The "Oh My God Particle" is one of the most amusing names scientists have encountered
in the physics field. One of the first things that may come to your
mind when you hear this name is the Higgs Boson, which was discovered in 2012. This
isn't too surprising as it was dubbed the "God Particle" by the media.
But these two particles are vastly different. The Oh My God Particle has such a strange
and godly nature that scientists couldn’t resist naming it ‘Oh My God’.
So, what is the Oh My God Particle? It is an ultra-high-energy cosmic ray detected on
15 October 1991 by the Fly's Eye camera in Dugway Proving Ground, Utah, U.S. It was the
highest-energy cosmic ray that had ever been observed at the time.
Although higher energy cosmic rays have since been detected, the energy of this particle
was unexpected, calling into question the origin and transmission of cosmic rays at
that time. Since its discovery, scientists have been
baffled by the Oh My God Particle, a form of cosmic ray mainly protons (hydrogen nuclei).
A single atomic nucleus moving at 99.99% the speed of light smashed through Earth's atmosphere
and flashed across the Utah sky. The nucleus shattered into a shower of subatomic particles
and lights in a matter of seconds. The light was detected by the Fly's Eye Observatory,
a collection of oversized tin cans used by the University of Utah as part of an early
experiment to detect high-energy cosmic rays in the universe.
According to scientists examining the data from Fly's Eye, the cosmic ray responsible
for this specific flash must have had a kinetic energy of 3 x 1020 electron volts (eV). That's
48 joules, a unit of energy that we identify with macroscopic objects rather than subatomic
ones. That single atomic nucleus has the same amount
of kinetic energy as a large stone thrown at you at 50 miles per hour. The particle
was dubbed Oh My God. Scientists had never seen anything like it before. In fact, such
high-energy cosmic rays were thought to be non-existent.
Most cosmic ray particles are mainly single protons, the nuclei of hydrogen atoms, and
a small number of helium nuclei. However, roughly 1% of cosmic rays have heavier nuclei,
as heavy as iron. Gamma rays and even anti-matter particles
come in at energies ranging from a few billion electron volts at the low end to a mind-boggling
1020 electron volts or greater, such as the Oh-My-God particle.
The higher the energy, the rarer the particles are.
The universe flings one particle every second per square meter of the Earth's surface at
the lowest energies. They are scarce at energies close to those of the Oh My God Particle.
Since the first one, just a few have been discovered, giving a rare estimate of one
per square kilometer every couple of centuries. Most cosmic ray particles now have low energy,
up to 1010 electron volts, and are generated locally by solar flares.
Another more energetic class, with energies up to 1015 electron volts, is thought to come
from somewhere else in the galaxy. It's difficult to determine their specific
source as the magnetic fields of the galaxy and the solar system affect their trajectories.
So they end up with a uniform distribution in the sky as if they come from everywhere.
However, these galactic cosmic rays are most likely the result of supernovae, maybe in
a delayed-release process as particles bounce back and forth in the supernova remnant's
magnetic field before being launched out into the wider galaxy.
Then there are extragalactic cosmic rays of the Oh-My-God type, with energies exceeding
1015 electron volts and even reaching 1020 electron volts on rare occasions.
They are formally known as ultra-high-energy cosmic rays.
These particles travel at near-light speeds and must have had a lot of energy to achieve such
speeds. However, the origin of extragalactic cosmic
rays has long been shrouded in an exaggerated atmosphere of mystery, as reflected by the
Oh-My-God title. Cosmic ray astronomy is becoming a more potent
tool for understanding our fascinating world as we learn more about its origins. However,
these particles are still useful today. The highest-energy cosmic rays, such as the
Oh-My-God particle, produce significantly more energetic collisions than our largest
particle accelerator, the Large Hadron Collider. More research on cosmic rays could reveal
the mysteries of both the largest and tiniest scales of space-time.