mass of our Sun – but not always.

The researchers then used Gemini South to make long-term observations of the GRB’s glow to better understand its origins. The observations allowed astronomers to locate the GRB in a region less than 100 light-years from the nucleus of an ancient galaxy, placing it very close to the galaxy’s supermassive black hole. The researchers also found no indication of a corresponding supernova, which would leave its mark on the light studied by Gemini South.

“Our follow-up observation told us that rather than the collapse of a massive star, the outburst was most likely due to the merger of two compact objects,” Levan explains. 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.“.

In normal galactic environments, the production of long GRBs from colliding stellar remnants such as neutron stars and black holes is thought to be extremely rare. However, the nuclei of ancient galaxies are anything but normal, and there may be a million or more stars crammed into a region only a few light-years across.

This extreme population density may be great enough for occasional stellar collisions to occur, especially under the titanic gravitational influence of a supermassive black hole, which would perturb the motion of stars and hurl them in random directions. In the end, these stars would intersect and merge, triggering a titanic explosion that could be observed from great cosmic distances.

It is possible that such events occur routinely in similarly crowded regions of the Universe, but have gone unnoticed until now. One possible reason is that the galactic centers are packed with dust and gas, which could obscure both the GRB’s initial flash and the resulting afterglow. This particular GRB, identified as GRB 191019A, may be a rare exception that allows astronomers to detect the outburst and study its subsequent effects.

Researchers would like to discover more such phenomena. Their hope is to pair the detection of a GRB with the corresponding detection of gravitational waves, which would reveal more about its true nature and confirm its origins, even in the murkiest of environments. The Vera C. Rubin Observatory, when it becomes operational in 2025, will be invaluable for this type of research.

“Studying gamma-ray bursts like this is a great example of how the field is advancing thanks to many facilities working together.from detection of the GRB to discoveries of afterglows and distances with telescopes like Gemini, to detailed dissection of events with observations across the entire electromagnetic spectrum,” says Levan.

“These observations add to Gemini’s rich heritage in developing our understanding of stellar evolution,” said Martin Still, NSF program manager for the Gemini International Observatory. The time-sensitive observations are a testament to Gemini’s agile operations and its sensitivity to distant and dynamic events throughout the Universe.“.