Pacific Ocean crusts reveal traces of a nearby supernova

A team of German researchers recently detected a sharp anomaly in beryllium-10 (¹⁰Be) within mineral crusts taken from the central and northern Pacific Ocean. Beryllium-10 is a radioactive isotope that forms when cosmic rays strike nitrogen and oxygen atoms high in Earth’s atmosphere. After formation, it drifts downward, mixes with rain, and slowly settles onto the ocean floor, becoming locked into layers of ferromanganese crust.

Under normal conditions, this cosmic-ray “rain” is steady across the globe, resulting in a nearly uniform record of ¹⁰Be deposition. However, the crust samples revealed a pronounced spike between 11.5 and 9.0 million years ago, with a sharp maximum around 10.1 million years ago during the late Miocene epoch. The anomaly’s intensity far exceeded typical variations, suggesting that something abruptly increased the cosmic-ray flux reaching Earth.

Because ¹⁰Be has a half-life of 1.39 million years, its concentration can record events lasting only a few hundred thousand years. Such a brief and intense rise is unlikely to have been caused by gradual geological processes alone. One possible explanation is that a nearby star exploded as a supernova, flooding the Solar System with energetic particles that temporarily enhanced isotope production.

To test the idea, a second international research group used galactic models to trace Earth’s position through the Milky Way at the time of the anomaly. Their results suggest that during the late Miocene, the Solar System was moving through an active star-forming region where massive stars routinely ended their lives in violent explosions.

Gaia data reveals a neighborhood of dying stars

Astrophysicist E. Maconi and colleagues at the University of Vienna turned to the European Space Agency’s Gaia DR3 catalog to reconstruct the motion of the Sun and 2 725 nearby star clusters over the past 20 million years. By integrating their orbits through a model of the Milky Way’s gravitational field, the team identified where potential supernovae might have erupted close to Earth.

They calculated the probability that at least one supernova occurred within 100 parsecs (326 light-years) of the Solar System during the same time window as the beryllium anomaly. The result was striking: a 68 percent chance that a supernova exploded within that distance between 11.5 and 10.1 million years ago.

Nineteen clusters each showed more than a one percent likelihood of producing such an event, but two young clusters stood out. Known as ASCC 20 and OCSN 61, both lie in the Orion star-forming complex, an immense structure of gas and young stars extending roughly 9 000 light-years (2 760 parsecs) along the Radcliffe wave.

According to orbital reconstructions, ASCC 20 approached to within 34 parsecs (111 light-years) of the Sun about 11.8 million years ago, remaining within 100 parsecs for the full duration of the isotope anomaly. The cluster’s age of roughly 22 million years and initial mass of around 500 solar masses suggest that multiple massive stars may have exploded during that time. OCSN 61, slightly younger at about 16 million years, likely added to the supernova rate as it passed within 60 parsecs (196 light-years).

Close encounters, but not extinction-level

Maconi’s analysis found that none of these clusters approached closer than about 20 parsecs (65 light-years), safely beyond the so-called kill radius within which a supernova could strip Earth’s ozone layer or damage its biosphere. Even so, a blast within 50 to 100 parsecs (163 to 326 light-years) could have noticeably increased cosmic radiation at Earth’s surface and boosted ¹⁰Be production in the atmosphere.

Statistical modeling indicated a one percent probability of a supernova within 35 parsecs (114 light-years), rising to 14 percent at 50 parsecs (163 light-years) and 28 percent at 70 parsecs (228 light-years). These distances align closely with the range at which a supernova’s shockwave could influence the Solar System without catastrophic effects.

The researchers also found that the probability of at least one explosion reached 68 percent by 100 parsecs, strongly supporting the plausibility of a nearby cosmic source. While the result does not confirm the exact location or number of explosions, it demonstrates that supernovae in the Orion region remain a realistic cause of the ¹⁰Be anomaly.

Importantly, the study also ruled out direct life-threatening radiation effects. The estimated distances suggest that even a relatively energetic Type II supernova would have primarily affected atmospheric chemistry rather than global ecosystems.

