Earth’s
Heavy Metals Result of Supernova Explosion, Researcher Discovers
University
of Guelph
Waterloo
University of Guelph, June 13,
2019 -- That
gold on your ring finger is stellar – and not just in a complimentary way.
In a finding that may overthrow our understanding
of where Earth’s heavy elements such as gold and platinum come from, new
research by a
Some 80 per cent of the heavy elements in the
universe likely formed in collapsars, a rare but heavy element-rich form of
supernova explosion from the gravitational collapse of old, massive stars
typically 30 times as weighty as our sun, said physics professor Daniel Siegel.
That finding overturns the widely held belief that
these elements mostly come from collisions between neutron stars or between a
neutron star and a black hole, said Siegel.
His paper co-authored with Columbia University
The research received coverage on CNET
and
ScienceAlert.
Using supercomputers, the trio simulated the
dynamics of collapsars, or old stars whose gravity causes them to implode and
form black holes.
Under their model, massive, rapidly spinning
collapsars eject heavy elements whose amounts and distribution are
“astonishingly similar to what we observe in our solar system,” said Siegel. He
joined U of G this month and is also appointed to the Perimeter Institute for
Theoretical Physics, in
Most of the elements found in nature were created
in nuclear reactions in stars and ultimately expelled in huge stellar
explosions.
Heavy elements found on Earth and elsewhere in the
universe from long-ago explosions range from gold and platinum, to uranium and
plutonium used in nuclear reactors, to more exotic chemical elements such as
neodymium found in consumer items such as electronics.
Until now, scientists thought that these elements
were cooked up mostly in stellar smashups involving neutron stars or black
holes, as in a collision of two neutron stars observed by Earth-bound detectors
that made headlines in 2017.
Ironically, said Siegel, his team began working to
understand the physics of that merger before their simulations pointed toward
collapsars as a heavy element birth chamber. “Our research on neutron star
mergers has led us to believe that the birth of black holes in a very different
type of stellar explosion might produce even more gold than neutron star
mergers.”
What collapsars lack in frequency, they make up for
in generation of heavy elements, said Siegel. Collapsars also produce intense
flashes of gamma rays.
“Eighty per cent of these heavy elements we see
should come from collapsars. Collapsars are fairly rare in occurrences of
supernovae, even more rare than neutron star mergers – but the amount of
material that they eject into space is much higher than that from neutron star
mergers.”
The team now hopes to see its theoretical model
validated by observations. Siegel said infrared instruments such as those on
the James Webb Space Telescope, set for launch in 2021, should be able to
detect telltale radiation pointing to heavy elements from a collapsar in a
far-distant galaxy.
“That would be a clear signature,” he said, adding
that astronomers might also detect evidence of collapsars by looking at amounts
and distribution of heavy element s in other stars across our Milky Way galaxy.
Siegel said this research may yield clues about how
our galaxy began.
“Trying to nail down where heavy elements come from
may help us understand how the galaxy was chemically assembled and how the
galaxy formed. This may actually help solve some big questions in cosmology as
heavy elements are a nice tracer.”
This year marks the 150th anniversary of
Dmitri Mendeleev’s creation of the periodic table of the chemical elements.
Since then, scientists have added many more elements to the periodic table, a
staple of science textbooks and classrooms worldwide.
Referring to the Russian chemist, Siegel said, “We
know many more elements that he didn’t. What’s fascinating and surprising is
that, after 150 years of studying the fundamental building blocks of nature, we
still don’t quite understand how the universe creates a big fraction of the
elements in the periodic table.”
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