Astronomers Detect Violent Cosmic Explosion Which Is Brightest Source of High-energy Light in the Universe

An international team of astronomers have identified the brightest known source of high-energy light in the universe—a violent cosmic explosion which took place in a galaxy seven billion light-years away.

The light was produced by a so-called gamma ray burst (GRB)—the most powerful explosions in the cosmos which occur as a result of cataclysmic events. These can include the collapse of massive stars as supernovae or the merging of neutron stars or black holes.

GRBs produce an initial rapid flash of gamma rays—the most high-energy form of light with the shortest wavelength—which usually lasts for a few seconds or minutes.

This initial burst is typically followed by a longer-lived "afterglow" consisting of longer wavelengths of light—such as X-rays, ultraviolet, optical, infrared, microwave and radio—which can be observed for several minutes, months or even years.

Gamma ray bursts are incredibly powerful events. In fact, a typical GRB event lasting just a few seconds or minutes produces about the same energy as our sun does over the course of its entire multi-billion-year lifecycle. This is why GRBs can be detected across such vast distances.

The latest GRB event (dubbed GRB 190114C) was detected by two space satellites—the Neil Gehrels Swift Observatory and the Fermi Gamma-ray Space Telescope—on January 14, 2019, according to a study published in the journal Nature involving more than 300 scientists from across the globe.

Within 22 seconds of the initial detection, the coordinates of GRB 190114C were shared with astronomers around the world, including operators of the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes in Spain's Canary Islands.

"The telescopes were able to observe the burst within 50 seconds of it appearing in the sky," Razmik Mirzoyan, a spokesperson for MAGIC, said in a statement.

gamma ray burst
Gamma-ray bursts can be triggered by the explosion of a dying, massive star, collapsing into a black hole. From the vicinity of the black hole, powerful jets shoot in opposite directions into space, accelerating electrically charged particles, which in turn interact with magnetic fields and radiation to produce gamma rays. DESY, Science Communication Lab

These observations with the MAGIC telescopes revealed photons—or particles of light—from the afterglow of the GRB with an energy between 0.2 and 1 teraelectron volts (TeV.) According to the researchers, this is the highest energy radiation every detected in a gamma ray burst.

"It's a trillion times more energetic than visible light," Gemma Anderson, one of the authors of the study from the Curtin University division of the International Centre for Radio Astronomy Research in Australia, said in a statement. "It makes GRB 190114C the brightest known source of TeV photons in the universe."

After the initial observations, other telescopes around the world followed up in order to identify the origin of the GRB and determine its other characteristics. This data enabled the researchers to describe the probable mechanism behind the emission.

"We assume a two-stage process," Konstancja Satalecka, another author of the study, told Newsweek. "In the first step fast, electrically charged particles from the explosion cloud are deflected in the strong magnetic fields and emit so-called synchrotron radiation, which is of the same nature as the radiation that can be produced in synchrotrons or other particle accelerators on Earth."

"However, these photons are not able to reach the very high energies observed," she said. "Only in the second step, when they collide with the fast particles that generated them, they are boosted to very high gamma-ray energies."

Gamma ray bursts were first detected in the late 1960s by satellites which were being used to monitor nuclear testing across the planet.