Brightest Gamma-Ray Burst Turns Out To Be Normal Supernova, Does Not Produce Heavy Elements From Atomic Nuclei

In October 2022, surveys that monitor the skies for space explosions detected the most enormous burst of gamma radiation ever recorded. Formally known as GRB 221009A, the event clocked in at a record 18 teraelectronvolts 2.4 billion light-years away. The burst was so powerful that it shook our planet's outer atmosphere.

The event is also nicknamed Brightest of All Time (BOAT). Astronomers later determined it to be the birth of a black hole from the violent death of a massive star.

What Are Gamma-Ray Bursts?

Gamma-ray bursts (GRBs) are considered the most powerful explosions observed in the universe. As the name suggests, they are bursts of gamma radiation-the most energetic light in the cosmos. GRBs can erupt in 10 seconds with as much energy as the Sun will emit in 10 billion years.

Scientists know at least two significant events which can lead to the creation of gamma-ray bursts. These include the formation of a black hole when a massive star becomes a supernova or the hypernova accompanying the merger of two neutron stars.

Experts also believe that the kinds of novae that create gamma-ray bursts are responsible for making heavy elements in the universe. Compared with light ones, however, heavy elements did not exist until stars made them.

Stars mostly form out of the hydrogen gas abundant in the universe, but the atomic nuclei in their cores smash together to produce heavier elements. This tops out at iron since the fusion of iron atoms absorbs more energy than it releases.

Elements heavier than iron can be formed in the violent events of giant cosmic explosions. In the aftermath of neutron star collisions, astronomers have detected elements too heavy to form through core fusion.

Still, there is much that scientists do not know. If they understand which explosions are most likely to produce such elements, they can develop a new tool for exploring how the universe makes objects and events and how common such explosions are.

Surprising Twist

A new study of the evolving light has revealed the complexities of this event, and experts wanted to see if there were signatures of heavy elements in the emitted light. Led by astrophysicist Peter Blanchard from Northwestern University, a research team used the James Webb Space Telescope to look at the light in infrared wavelengths six months after the explosion was first observed.

The team found that GRB 221009A was a surprisingly ordinary event, something not expected by the scientists. The event is not any brighter than previous supernovae and instead looks fairly normal in the context of other star explosions associated with less energetic gamma-ray bursts.

As the enormous burst of gamma-radiation, one might expect that the same collapsing star creating a very energetic and bright gamma-ray burst would also lead to a lively and bright supernova. However, it turns out that is not the case. Instead, they detected an extremely luminous GRB, a typical supernova.

GRB 221009A was likely so bright because the jet of the gamma-ray burst was directed right at Earth. Astronomers did not also observe signatures of the heavy elements, suggesting that extremely energetic gamma-ray bursts like the BOAT do not produce these elements.