Atoms that have travelled to Earth from a distant, exploded star have been discovered for the first time, scientists claim.

The radioactive iron-60 atoms were recovered from ocean sediment on a seafloor site in the South Pacific. German astronomers believe they came to Earth from a supernova, one of nature's grandest spectacles.

When a single star explodes, it can outshine an entire galaxy of suns for several days. It becomes brighter than a hundred thousand million stars and light from the explosion can still be detected on Earth even if the explosion is right on the edge of the known Universe.

Scientists are seeing supernovae all the time - they have become useful tools for measuring the size of the Universe. On one occasion, rare and ghostly particles called neutrinos have even been detected from a supernova.

However, finding atoms that have been ejected in the explosion is a little controversial. In a sense, all the atoms on Earth, with the exception of hydrogen and helium, have been processed through, or created in, supernovae many millions - even billions - of years ago. Without supernovae there would be no heavier elements in the Universe.

Close event

But the German team, from Technische Universität München and the Max-Plank Institute, say the iron-60 atoms were deposited on Earth relatively recently - only a few million years ago.

Several sediment layers in the South Pacific were dated, and the samples looked at with a device called an accelerator mass spectroscope that can detect faint traces of iron isotopes.

Because Iron-60 decays by half every 1.5 million years, the levels detected in the sample, and the lack of terrestrial sources of the isotope point to a relatively nearby and recent supernova as its source, the researchers say.

They think the supernova may have been just 90-180 light years from the Earth.