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KILONOVA - when stars collide? -
Astronomers have witnessed the titanic collision between two neutron
stars that resulted in the birth of the smallest black hole ever seen and
forged precious metals like gold, silver, and uranium. For the first time, we see the creation of
atoms; we can measure the temperature of the matter and see the microphysics in
this remote explosion.
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--------------------------------------------- 4605 - KILONOVA - when stars collide?
- This violent and powerful collision occurred
130 million light-years away from us in the galaxy “NGC 4993”. It will hopefully paint a picture of the
"past, present, and future" of the mergers of these dense dead stars.
This could reveal the origins of elements heavier than iron, which can't be
forged in even the most massive stars.
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- The collision and merger of the neutron
stars results in a powerful blast of light called a "kilonova." As
the wreckage of this event expands at nearly the speed of light, the kilonova
illuminates its surroundings with light as bright as hundreds of millions of
suns.
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- We can now see the moment where atomic
nuclei and electrons are uniting in the afterglow. For the first time, we see
the creation of atoms, we can measure the temperature of the matter, and we can
see the microphysics in this remote explosion.
We see before, during, and after the moment of birth of the atoms.
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- The gold in your jewelry came from the
universe's most violents events.
Neutron stars are born when stars at least 8 times as massive as the sun
exhaust their fuel for nuclear fusion and can no longer support themselves
against their own gravity. They collapse
and explode.
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- The outer layers of these stars are blasted
away in supernova explosions, leaving a stellar remnant with a mass equal to
between 1 and 2 suns crushed into a diameter of around 12 miles.
The collapse of the core
forces electrons and protons together, creating a sea of particles called
neutrons. This material is so dense that a mere sugar cube's worth of neutron
star matter would weigh 1 billion tons if brought to Earth. That's about the same
as cramming 150,000,000 elephants into the same space that a sugar cube
occupies.
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- It is probably no surprise that this extreme
and exotic matter plays a key role in creating elements heavier than iron.
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- Neutron stars don't always live in
isolation. Some of these dead stars occupy binary systems along with a
companion living star. In rare instances, this companion star is also massive
enough to create a neutron star, and it isn't "kicked away" by the
supernova explosion that creates the first neutron star.
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- The result is a system with two neutron
stars orbiting each other. These objects are so dense that as they swirl around
each other, they generate ripples in spacetime (the four-dimensional
unification of space and time) called “gravitational waves” that ripple through
space, carrying away angular momentum.
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- As the system loses angular momentum, the
orbit of the neutron stars tightens, meaning that the neutron stars move closer
to each other. This results in gravitational waves rippling away faster and
faster, carrying away more and more angular momentum.
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- This situation ends when neutron stars are
close enough for their immense gravity to take over and drag these extremely
dense dead stars together to collide and merge.
This collision sprays out neutron-rich matter with temperatures of many
billions of degrees, thousands of times hotter than the sun. These temperatures
are so hot that they are similar to those of the rapidly inflating universe
just one second after the Big Bang.
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- Ejected particles like electrons and
neutrons dance around the body, the colliding neutron stars, which rapidly
collapse to form a “black hole” in a fog of plasma that cools over the next few
days.
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- Atoms in this cooling cloud of plasma
quickly grab free neutrons the rapid
neutron capture process (r-process) and also ensnare free electrons. This
creates very heavy but unstable particles that rapidly decay. This decay
releases the light that astronomers see as kilonovas, but it also creates
lighter elements that are still heavier than iron, like gold, silver and
uranium.
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- This team saw the afterglow of particles
being snatched to forge heavy elements like Strontium and Yttrium, reasoning
that other heavy elements were undoubtedly created in the aftermath of this
neutron star collision.
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- The matter expands so fast and gains in size
so rapidly, to the extent where it takes hours for the light to travel across
the explosion. This is why, just by
observing the remote end of the fireball, we can see further back in the
history of the explosion. Closer to us, the electrons have hooked to atomic
nuclei, but on the other side, on the far side of the newborn black hole, the
'present' is still just the future.
Think about that!
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- The team's results wouldn't have been
possible without the collaboration of telescopes across the globe and
beyond. This astrophysical explosion
develops dramatically hour by hour, so no single telescope can follow its
entire story. The viewing angle of the individual telescopes to the event is
blocked by the rotation of the Earth.
But by combining the existing measurements from Australia, South Africa,
and the Hubble Space Telescope, we can follow its development in great detail.
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November 11, 2024 KILONOVA - when
stars collide? 4605
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--------------------- --- Monday, November 11,
2024
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