Kilonova Millions of Times Brighter Than Milky Way Birthed Rarest Elements

In the second-brightest supernova ever seen, two neutron stars have collided and created a variety of rare heavy elements, many of which are needed for life on Earth.

The extraordinarily bright gamma-ray burst created by the collision, named GRB 230307A, is thought to be over a million times brighter than the entire Milky Way Galaxy.

In the huge supernova—also known as a kilonova—caused by the two neutron stars merging, enough energy was released to form heavier elements via the fusion of lighter elements.

Scientists revealed in a paper published in the journal Nature that they discovered the rare heavy chemical element tellurium in the aftermath of the explosion, and therefore expect the presence of elements such as iodine—essential for life as we know it.

Elements can be formed in the hearts of explosions like these via a process known as nucleosynthesis, which is when lighter elements are forced together and fused by the huge amounts of energy released during a supernova or kilonova. This "pressure cooker" environment is how scientists think that all of the heaviest elements in nature, such as gold, platinum and uranium, are formed.

This finding marks only the second time ever that individual heavy elements have been detected in the aftermath of a neutron star merger. The first was in 2019 when strontium was detected following a kilonova caused by the GW170817 neutron star merger.

"Neutron stars are about one and a half times the mass of the sun but crushed down into an area roughly the size of London. That's a lot of material to squeeze into such a small space, so when they collide, there's a lot of energy to come out. The pressures involved during the collision squeezes material out at almost the speed of light – that's the source of the gamma-ray burst we see," Ben Gompertz, an assistant professor of astronomy at the University of Birmingham, and co-author of the study, told Newsweek.

"The main thing you need to create very heavy elements is neutrons. If you fire enough of them at an atom in a short space of time, they will stick faster than they can decay, so very quickly (i.e., within a second or so), your atoms are very massive. We only know of one type of system that has enough pressure and neutrons to create the conditions for this to happen – neutron star mergers," Gompertz said.

"Some processes during the merger can actually break neutrons apart, but the fact we've found a heavy element like tellurium in this merger tells us the conditions were right to make other very heavy elements needed for life."

This kilonova's gamma-ray burst lasted for around 200 seconds and was caught by several telescopes, including NASA's James Webb Space Telescope, Fermi Gamma-ray Space Telescope, and Neil Gehrels Swift Observatory. This is an unusually long burst, as neutron star merger gamma-ray bursts usually only last a few seconds, with longer durations being produced by the explosive death of a massive star.

"Until recently, we didn't think mergers could power gamma-ray bursts for more than two seconds," Gompertz said in a statement. "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."

The James Webb Space Telescope pinpointed the location of the neutron star collision and the kilonova as within a spiral galaxy about a billion light-years away. The two neutron stars are thought to have been ejected from their home galaxy and traveled around 120,000 light-years—around the length of the Milky Way—before merging several hundred million years later.

"We can detect these things mostly because JWST is so powerful, and crucially, can observe in the infra-red. We haven't had a telescope this powerful in that part of the electromagnetic spectrum before—the previous kilonova we saw was about 6x closer, and we caught it early when it was much brighter (because of the gravitational wave signal)," Gompertz said.

The scientists are thrilled by the discoveries of the kilonova and the traces of tellurium, as it takes us one step closer to solving the puzzle of how the elements that we need for life on Earth came to be.

"This is an important next step in our understanding of the role binary neutron star mergers play in terms of populating the periodic table of elements. It complements the breakthrough achieved a few years ago thanks to gravitational wave detections, exploiting the step change that JWST now represents," Danny Steeghs, a professor of astronomy and astrophysics at the University of Warwick, said in the statement.

Lead author of the study Andrew Levan, a professor of Astrophysics at Radboud University in the Netherlands, agreed: "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," he said in the statement.

Do you have a tip on a science story that Newsweek should be covering? Do you have a question about kilonovas? Let us know via science@newsweek.com.

Update 10/26/23, 12:11 p.m. ET: This article was updated with comment from Ben Gompertz.