- 4413
- NEUTRINO FACTORY
- making stardust particles? - A stardust particle locked in meteorite
holds secrets of a star's explosive death.
These particles are like celestial time capsules, providing a snapshot
into the life of their parent star.
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------------------------- 4413 - NEUTRINO FACTORY - making stardust particles?
- Scientists have discovered a rare stardust
particle that came from the explosive supernova death of a distant star. This
speck is locked within an ancient meteorite.
The grain of dust, though small, can help tell a story of stellar life,
death and rebirth that spans almost the entire 13.8 billion-year history of the
universe.
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- It could also allow scientists to unlock
the secrets of a recently discovered type of star that dies in a unique
supernova explosion. These particles
are “celestial time capsules”, providing a snapshot into the life of their
parent star.
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- Most meteorites are time capsules that tell
scientists what material that was present in the solar system around 4.6
billion years ago, when the sun was just an infant star surrounded by a disk of
gas and dust called a "protoplanetary disk."
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- Overly dense patches of this gas and dust
would have collapsed under their own gravity and continued to accrue material,
ultimately leading to planets like Earth and the creation of the solar system
as we know it today. The material that was left over from planet birth would've
been integrated into asteroids and comets.
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- The early solar system was a violent and
chaotic place. Asteroids and comets would slam into Earth and other planets,
and even smash into each other. Fragments created by this early cosmic
demolition derby would also rain down on our planet; this still happens today
providing a cosmic "fossil record" of the early solar system.
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- Yet, there has always been the possibility
that material sealed up in ancient meteorites could tell a much older story,
one not of creation but of destruction.
When stars that existed before the sun died in massive supernova
explosions, the material these stellar bodies had been forging over the course
of their lives would've been spread all throughout the universe.
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- Some of this matter inevitably found its way
into the next generation of stars, and the protoplanetary disks around them.
Distinguishing that hand-me-down material, however, from other types of cosmic
material by looking for uncommon versions, or "isotopes," of familiar
chemical elements.
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- Material created in our solar system has predictable
ratios of isotopes which are variants of elements with different numbers of
neutrons. The particle that they
analyzed has a ratio of magnesium isotopes that is distinct from anything in
our solar system.
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- The results were literally off the
charts. The most extreme magnesium
isotopic ratio from previous studies of pre-solar grains was about 1,200. The
grain in our study has a value of 3,025, which is the highest ever discovered.
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- This exceptionally high isotopic ratio
indicates the star that sent this grain spiraling into the region of space that
would one day host the solar system died in a recently discovered event: A
hydrogen-burning supernova.
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- Hydrogen-burning supernovas occur when
massive stars with leftover hydrogen in their outer layer (after their hydrogen
supplies are exhausted in their cores) explode. This results in the rapid
burning of this remaining hydrogen.
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- Hydrogen-burning supernova is a type of star
that has only been discovered recently, around the same time as we were
analyzing the tiny dust particle. These
findings show how rare particles in meteorites can grant scientists an insight
into events that happen well beyond the limit of the solar system.
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- Neutrino interactions would open the door to
strange new physics beyond the Standard Model. Physicists have made a leap forward in
understanding how these ghostly particles might interact with each other. They are modeling how neutrinos escaping into
space from exploding stars flow like a high-speed liquid.
- Such interactions between neutrinos could
have implications for understanding the Big Bang as well as physics beyond the
Standard Model. However, to confirm how these elusive interactions take place,
astronomers will need to wait for the next supernova in our Milky Way galaxy.
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- Of all the particles in the Standard Model
of physics, neutrinos are the ones scientists know the least about. They have
very tiny masses, barely interact with normal matter, can spontaneously change
identity from one type of neutrino to another and are ubiquitous throughout the
universe. There are trillions of
neutrinos passing through your body right now.
-
- Neutrinos are also difficult to detect. It
would take a bar of lead a light-year long to stop just half of the neutrinos
that pass through you. They interact with matter so infrequently that the
world’s leading neutrino detector, the IceCube Neutrino Observatory at the
South Pole, detects just 275 neutrinos on average per day.
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- Sometimes, though, there’s an upsurge in
neutrinos, example, from a nearby supernova. The closest observed supernova in
over 400 years was SN 1987A, in the Large Magellanic Cloud, a satellite galaxy
of our Milky Way. It is estimated to have produced an incredible 10^58
neutrinos, but detectors on Earth only observed 25 of them.
-
- Nevertheless, researchers from Ohio State
University have now harnessed those
25 detections to investigate the mysterious
possibility that neutrinos are able to interact with each other.
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- According to the Standard Model, neutrinos
should be able to interact with each other. Such interactions could have huge
consequences, helping to explain, among other things, the origin of the masses
of neutrinos, why there are so many neutrinos in the universe, how they might
leave an imprint on the cosmic microwave background (CMB) radiation from the
Big Bang, why the universe is lacking antimatter and even how neutrinos might
have assisted in the formation of dark matter in the early universe.
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- This connection comes from a neutrino’s
ability to oscillate into different flavors, usually either electron, lepton
and tau neutrinos, but a fourth form of neutrino referred to as a sterile
neutrino has also been postulated. The sterile neutrino is one possible
candidate for the identity of dark matter. However, so far no experimental
evidence for sterile neutrinos has come to light.
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- “Relativistic hydrodynamics” describes how
particles that are tightly coupled together and act like a liquid behave when
moving at close to the speed of light, which neutrinos do. Acting as a kind of
quasi-liquid in this way would enable the neutrinos to interact with each
other.
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- Under relativistic hydrodynamics, the
neutrinos could "flow" from a supernova in one of two ways. The first
is as a "burst outflow," which is analogous to popping a balloon in
space and the resulting energy pushing out in all directions.
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- The second and thought to be more likely
possibility is as a "wind outflow," which imagines that the energy
escapes from the popping balloon via myriad nozzles, which would produce a more
consistent flow rate of neutrinos. Each type of outflow would produce its own
distinct pattern in the neutrino signal from a supernova.
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- This work is a big step forward in
understanding how neutrinos scatter from an exploding star. Once the exact
mechanism has been identified, physicists will have a better idea of how
neutrinos can interact with each other. To accomplish this, new data will be
required from another nearby supernova, from which the neutrinos could be
tested for both the burst and wind flow mechanisms. The problem is, a visible
supernova in the Milky Way galaxy or one of its satellite neighbors is a rare
thing.
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- Neutrino interactions are also seen as a
gateway to new physics beyond the Standard Model. Stretching our knowledge of
physics into revolutionary new areas is important for physicists who are
looking to explain many of cosmology’s greatest mysteries, including dark
matter, dark energy, the tension in measurements of the expansion of the
universe and the fundamental nature of matter and space-time.
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-
March 29, 2023 NEUTRINO
FACTORY - making stardust particles? 4413
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2024
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