An international team of researchers, including from the University of Birmingham, UK observed the creation of rare chemicals during a gamma-ray burst, according to a study published in Nature. The authors believe this casts new light on how heavy elements are created.
The scientists observed the bright gamma-ray burst GRB 230307A (which was caused by a neutron star merger) using ground and space-based telescopes, including NASA’s James Webb Space Telescope, Fermi Gamma-ray Space Telescope, and Neil Gehrels Swift Observatory. In the aftermath of the explosion, results revealed the presence of the heavy chemical tellurium. Other elements, including iodine and thorium, are also likely to be amongst the material ejected by the explosion, also known as a kilonova.
“Gamma-ray bursts come from powerful jets travelling at almost the speed of light – in this case, driven by a collision between two neutron stars. These stars spent several billion years spiralling towards one another before colliding to produce the gamma-ray burst we observed in March this year. The merger site is the approximate length of the Milky Way (about 120,000 light-years) outside of their home galaxy, meaning they must have been launched out together,” said Dr Ben Gompertz, Assistant Professor of Astronomy at the University of Birmingham. “Colliding neutron stars provide the conditions needed to synthesise very heavy elements, and the radioactive glow of these new elements powered the kilonova we detected as the blast faded. Kilonovae are extremely rare and very difficult to observe and study, which is why this discovery is so exciting.”
GRB 230307A was one of the brightest gamma-ray bursts ever detected – over a million times brighter than the entire Milky Way Galaxy combined. This is only the second time heavy elements have been detected after the merger of a neutron star, providing valuable clues about how heavy chemicals needed for life are formed.
“Just over 150 years since Dmitri Mendeleev wrote down the periodic table of elements, we are now finally in the position to start filling in those last blanks of understanding where everything was made, thanks to the James Webb Telescope,” said lead author Andrew Levan, Professor of Astrophysics at Radboud University in the Netherlands.
The explosion lasted for about 200 seconds, which is unusual, as gamma-ray bursts usually last less than two seconds. Long gamma-ray bursts like this one are usually caused by the explosive death of a massive star. The researchers now want to learn how these neutron star mergers work and how they can power such long-lasting explosions.
“Just a few short years ago, discoveries like this one would not have been possible, but thanks to the James Webb Space Telescope, we can observe these mergers in exquisite detail,” said Dr Samantha Oates, a co-author of the study.
“Until recently, we didn’t think mergers could power gamma-ray bursts for more than two seconds. Our next job is to find more of these long-lived mergers and develop a better understanding of what drives them – and whether even heavier elements are being created. This discovery has opened the door to a transformative understanding of our universe and how it works,” concluded Dr Gompertz.
Levan, A., Gompertz, B.P., Salafia, O.S. et al. Heavy element production in a compact object merger observed by JWST. Nature (2023). https://doi.org/10.1038/s41586-023-06759-1