On August 29, 2019, scientists worldwide were alerted to an intense event in space that happened about 1 billion light-years away. While a billion light-years is a massive distance, it is surprisingly close to a cosmic scale, considering the event was an incredibly intense gamma-ray burst. Despite the vast distance away, the gamma-ray burst labeled GRB 190829A happened closer to earth than any other similar event in history.
On a cosmic scale, the burst was so close that scientists considered it a front-row seat to the death of a star in the burst of energy produced as it died. Researchers Sylvia Zhu is a co-author on the new study and said that gamma-ray bursts create bright x-ray and gamma-ray flashes observed in the sky. These are the biggest explosions in the universe and are associated with the collapse of a rapidly rotating massive star to a black hole.
Only a fraction of the liberated gravitational energy feeds the production of an ultrarelativistic blast wave. Zhu says the emission is divided into two specific phases, with an initial chaotic phase lasting tens of seconds followed by a long-lasting but smoothly fading afterglow phase.
It’s during the afterglow phase that scientists have the best opportunity to observe the events because the actual burst happens so fast that it’s difficult to observe in detail. Researchers gathered information on the event from around the planet from various observatories. The team was able to determine that GRB 190829A’s spectrum up to an energy of 3.3 tera-electronvolts. That’s about a trillion times as energetic as photons of visible light.
Researchers say the exceptional aspect of this particular gamma-ray burst was that it happened in our cosmic backyard. The very-high-energy photons weren’t absorbed in collisions with background light on their way to Earth.