When a neutron star explodes, gold is created on a massive scale

Powerful magnetar flare reveals unexpected source of gold and platinum, offers solution to 20-year-old mystery

In a groundbreaking study, scientists have linked a mysterious signal from 2004 to a powerful outburst by a magnetar—a neutron star with an extremely strong magnetic field—that produced vast quantities of heavy elements, including gold and platinum, possibly accounting for about 10 percent of the supply of these elements in our galaxy. The discovery challenges the assumption that only neutron star collisions can produce such elements, and raises new mysteries about millions of stellar “factory factories” yet to be discovered.

Mortals have finally been given a rare hint of a new factory for producing heavy elements: a giant flare from a magnetar—a neutron star with a magnetic field trillions of times stronger than Earth’s. Models of the amount of material produced suggest that such eruptions could account for up to 10 percent of the global supply of gold and platinum.

The mystery begins with a bright explosion detected in December 2004 by a space telescope: the magnetar released light waves and particle radiation with an intensity equal to what the Sun produces in a million years. Although the main flare was quickly detected, another faint signal detected about ten minutes later remained unexplained – until the current study.

A team of researchers at the Center for Computational Astrophysics at the Flatron Institute in New York recently deciphered that the second letter indicates the creation of heavy elements, including gold and platinum. According to their calculations, the 2004 flare produced a mass of heavy elements about half the mass of Earth. The paper, published April 29 in The Astrophysical Journal Letters, is only the second ever documentation of the direct creation of these elements: the first was in the collision of two neutron stars in 2017.

“This is only the second time we’ve seen direct evidence of where these elements are formed,” says Brian Metzger, a senior scientist at the center and a faculty member at Columbia University. “This is a significant leap in understanding the formation of heavy elements.”

The elements around us weren’t always in their right places: hydrogen, helium, and some lithium were created in the Big Bang, but almost all the other elements were created inside stars during their lives or violent deaths. Elements heavier than iron are created by the “rapid neutron capture” (r-process) process, which occurs only in extreme environments with an excess of free neutrons. Until now, scientists have assumed that the main r-process sites are supernovae and neutron star collisions.

Observations from 2017 demonstrated that the collision of two neutron stars creates a suitable r-process environment, but the low event density was not enough to account for all the heavy elements in the galaxy. Even then, it was hypothesized that magnetars might make a significant contribution.

How magnetar flares create heavy metals

In 2024, Metzger and his colleagues calculated that giant flares could eject material from the magnetar’s crust into space, where r-process reactions would be possible to produce heavy elements. “It’s amazing to think that some of the precious metals that are in our phones and computers were formed under such extreme conditions,” says Anirudh Patel, a doctoral student at Columbia University and lead author of the new study.

The models show that the flare produces heavy radioactive nuclei whose decay leads to stable elements such as gold, and to the emission of a corona of gamma rays that made it possible – in retrospect – to identify the process.

A forgotten letter is reinterpreted

In 2024, the researchers also analyzed the additional gamma-ray burst discovered in 2004, and it turned out that it was the radiation created by the decay of radioactive nuclei created by the explosion. “That case was forgotten over the years,” says Metzger, “but our models matched that signal perfectly.”

Based on 2004 data, researchers estimate that the flare produced about 2 million billion–trillion kilograms of heavy elements (about the mass of Mars). This suggests that between 1% and 10% of all r-process elements in our galaxy were created in magnetar flares. The remaining percentage may come from collisions, but with records of only one flare and one collision, it is difficult to determine an exact distribution.

The connection to early galactic history

“What is intriguing is that such giant flares can happen early in galactic history,” adds Patel. “They may explain why young galaxies contain more heavy elements than neutron star collisions alone would produce.”

Future observations by dedicated telescopes, such as NASA's Compton Spectrometer and Imager, which will launch in 2027, will help capture more flares in real time. However, confirming the r-process requires pointing an ultraviolet telescope at the source within 10–15 minutes of detecting the gamma rays—a scientific challenge that requires immediate response.

for the scientific article