In October 2022, an international team of researchers, including Northwestern University astrophysicists, observed the brightest gamma-ray burst (GRB) ever recorded, GRB 221009A. The phenomenon responsible for this historic burst, dubbed as B.O.A.T. (“brightest of all time”), is now confirmed to be the collapse and subsequent explosion of a massive star. This discovery was made using NASA’s James Webb Space Telescope (JWST). Despite solving one mystery, another has emerged as researchers speculated about the absence of heavy elements like platinum and gold in the newly uncovered supernova. The origin of heavy elements in the universe remains one of astronomy’s biggest open questions.
The research, led by Northwestern’s Peter Blanchard, aims to address how some of the heaviest elements in the universe are formed. Although there were no signatures of heavy elements found in the B.O.A.T., it does not rule out the possibility of other gamma-ray bursts producing these elements. Future observations with JWST will provide more information on whether the B.O.A.T.’s ‘normal’ cousins can generate such heavy elements. Blanchard, a postdoctoral fellow at Northwestern’s Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), led this study with co-authors from various institutions around the world.
The B.O.A.T. was so bright that it saturated gamma-ray detectors globally and was observed to be approximately 2.4 billion light-years away in the constellation Sagitta. The explosion lasted a few hundred seconds, producing some of the highest-energy photons ever recorded by satellites designed to detect gamma rays. Researchers were amazed by this rare astronomical phenomenon, which allowed them to delve into the physics behind it. Blanchard and his team chose to study the GRB and supernova aftermath six months after the initial detection using the JWST to observe its later phases.
Despite the normal brightness of the supernova associated with the B.O.A.T., observations did not reveal any heavy elements, prompting further investigation into the mechanisms that produce elements heavier than iron. While the rapid neutron capture process has been confirmed as a primary mechanism, it is unlikely to account for all heavy elements. Astrophysicists suggest that rapidly spinning, massive stars like the one that generated the B.O.A.T. could also be a source of heavy elements. Additional investigation is needed to uncover why a record-breaking GRB and a ‘normal’ supernova were produced by the same collapsed star.
The brightness of the afterglow following the GRB, as seen through JWST data and combined with ALMA observations, suggests that the relativistic jets produced by the collapsing star may play a role. These jets, if narrow, produce a more focused and brighter beam of light, resembling a flashlight beam casting a narrow column of light rather than a broad one. Future studies of the galaxy where the B.O.A.T. occurred may provide more clues, as its host galaxy has been found to have the lowest metallicity compared to previous GRB host galaxies. The study was supported by NASA and the National Science Foundation, with observations made using the James Webb Space Telescope.
As researchers continue to delve into the mysteries surrounding the B.O.A.T. and its associated supernova, they hope to gain a deeper understanding of the processes that govern the formation of heavy elements in the universe. By studying rare and exceptional events like the B.O.A.T., scientists can uncover valuable insights into the cosmic phenomena that shape our universe and shed light on the fundamental questions that lie at the heart of astrophysics. Future observations and studies using advanced telescopes and technologies will be crucial in unraveling these mysteries and advancing our understanding of the cosmos.