The Brightest Explosion Ever Seen: 1,000x More Energy Than Our Sun Has Emitted Throughout Its 4.5 Billion Year Life

Gamma-ray bursts are the most powerful explosions in the Universe, marking the end of a star’s life cycle. One particularly bright explosion, GRB 221009, was recently detected by several space telescopes. A team of scientists led by astronomers from the Cosmic Dawn Center measured the exact distance to the explosion, allowing them to calculate the total energy released: In a span of just five minutes, it released 1,000 times more energy than our Sun emits during its 4.5 billion year lifespan, making it the largest burst of energy ever recorded. detect.

Gamma-ray bursts are the most powerful and brightest events ever to occur in the Universe. Short-lived gamma-ray bursts typically lasting from a tenth of a second to less than an hour, gamma-ray bursts can eclipse entire galaxies in a short period of time. Explosions are thought to be caused by the collapse of massive stars, the collision of neutron stars, or the merger of a neutron star and a black hole.

Although we have known about their existence for 60 years, there is still much to learn about these fascinating facts. They are not just fleeting and occur at random locations in the sky; Gamma rays are also mostly absorbed by our atmosphere, preventing them from being detected from Earth.

Therefore, to detect them, scientists use a gamma-ray space telescope that, when activated, sends automated instant messages to Earth. This allows astronomers to follow the findings with ground-based telescopes, looking for less energetic “afterlights” that normally follow gamma rays.

Overshadowing an entire galaxy

On October 9, 2022, ESA’s INTEGRAL, NASA’s Swift and Fermi satellites, and other space observatories detected the gamma-ray burst, hence the name GRB 221009A. This prompted Daniele Bjørn Malesani, an astronomer at Radboud University in the Netherlands and a scientist affiliated with the Cosmic Dawn Center, to point the Very Large Telescope (VLT) in Chile in the direction of GRB 221009A. .

Using a VLT-mounted X-shooter, the resulting spectra allowed Malesani and his team to measure the exact distance to GRB 221009A. Although the explosion’s host galaxy was found more than two billion light-years away, that makes it one of the closest. In addition, given the safe distance, the team was also able to calculate the total amount of energy released by the explosion. 

The enigmatic gamma-ray bursts 

Gamma-ray bursts were first detected in 1967 by the Vela satellite, which was built to monitor the sky for possible nuclear weapons testing, which would violate the 1963 Nuclear Test Ban Treaty. First thought to have come from nearby sources in our galaxy, space-sensitive observatories revealed in the 1990s that they must have come from far beyond the Milky Way, spreading across the Milky Way. Universe.

The transient nature of the outbursts makes them difficult to study, but since the late 1990s astronomers have also been able to detect their less energetic aftereffects, from X-rays to optical light. study of infrared rays, helping to establish a theory of their origin.

“Gamma-ray bursts are always full of energy, but this one is truly amazing:
In its 290 seconds of existence, GRB 221009A has released about 1,000 times more energy than our Sun emits over its entire 4.5 billion year lifespan,” Malesani said.

In other words, that light for a short period of time is brighter than the combined light of all the hundreds of billions of stars in the Milky Way. As usual, this calculation assumes that GRB 221009A radiates the same amount of energy in all directions. However, it is more likely that the energy is “concentrated” into a narrow beam, in the direction in which we are standing. The total energy is therefore slightly smaller, although still very high.

And anyway, it was the most powerful gamma-ray burst ever detected, 70 times brighter than before. It has even been reported to affect the Earth’s ionosphere. “We theoretically assume such a powerful event only happens once in 10,000 years,” Malesani said. “This makes us wonder if our discovery was just luck or if there’s something we don’t understand about the nature of gamma-ray bursts.” 

Followed up with James Webb 

GRB 221009A has also been monitored at longer wavelengths using the James Webb Space Telescope. These observations were led by Andrew Levan, also at Radboud University, although Malesani and other DAWners were also part of the group.

These observations have allowed astronomers to better characterize the gamma-ray burst. The James Webb telescope is particularly useful because the explosion, by some unfortunate coincidence, lies behind a thick layer of cosmic dust inside the Milky Way. This has nothing to do with the explosion itself, but makes interpreting the result more difficult because it dims the light from the explosion. Webb looked at the mid-infrared halo, which is much less affected by dust, giving more insight into the event.  

But even Webb has shortcomings 

Kasper Heintz, assistant professor at the Center for Cosmic Dawn, was involved in both studies. He explained:
“Gamma-ray bursts like GRB 221009A will explode with a supernova whose light will ‘add’ to the explosion itself. But for this explosion, despite Webb’s huge mirror, he could not find convincing evidence of a bright supernova.

So is the supernova just dimmer than usual or is it completely gone? The jury is still out and there will be more surprises to come from this mysterious once-in-a-lifetime event.

The papers have just been accepted for publication in Astronomy & Astrophysics and Astrophysical Journal Letters respectively.