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ASTRONOMERS WHITNESS BLACK
HOLE? - For the first time, astronomers see the
creation of atoms. They can measure the
temperature of the matter and see the microphysics in this remote
explosion. They 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.
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--------------------------------- 4611
- ASTRONOMERS WHITNESS
BLACK HOLE?
-
- The
astronomers snapshot of this violent and powerful collision, which
occurred 130 million light-years away from us in the galaxy NGC 4993, was
created with a range of instruments, including the Hubble Space Telescope.
-
- 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.
-
- 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.
-
- This remarkable' explosions from
colliding, dead stars could reveal the true expansion rate of the
universe. We can now see the moment
where atomic nuclei and electrons are uniting in the afterglow. 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. 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.
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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
(20 kilometers).
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.
It is probably no surprise
that this extreme and exotic matter plays a key role in creating elements
heavier than iron.
A irregularly shaped near
spherical blue cloud with nodules extending from it
An illustration shows a cloud
of material erupting from a collision of neutron stars (Image credit: NASA
Goddard/CI Lab)
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.
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.
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.
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.
An artist's depiction of
colliding black holes causing ripples in the fabric of space-time.
An artist's depiction of
colliding neutron stars sending out ripples in spacetime called gravitational
waves. (Image credit: R. Hurt/Caltech-JPL)
Ejected particles like
electrons and neutrons dance around the body, birthed by the colliding neutron
stars, which rapidly collapse to form a black hole in a fog of plasma that
cools over the next few days.
Atoms in this cooling cloud of
plasma quickly grab free neutrons via what is called 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.
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.
"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," team member Kasper Heintz, a
researcher at the Niels Bohr Institute, said. "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."
Related Stories:
— A new approach might help
scientists see inside a neutron star
— City-size neutron stars may
actually be bigger than we thought
— The heaviest neutron star
ever observed is shredding its companion
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," team leader and Neils Bohr
Institute researcher Albert Sneppen said in the statement. "But by
combining the existing measurements from Australia, South Africa, and the
Hubble Space Telescope, we can follow its development in great detail."
The team's paper was published
on Wednesday (Oct. 30) in the journal Astronomy & Astrophysics.
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November 16, 2024 4611
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