Star flares blast out massive amounts of gold across the galaxy

A brilliant flash from deep space once baffled scientists. But now, that mystery has been solved—and it reshapes what we know about the universe’s heaviest elements.

Back in December 2004, a massive eruption from a rare type of star blasted gamma rays toward Earth. That initial flash came from a magnetar, a type of neutron star with an incredibly strong magnetic field. Though it lasted only seconds, the blast released more energy than the Sun will emit over a million years.

But it wasn’t just the short burst that caught attention. About 10 minutes later, a second wave of energy swept across telescopes, forming a smooth gamma-ray glow that faded over the next few hours. At the time, scientists couldn’t explain it. For 20 years, that second signal sat as an open puzzle in astronomy.

Thanks to new research from scientists at the Flatiron Institute’s Center for Computational Astrophysics and Columbia University, that faint afterglow is now known to be something far more exciting. It marked the birth of some of the universe’s rarest materials—heavy elements like gold and platinum.

The production of heavy elements has long fascinated astronomers. Hydrogen, helium, and a bit of lithium were born in the Big Bang, but everything else—carbon in your body, calcium in your bones, iron in your blood—was formed inside stars.

When it comes to even heavier elements like uranium, gold, and platinum, their origin is much rarer. These elements are forged in a process called rapid neutron capture, or the r-process. This occurs when atomic nuclei absorb neutrons so quickly that they can jump to heavy forms before having a chance to decay. But the r-process only happens in extreme places with lots of free neutrons.

For decades, researchers believed these environments were limited to supernovae or the collisions of neutron stars. In 2017, one such collision proved that theory. A neutron star merger observed with gravitational waves created exactly the conditions needed for r-process formation.

But that still didn’t solve the full mystery. These mergers are rare and tend to happen far from star-forming regions. That left scientists wondering how young, metal-poor galaxies could contain so many heavy elements. Clearly, something else had to be contributing.

Now, they know: giant flares from magnetars.

Magnetars are the most magnetized stars in the universe, packing magnetic fields trillions of times stronger than Earth’s. They are born from the cores of massive stars after supernova explosions and live short, violent lives.

Among the most energetic of their events are giant flares. These rare outbursts eject a fireball of matter and radiation. In under a second, they can release as much energy as the Sun does in 100,000 years.

In the case of the 2004 flare from the magnetar SGR 1806–20, a team led by J. Cehula modeled what happened during the explosion. Their simulations showed that the blast sent a shockwave deep into the star’s crust, heating and launching a layer of matter into space at a speed exceeding 10 percent the speed of light.

This debris wasn’t just junk. As it rapidly cooled and expanded, it created the perfect recipe for r-process nucleosynthesis—the formation of those elusive heavy elements.

Even though this ejected material wasn’t highly neutron-rich, it still achieved the right conditions for the r-process through a mechanism called α-rich freeze-out. In this scenario, high entropy and fast expansion reduce the number of seed nuclei. That raises the ratio of neutrons to seeds, allowing heavy nuclei to form.

A separate study by A. Patel and colleagues ran detailed nuclear reaction simulations on this magnetar ejecta. Their calculations confirmed that gold-like and other heavy nuclei could indeed form in this kind of event.

Freshly created r-process elements are unstable. As they decay, they release gamma rays—high-energy light that can be observed if you look in the right place at the right time.

Back in 2004, telescopes like INTEGRAL, Konus-WIND, and RHESSI all saw a delayed gamma-ray signal a few minutes after the initial flare. Scientists didn’t know what to make of it. The burst didn’t pulse like the earlier flare had, and the energy slowly faded over a few hours.

That signal was the glow from radioactive decay of r-process elements.

The new study, published in The Astrophysical Journal Letters, showed that this fading MeV (mega-electron-volt) light fits perfectly with what you’d expect from r-process production. The delayed signal peaked between 600 to 800 seconds after the flare and matched predicted gamma-ray fluences and energy levels. Researchers estimated that about a third of Earth’s mass in heavy elements was created in that single flare.

“That event had kind of been forgotten over the years,” says Brian Metzger, senior research scientist at the Flatiron Institute and Columbia professor. “But we very quickly realized that our model was a perfect fit for it.”

Metzger and Patel’s team estimate that these flares could be responsible for up to 10 percent of the heavy elements in our galaxy. Combined with neutron star mergers, that could account for nearly all the known r-process products observed today.

This discovery doesn’t just answer a lingering mystery; it helps solve a much bigger one. Scientists studying the composition of ancient, low-metallicity stars found more r-process elements than expected. But neutron star mergers, which often take time to occur after star formation, couldn't explain how early galaxies got so rich in these materials.

Magnetar flares, however, can erupt much sooner after a star is born. That means they could enrich their surroundings quickly—just the kind of event needed to explain those ancient observations.

“These giant flares could be the solution to a long-standing problem,” Patel says. “They help explain the high levels of heavy elements we see in young galaxies.”

Yet, there’s still much to learn. With only one observed magnetar flare and one confirmed neutron star merger producing r-process elements, the full picture remains incomplete.

“We can't exclude that there could be third or fourth sites out there,” Metzger says. “This is just the beginning.”

The search for r-process events isn’t over. Astronomers are now working to spot these gamma-ray glows in real time. The key is catching the signal early. The telltale radioactive light peaks just 10 to 15 minutes after a flare—so fast response is critical.

NASA’s upcoming Compton Spectrometer and Imager (COSI), set to launch in 2027, will play a key role. With better sensitivity and spectral resolution, COSI could finally capture the detailed gamma-ray fingerprints of specific radioactive isotopes, confirming r-process formation in real time.

Other MeV-range telescope missions may soon follow, driven by the promising science case this flare provides. Magnetar flares don’t just offer answers—they offer a chase. And scientists are ready.

“It’s pretty incredible to think that some of the heavy elements all around us, like the precious metals in our phones and computers, are produced in these crazy extreme environments,” Patel says.

The universe continues to reveal how its rarest treasures are made—not in peaceful stellar nurseries, but in cosmic violence.

Note: The article above provided above by The Brighter Side of News.

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