Scientists have made a groundbreaking discovery that confirms the creation of gold and other heavy elements through the collision of two ultradense neutron stars. This discovery was made by analyzing a gamma-ray burst (GRB), a blast of high-energy radiation, using the James Webb Space Telescope (JWST) and the Hubble Space Telescope. The observations allowed scientists to witness the creation of gold and other heavy elements, shedding light on how these powerful neutron star mergers generate elements heavier than iron.
The GRB, named GRB 230307A, lasted an unusually long 200 seconds and was associated with a kilonova called AT2017gfo. This kilonova occurred as a result of the collision of two neutron stars located 8.3 million light-years away. This discovery challenges previous theories that long GRBs are caused by the collapse of massive stars, rather than neutron star mergers.
The process of creating heavy elements begins in stars, where nuclear fusion occurs and elements like helium, nitrogen, oxygen, and carbon are formed. The most massive stars can forge elements up to iron in their cores. When a stellar core is filled with iron, fusion ceases and the core collapses under its own gravity, resulting in a supernova explosion. This collapse transforms the core into a neutron star, which is an extremely dense object composed mainly of neutrons.
Neutron stars can exist alone or in binary systems with another neutron star. When two neutron stars orbit each other, they emit gravitational waves that cause them to spiral together. Eventually, the two stars collide and merge, creating a gamma-ray burst and releasing a spray of neutron-rich material. This material undergoes a process called rapid-neutron capture, or r-process, where other atomic nuclei capture the free neutrons and become superheavy elements called “lanthanides.” These lanthanides then decay into lighter elements, including gold and silver.
The recent discovery of the kilonova associated with GRB 230307A provided scientists with the opportunity to observe the evolution of a kilonova over a longer period of time. This observation was made possible by the JWST and Hubble, which offered sensitive and multi-color coverage. The observations revealed the recombination of heavy elements, such as lanthanides, during the cooling process of the kilonova.
This discovery confirms that neutron star mergers are responsible for the creation of elements heavier than gold and also suggests that long GRBs can originate from these mergers. However, it has not yet explained why this particular neutron star merger resulted in such a long-duration GRB. Further research and observations are needed to fully understand these events and their implications for nucleosynthesis.
The research team’s findings were published in the journal Nature, and they look forward to future joint observations of long-duration gamma-ray bursts, kilonovas, and gravitational waves to unravel the mysteries surrounding these extraordinary events.
