- 4296 - PARTICLE PHYSICS - new things learned in 2023? Astronomers were stunned to discover what they later named the Oh-My-God particle, a cosmic ray streaking into Earth's atmosphere with a blistering 320 exa-electron-volts (EeV) of energy. On a human scale, that's not a big number, roughly the energy of a dropped basketball hitting the ground. But for subatomic particles, it's gigantic, far outpacing even our most powerful collider experiments.
-------------- 4296 - PARTICLE PHYSICS - new things learned in 2023?
------------ The OMG
particle got a partner: a 240 EeV particle dubbed “Amaterasu”, named after the
goddess of the sun in Japanese mythology. Discovered with the Telescope Array
Project in Utah, the new particle joins a rarefied list of ultra-relativistic
high-energy cosmic rays. These rare particles come from the most energetic
events in the universe but are ultimately mysterious. Amaterasu appeared to come from the direction
of the Local Void, a big batch of nothing in our cosmological neighborhood.
-
------------
Astronomers around the world are on the hunt for neutrinos. These "ghost particles" are
produced in all sorts of nuclear and high-energy reactions, but they hardly
ever interact with normal matter. So, to catch neutrinos, astronomers have
turned to massive observatories, like the IceCube Neutrino Observatory, which
turns an entire cubic kilometer of the Antarctic ice sheet into a neutrino
detector.
-
- Using that
sensitive instrument, this year astronomers announced that our own Milky Way
galaxy is producing neutrinos. While we've long known that other, more distant
galaxies produce copious amounts of neutrinos, this was the first direct
evidence that our galaxy does, too, thus opening up a brand-new pathway in
neutrino science.
-
--------- Pulsars are
already known to be amazing objects. They're formed from neutron stars, which
are the leftover cores of dead stars. They can compress several times the mass
of the sun into a volume no bigger than a city. The fastest ones spin faster
than your kitchen blender. Sometimes, they shoot out beams of radiation, and
when those beams happen to wash over Earth, we call them pulsars.
-
- This year,
astronomers added another superlative: the most energetic gamma-ray photons
ever detected from a pulsar. Using the High Energy Stereoscopic System
observatory in Namibia, the astronomers saw the photons coming from a pulsar
located about 1,000 light-years away in the direction of the constellation
Vela. A single photon at these energies is over 2 million times more powerful
than the photons associated with a typical solar flare.
-
------- Pulsars
aren't the only astronomical object capable of blasting them out. In fact, some
explosions are so intense that they're known appropriately as gamma-ray bursts.
In 2022, astronomers observed the brightest gamma-ray burst ever seen, which
they dubbed the "BOAT," for
"brightest of all time."
-
- In 2023, a
different team of astronomers determined that the BOAT, which originated in a
galaxy behind the Milky Way, was powerful enough to disturb the upper layer of
Earth's atmosphere. The intense radiation affected the ionosphere, which sits
between an altitude of 31 and 217 miles (between 50 and 350 kilometers). The
effect wasn't very big, but the fact that there was any effect at all is
surprising.
-
------------
Antimatter is just like normal matter, except it has an opposite charge.
For example, a positron has the same mass and spin as an electron, but has a
positive charge rather than a negative one. First discovered in the early 20th
century, antimatter is a major cornerstone of theoretical physics. But besides
the charge, just how identical are antimatter and normal matter? This year,
physicists determined that it all acts the same, especially in response to
gravity.
-
- General relativity
says that antimatter and matter should behave exactly the same, but no
conclusive tests had been performed until this year. It's not exactly a
surprising result, but it's good to check these kinds of things off the list.
After all, nature has plenty of surprises for us, and you never know where you
might find them.
-
-------------
Neutrinos come in all sorts of energies and from a variety of exotic
sources. In 2023, astronomers learned of one more: giant black holes. The black
holes themselves don't create neutrinos, after all, nothing can escape their
gravitational clutches, but the gas swirling into their gaping maws certainly
can. There, the plasma whips up to a healthy fraction of the speed of light and
heats up to trillions of degrees. That's more than enough energy to produce all
sorts of crazy particles, including neutrinos, which astronomers found
constantly washing over Earth.
-
--------------------
Most of the matter in the universe is a mysterious form of matter known
as dark matter, which we can detect only indirectly via its gravitational
influence on galaxies and the larger universe. There is no altered theory of
gravity that can explain the results, so our current best guess is that dark
matter is some sort of unknown particle.
-
- Scientists have
been searching for signs of this particle with detectors scattered around the
world, and this year, the Super Cryogenic Dark Matter Search collaboration
announced … that they haven't found it. This isn't a bad thing; the team did
provide tighter constraints on what dark matter isn't, which helps narrow down
future searches, but the hunt continues.
-
----------------------
Dark matter is so mysterious that there may be whole new areas of
physics that are currently invisible to us. For example, there could be a new,
fifth force of nature that operates only among different kinds of dark matter
particles. This force would need its own carrier, which has been dubbed the
"dark photon," because that sounds really epic.
-
-------------------
The world of dark matter can get even weirder. Not satisfied with just
one kind of particle? A new force of nature not enough? Well, how about an
entire dark periodic table, with different "species" of dark matter
particles interacting in their own elaborate, invisible dance? This leads to a
deeply hypothetical idea known as dark atoms, where dark matter particles
bundle up together in the hearts of galaxies. According to new research this
year, these dark atoms can go on to influence the rate of star production in
their host galaxies, a potentially observable effect.
-
----------------------
The early universe really knew how to throw a party. Within the first
second after the Big Bang, the forces of nature split off from their united
state, creating the cosmos that we know and love today. These
"splittings" were violent and energetic, and they didn't happen all
at once across the universe.
-
- As each force
broke off, bubbles of the new reality formed, expanded and collided with each
other. This year, physicists discovered that the colliding bubbles would make
for excellent particle accelerators. Dubbed "bubbletrons," they just
might be responsible for the creation of most of the particles we're familiar
with.
-
---------------------
The sun is our closest star, so it's also our nearest laboratory for
stellar physics. This year, using the High-Altitude Water Cherenkov Observatory
in Mexico, astronomers discovered that our star is far more energetic than we
previously thought. The sun is perfectly capable of generating excess
gamma-rays, the highest-energy form of radiation. While that radiation doesn't
harm us directly, it does show that there's still a lot to learn about the sun.
-
-
December 18, 2023 PARTICLE PHYSICS
- new things learned in 2023? 4296
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