Ever thought about how stars end their life cycle?
Normally, they either shed their layers and become white dwarfs, explode in a supernova, or collide with another star.
However, a group of international scientists may have found a fourth, completely new way that stars can end their lives.
This discovery involves a lot of crashes, a bit like a space demolition derby, and results in a dazzling display of energy known as a gamma-ray burst (GRB).
Gamma-ray bursts are some of the brightest events in the universe. They usually come from exploding massive stars or when two stars merge.
But this new study suggests that GRB 191019A, a specific gamma-ray burst, could be the result of a stellar crash in the super dense area surrounding a gigantic black hole at the heart of an ancient galaxy.
This is a type of event that scientists have speculated about for a long time, but never seen until now.
Wen-fai Fong, a Northwestern University astrophysicist and one of the authors of the study, mentions that unusual events like this one can tell us a lot about the mind-blowing variety of explosions that occur in the universe.
Another researcher, Giacomo Fragione, calls the discovery “undeniably exciting.”
According to the scientists, ancient galaxies, although not actively forming stars, are packed with various stellar remnants such as white dwarfs, neutron stars, and black holes.
Scientists have long suspected that within the busy region surrounding a supermassive black hole, a collision of two stellar objects might occur to produce a GRB. Now, they’ve found the first evidence to support this theory.
In October 2019, a bright flash of gamma rays lasting just over one minute was detected by NASA’s Neil Gehrels Swift Observatory.
Typically, any GRB that lasts longer than two seconds is considered “long.” Long GRBs usually result from the collapse of stars at least 10 times the mass of our Sun.
The scientists used the Gemini South telescope in Chile to observe the fading light left by the GRB. This helped them locate the GRB near the core of an ancient galaxy. What’s even more curious is that they found no evidence of a corresponding supernova, which is often linked with long GRBs.
The researchers believe that the ancient galaxy cores might be so densely packed with stars that occasional collisions are possible, especially given the gravitational pull from a supermassive black hole. These collisions can create enormous explosions visible from vast distances in the universe.
This finding is interesting because it defies what scientists know about the environments that produce both short and long GRBs. It’s possible that similar events are happening elsewhere in the universe, but are hard to detect due to the dust and gas surrounding galactic centers.
Looking ahead, the team hopes to discover more of these events and match them with detections of gravitational waves, ripples in space and time, which would reveal more about their nature.
They are eagerly awaiting the completion of the Vera C. Rubin Observatory, expected to be operational in 2025, which will greatly aid this kind of research.
The study, called “A long-duration gamma-ray burst of dynamical origin from the nucleus of an ancient galaxy,” is published in the journal Nature Astronomy.
