“One of the universe’s overriding mysteries is where heavy elements originate.” — JAMES LAT TIMER
Mass Separator facility to measure the
mass of a pure sample of zinc-82. The
researchers compared this mass with
predictions in various computer simu-
lations and determined that zinc-82 is
probably too light to be stable beneath a
neutron star’s surface. That’s in line with
the most well-supported prediction of
neutron star composition.
A newly formed neutron star (marked
by arrow) sits in the center of the
supernova remnant Cassiopeia A,
about 11,000 light-years away.
Astrophysicists have long looked for
another astronomical process with
enough energy to forge heavier elements
from protons and neutrons.
Lattimer believes this aspect of the
study is not its greatest contribution;
previous experiments had already shown
that the leading model was more accurate
than others. Instead, he is most impressed
by the technique’s potential to pin down
the characteristics of other exotic nuclei
that may exist in neutron stars.
One potential explanation is that
these elements form in the midst of
the extreme heat and energy of supernovas — no neutron stars required. But
simulations show that these explosions
have an insufficient quantity of neutrons. That need for neutrons leads to
a competing idea: that heavy elements
form when two neutron stars collide and
some of their crustal material escapes
34 neutrons in the most common form
of zinc. The challenge was isolating and
measuring the rare isotope, most of
which would decay in less than a second.
At the CERN lab outside Geneva,
Wolf’s team used the On-Line Isotope
Scientists want to create this compositional profile because neutron stars may
be the source of many of the universe’s
heavy elements. Fusion reactions in the
cores of regular stars produce carbon,
oxygen, nitrogen and other elements
essential for life. But the heaviest element that fusion can construct is iron.
To evaluate this possibility, theorists
need to improve models of neutron star
composition. Mass measurements of
heavy atoms like zinc-82, Wolf says, will
help them do that. Then astronomers can
survey the abundances of heavy elements
in various stars and compare them with
predictions of what would be produced
in neutron star collisions.
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Thursday, October 11, 2012 2:03:00 PM
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