Every year, a little bit of the cosmos reaches Earth. Not as visible meteorites, but as tiny particles and individual atoms from distant stellar explosions drifting through interstellar space. An international research team led by the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has now found such material in ancient Antarctic ice and traced its origin more precisely. The results were published in the journal Physical Review Letters.
What the researchers were looking for is called iron-60, a rare radioactive form of iron that hardly occurs naturally on Earth. It forms inside massive stars and is hurled into space when these stars explode in a supernova. Iron-60 can therefore only be detected on Earth if it arrived here from space.
A needle in 50,000 soccer stadiums
Detecting the isotope was an extraordinary technical challenge. The team transported around 300 kilograms of ice from the AWI in Bremerhaven to Dresden, where it was chemically processed. In the end, only a few hundred milligrams of dust remained. The actual measurement was carried out at the HIAF facility at Australian National University — currently the only facility in the world capable of detecting such tiny quantities of iron-60. “It’s like looking for a needle in 50,000 soccer stadiums filled to the ceiling with hay. The machine finds the needle in an hour,” explains Annabel Rolofs from University of Bonn.
The findings suggest that the environment around our solar system still contains traces of ancient stellar explosions. “This means that the clouds around the solar system are linked to a stellar explosion. And for the first time, this gives us the opportunity to investigate the origin of these clouds,” says Koll. The researchers are already planning the next step: analyzing even older ice cores from the time before the solar system entered the Local Interstellar Cloud.
Original publication:
D. Koll, A. Rolofs, F. Adolphi, S. Fichter, M. Hoerhold, J. Lachner, S. Pavetich, G. Rugel, S. Tims, F. Wilhelms, S. Zwickel, A. Wallner: Local Interstellar Cloud Structure Imprinted in Antarctic Ice by Supernova 60Fe, Physical Review Letters, 2026.