Geological or cosmic? Competing explanations

The supernova hypothesis is not the only explanation. Some geophysicists argue that large-scale oceanic changes could produce similar isotope variations. Around 10 million years ago, the Antarctic Circumpolar Current intensified as global cooling accelerated, possibly redistributing ¹⁰Be-rich sediments in the Pacific.

Alternatively, the anomaly could reflect a temporary collapse of the heliosphere, the magnetic bubble that shields the Solar System from cosmic rays. As the Sun drifted through denser interstellar gas, heliospheric compression might have allowed more cosmic radiation to reach Earth, enhancing isotope production without requiring a nearby explosion.

The anomaly’s broad shape also complicates interpretation. Rather than a sharp spike, the record shows a wide plateau lasting roughly two million years. Diffusion in seafloor crusts, combined with dating uncertainties of about ±0.5 million years, could have smeared what was originally a shorter-lived signal.

Despite these uncertainties, the timing of the anomaly coincides closely with the Solar System’s departure from the Orion star-forming region, suggesting that both astrophysical and terrestrial factors may have contributed to the isotopic event.

Clues from other isotopes

A clear way to confirm a supernova origin would be to detect other cosmic radionuclides from the same period. Isotopes such as iron-60 (⁶⁰Fe) and manganese-53 (⁵³Mn), with half-lives of 2.6 and 3.7 million years respectively, are known products of stellar explosions.

Traces of ⁶⁰Fe have already been discovered in deep-sea crusts and Antarctic snow dating to within the past few million years, confirming that supernovae occurred near Earth more recently. However, no ⁶⁰Fe signal has yet been found corresponding to the 10-million-year-old beryllium event.

That absence could result from isotope decay, uneven global deposition, or incomplete sampling of sediments of that age. Because ⁶⁰Fe decays faster than ¹⁰Be, only a faint residue would remain today. In contrast, ⁵³Mn may provide a more stable tracer if measurable in the same strata.

Future high-precision accelerator mass spectrometry could detect such isotopes, allowing scientists to test whether multiple signals coincide globally. If identical ¹⁰Be peaks appear in other ocean basins or in Antarctic ice cores, it would strongly favor a cosmic rather than geological origin.

The Solar System’s passage through a stormy galaxy

Ten million years ago, the Sun was emerging from the Orion Arm of the Milky Way, moving through a turbulent region shaped by repeated stellar explosions. The resulting chain of supernovae carved out the Local Bubble, a vast cavity roughly 1 000 light-years (305 parsecs) across that still surrounds our Solar System.

Astrophysical models suggest that between 10 and 20 supernovae have occurred in Orion over the past 12 million years. The event that produced the ¹⁰Be anomaly could have been one of the last in that sequence, contributing to the Local Bubble’s expanding shell of hot plasma and dust.

By comparing Gaia’s precise star cluster data with isotope records preserved on Earth, researchers can now reconstruct how the Solar System’s galactic journey has shaped its environment over time. The intersection of astrophysics and geochemistry offers a new window into how distant cosmic events leave tangible marks on our planet.

Further sampling from seafloor archives around the world will be essential to determine whether the anomaly represents a localized Pacific signal or a truly global event. If confirmed, it would stand as the oldest isotopic evidence of a nearby supernova’s impact on Earth’s atmosphere.

References:

¹ The late Miocene ¹⁰Be anomaly and the possibility of a supernova – E. Maconi et al. – Astronomy & Astrophysics – September 23, 2025 – https://doi.org/10.1051/0004-6361/202556253 – OPEN ACCESS

² Mysterious Anomaly in Pacific Ocean Hints at Nearby Supernova Explosion – Science Alert – October 11, 2025

Reet Kaur

I’m a science journalist and researcher at The Watchers, contributing to the Epicenter edition, where I cover peer-reviewed scientific research and emerging discoveries across Earth and space sciences. With a background in astronomy and a passion for environmental science, I’ve worked in shark and coral conservation in Fiji, conducting reef and shark-behavior research, contributing to mangrove restoration, and earning PADI Open Water and Coral Reef Certifications. I bring a blend of scientific rigor and storytelling to illuminate the discoveries shaping our planet and beyond.

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