- 4249 - COSMIC
RAYS - the highest energy? In 1991, the University of Utah Fly’s Eye
experiment detected the highest-energy cosmic ray ever observed. The “Oh-My-God particle”, cosmic ray’s
energy shocked astrophysicists. Nothing in our galaxy had the power to produce
it, and the particle had more energy than was theoretically possible for cosmic
rays traveling to Earth from other galaxies. Simply put, the particle should
not exist.
-------------------------- 4249 - COSMIC RAYS - the highest energy?-
- The Telescope
Array has since observed more than 30 ultra-high-energy cosmic rays, though
none approaching the Oh-My-God-level energy. No observations have yet revealed
their origin or how they are able to travel to the Earth.
-
- On May 27, 2021,
the Telescope Array experiment detected the second-highest extreme-energy
cosmic ray. At 2.4 x 10^20 eV, the energy of this single subatomic particle is
equivalent to dropping a brick on your toe from waist height.
-
- The Telescope
Array consists of 507 surface detector stations arranged in a square grid that
covers 270 miles^2 outside of Delta, Utah in the state’s West Desert. The event
triggered 23 detectors at the north-west region of the Telescope Array,
splashing across 18.5 mi^2. Its arrival
direction appeared to be from the Local Void, an empty area of space bordering
the Milky Way galaxy.
-
- The particles are
so high energy, they shouldn’t be affected by galactic and extra-galactic
magnetic fields. You should be able to point to where they come from in the
sky. But in the case of the Oh-My-God
particle and this new particle, you trace its trajectory to its source and
there’s nothing high energy enough to have produced it.
-
- A single beam of
light has a straight line from space to Earth. A less energetic ray is coming into Earth in a swirly curly pathway.
-
- These events seem
like they’re coming from completely different places in the sky. It’s not like
there’s one mysterious source. It could
be defects in the structure of spacetime, colliding cosmic strings.
-
- Cosmic rays are
echoes of violent celestial events that have stripped matter to its - subatomic
structures and hurled it through universe at nearly the speed of light.
Essentially cosmic rays are charged particles with a wide range of energies
consisting of positive protons, negative electrons, or entire atomic nuclei
that travel through space and rain down onto Earth nearly constantly.
-
- Cosmic rays hit
Earth’s upper atmosphere and blast apart the nucleus of oxygen and nitrogen
gas, generating many secondary particles. These travel a short distance in the
atmosphere and repeat the process, building a shower of billions of secondary
particles that scatter to the surface.
-
- The footprint of
this secondary shower is massive and requires that detectors cover an area as
large as the Telescope Array. The surface detectors utilize a suite of
instrumentation that gives researchers information about each cosmic ray; the
timing of the signal shows its trajectory and the amount of charged particles
hitting each detector reveals the primary particle’s energy.
-
- Because particles
have a charge, their flight path resembles a ball in a pinball machine as they
zigzag against the electromagnetic fields through the cosmic microwave
background. It’s nearly impossible to trace the trajectory of most cosmic rays,
which lie on the low- to middle-end of the energy spectrum.
-
- Even high-energy
cosmic rays are distorted by the microwave background. Particles with Oh-My-God
and Amaterasu energy blast through intergalactic space relatively unbent. Only
the most powerful of celestial events can produce them.
-
- Things that people
think of as energetic, like supernova, are nowhere near energetic enough for
this. You need huge amounts of energy, really high magnetic fields to confine
the particle while it gets accelerated.
-
- Ultra-high-energy
cosmic rays must exceed 5 x 10^19 electronvolts. This means that a single
subatomic particle carries the same kinetic energy as a major league pitcher’s
fast ball and has tens of millions of times more energy than any human-made
particle accelerator can achieve.
-
- Astrophysicists
calculated this theoretical limit as the maximum energy a proton can hold
traveling over long distances before the effect of interactions of the
microwave background radiation take their energy.
-
- Known source
candidates, such as active galactic nuclei or black holes with accretion disks
emitting particle jets, tend to be more than 160 million light years away from
Earth. The new particle’s 2.4 x 10^20 eV and the Oh-My-God particle’s 3.2 x
10^20 eV easily surpass the cutoff.
-
- Researchers also
analyze cosmic ray composition for clues of its origins. A heavier particle,
like iron nuclei, are heavier, have more charge and are more susceptible to
bending in a magnetic field than a lighter particle made of protons from a
hydrogen atom.
-
- The new particle
is likely a proton. Particle physics dictates that a cosmic ray with energy
beyond the GZK cutoff is too powerful for the microwave background to distort
its path, but back tracing its trajectory points towards empty space.
-
- Maybe magnetic
fields are stronger than we thought, but that disagrees with other observations
that show they’re not strong enough to produce significant curvature at these
10^20 electron volt energies.
-
- The Telescope
Array is uniquely positioned to detect ultra-high-energy cosmic rays. It sits
at about 4,000 foot elevation that allows secondary particles maximum
development, but before they start to decay. Its location in Utah’s West Desert
provides ideal atmospheric conditions in two ways: the dry air is crucial
because humidity will absorb the ultraviolet light necessary for detection; and
the region’s dark skies are essential, as light pollution will create too much
noise and obscure the cosmic rays.
-
- Astrophysicists
are still baffled by the mysterious phenomena. The Telescope Array is in the
middle of an expansion that that they hope will help crack the case. Once
completed, 500 new scintillator detectors will expand the Telescope Array will
sample cosmic ray-induced particle showers across 1,100 miles^2 , an area
nearly the size of Rhode Island.
-
- The larger
footprint will hopefully capture more events that will shed light on what’s
going on.
-
-
November 30, 2023
COSMIC RAYS - the
highest energy 4249
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