Neutron stars are the remnants of
Super novas and in this case we have one that is far larger than theory allows
unless we are able to accommodate the partner star in an explanatory model.
My quick guess is that the adjacent
star reinforced gravity to produce an ignition point at a much larger radius.
That then ripped the remaining material away to produce a much larger neutron
star.
It is clear that such a trigger
point is not at the center anyway.
Probing the Origins of Extreme Neutron Stars
by Staff Writers
Neutron stars are
the unimaginably dense corpses of what were once much more massive stars that
died while being ripped apart in a supernova explosion. Their average density
is typically more than one billion tons per teaspoonful, even denser than the
nucleus of an atom that is composed of protons and neutrons.
Because these densities can never be reproduced on the Earth, these
objects are great extraterrestrial laboratories for the study of how matter and
exotic particles behave under extreme conditions.
Their existence was predicted in 1934 just one year after the discovery
of the neutron, but it took another 30 years before the first neutron star was
actually observed. Since that time, nearly all of the neutron stars that have
had their masses accurately measured fall in a narrow range centered
approximately on 1.4 times the mass of the Sun.
Last October a group of astronomers using
the Green Bank Radio Telescope found a neutron star that has a mass of nearly
twice that of the Sun. The measurement of the mass is extremely precise because
the neutron star is actually a pulsar (PSR J1614-2230) that spins on its axis
at 317 times per second with clock-like regularity.
What makes this discovery so remarkable is that the existence of a very
massive neutron star allows astrophysicists to rule out a wide variety of
theoretical models that claim that the neutron star could be composed of exotic
subatomic particles such as hyperons or condensates of kaons.
One of the big questions that arises is "how does Nature produce
these very massive neutron stars?" Are they born that way or did they grow
because they gravitationally strip mass from a nearby star? One of the clues to
the origin of this pulsar is that it is not alone. It is found in a very close
9-day binary orbit with another dead star known as a white dwarf.
According to Professor Lorne Nelson (Bishop's University) and his
colleagues at MIT, Oxford, and UCSB, the neutron star was likely spun up to
become a fast-rotating (millisecond) pulsar as a result of the neutron star
having cannibalized its stellar companion many millions of years ago, leaving
behind a dead core composed mostly of carbon and oxygen.
According to Nelson, "Although it is common to find a high
fraction of stars in binary systems, it is rare for them to be close enough so
that one star can strip off mass from its companion star.
But when this happens, it is spectacular."
In order to understand how this binary formed, their strategy was to
compute a grid of theoretical models that would describe how binary systems
evolve over the entire lifetime of the Universe. Thanks to the incredible
number-crunching power of supercomputers, Nelson and his collaborators were
able to calculate the evolution of more than 40,000 plausible starting cases
for the binary and determine which ones were relevant.
As they describe at this week's CASCA meeting in Ontario, Canada, they
found several cases where the neutron star could grow significantly in mass at
the expense of its companion, but as Nelson says, "It isn't easy for
Nature to make such high-mass neutron stars, and this probably explains why
they are so rare."
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