NEWS
F
or our Australopithecus ancestors
who roamed Africa 2.5 million
years ago, the bright new star in
the sky surely would have aroused
curiosity. As luminous as the full
Moon, it would have cast shadows
at night and been visible during the
day. As the supernova faded over
the following months, it probably
also faded from memory. But it left other
traces, now coming to light.
Over the past 2 decades, researchers
have found hundreds of radioactive atoms,
trapped in seafloor minerals, that came
from an ancient explosion marking the
death of a nearby star. Its fusion fuel ex-
hausted, the star had collapsed, generating
a shock wave that blasted away its outer
layers in an expanding ball of gas and dust
so hot that it briefly glowed as bright as
a galaxy—and ultimately showered Earth
with those telltale atoms.
Erupting from hundreds of light-years
away, the flash of x-rays and gamma rays
probably did no harm on Earth. But the
By Daniel Clery
FEATURES
STARSTRUCK
SCIENCE sciencemag.org 16 JULY 2021 • VOL 373 ISSUE 6552 269
Atomic traces left by nearby supernovae point to ancient assaults on Earth
The Crab nebula
is the remains of a
supernova more than
6000 light-years
away—too far to
harm Earth.
PHOTO: NASA; ESA; J. HESTER AND A. LOLL/ARIZONA STATE UNIVERSITY
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