Hominid Ancestors Saw Nearby Supernova As Second Sun
BBC News Online: Sci/Tech
Wednesday, July 7, 1999 Published at 16:11 GMT 17:11 UK
'Star material' recovered from South Pacific
By BBC News Online Science Editor Dr David Whitehouse
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.
But the German team, from Technische Universit�t M�nchen 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
If this is true, our hominid ancestors must have seen it as the brightest
thing in the sky after the Sun. If the supernova had been any closer, it
might even have affected the Earth's climate, possibly causing the
extinction of species and damage to the land and upper layers of the oceans.
*Universe is 12 billion years old (26 May 99�|�Sci/Tech)
*When a star explodes (08 Feb 99�|�Sci/Tech)
*Explosion on the edge of space (18 Dec 98�|�Sci/Tech)
*Supernova Cosmology Project
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