2021-09-10 17:51:18
From time to time a fleeting flash of a cataclysm of unimaginable dimensions reaches us from the depths of the Cosmos. The radiation emitted during the burst reaches Earth after traveling billions of years and, despite the time and distance traveled, still has enough energy to be detected by space telescopes specially designed to capture the most energetic waves in the spectrum. electromagnetic: gamma rays.
“The detection of gamma-ray bursts has a funny story,” says Tomás Ahumada, our guest today on Talking to Scientists. The first detections took place in the 1960s, when the United States of America and the extinct Soviet Union were fighting for world control. Both powers carried out an unbridled race in the development of nuclear weapons and, perhaps aware of the danger that this entailed, they decided to sign an agreement that limited nuclear tests. To monitor compliance with the agreements, the United States designed a set of satellites called “VELA” designed to detect the tiny gamma-ray flash that occurs at the time of a nuclear explosion. To everyone’s surprise, the Velas began to detect gamma-ray flashes that were not coming from Earth but from deep space. Thus began what is called “Gamma Ray Astronomy”.
Decades later, as new space telescopes specially designed to capture gamma-ray bursts from the cosmos were launched, the number of detections increased and scientists observed that, based on their duration, they could be divided into two classes. Some of them are true radiation flashes that have a very short duration, less than 2 seconds, they are known as SGRB (Short Gamma Ray Burst). Others last longer, are the so-called LGRB (Large Gamma Ray Burst). This classification has been established because the two types are thought to have different origins. Short bursts (SGRB) are believed to originate from the merger of two neutron stars or a neutron star and a black hole. The long-term (LGRB), instead, have their origin in the sudden collapse of a high-mass star when it exhausts its nuclear fuel.
That was the case until now, however, the study published in Nature Astronomy, led by Tomás Ahumada, a Chilean researcher at the NASA and from the University of Maryland, shows that this division is not as clear as previously thought. The investigation originates on August 26, 2020, at 4:29:52 UTC, when the gamma-ray burst monitor installed on the Fermi space telescope detected a gamma-ray flash GRB200826. The burst was short-lived, just over a second, so it was classified as SGRB. Since Fermi detectors, and gamma ray detectors in general, only provide an approximate location within a more or less wide region of the sky, after detection a thorough investigation is necessary to determine the exact position of the source. To achieve this, Fermi and the concert of instruments of the interplanetary network (IPN) send alert signals to hundreds of scientists who rush to scan the region with X-ray, optical, and radio telescopes to try to locate the glow from the source of the gamma-ray flash. This is how Tomás Ahumada and his team managed to locate the candidate who met all the requirements, he was identified as ZTF20abwysqy.
The origin of the outburst is in a galaxy located more than 6,800 million light years away. After the Fermi telescope alert, Tomás Ahumada and a large group of more than fifty scientists searched for and located the source and studied the curve of light emitted over the hours and days following the explosion. The results revealed that, despite being a short gamma-ray burst (SGRB), its origin is not, as might be expected, the collision of two neutron stars but the result of the gravitational collapse of a supermassive star.
I invite you to listen to Tomás Ahumada, Chilean researcher at the Department of Astronomy, University of Maryland, and at the Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA.
References:
Ahumada, T., Singer, L.P., Anand, S. et al. Discovery and confirmation of the shortest gamma-ray burst from a collapsar. Nat Astron (2021).
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