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Up in the sky — faster than a speeding LHC proton

John Healy

This Space.com article “Hotspot for Cosmic Rays: Touring the Telescope Array Project in Utah” published on May 27, 2017, reminded me that while CERN’s LHC is the current champ of colliders on Earth, other particles which have been raining down on us for billions of years are colliding with Earth’s atmosphere at even higher energies — the mysterious so-called cosmic rays.

The term ray is a historical accident, as cosmic rays were at first, and wrongly, thought to be mostly electromagnetic radiation. In common scientific usage, high-energy particles with intrinsic mass are known as “cosmic” rays, while photons, which are quanta of electromagnetic radiation (and so have no intrinsic mass) are known by their common names, such as gamma rays or X-rays, depending on their photon energy.

Cosmic ray research is an active field of study using both ground and space based observatories. The Telescope Array Project is profiled in the Space.com article.

By studying the particles that cascade to Earth, scientists can learn about the energy of the original cosmic rays. Traveling through space, the cosmic rays are rapidly accelerated to energy levels millions of times higher than particles inside the Large Hadron Collider, the most powerful particle accelerator ever built. [The Telescope Array Project: A Photo Tour]

A Forbes.com article “Cosmic Rays May Reveal New Physics Just Out Of LHC’s Reach” published on November 29, 2016, also points out that cosmic rays are speedier than LHC protons.

The Large Hadron Collider (LHC) – presently the world’s most powerful particle accelerator – reaches a maximum collision energy of 14 TeV. Two protons, moving at 299,792,455 m/s apiece, or a tantalizing 99.9999991% the speed of light, collide, leaving a maximum of 14 TeV of energy available for the creation of new particles. But the cosmic rays that collide with atoms in the upper atmosphere have been measured with speeds in great excess of these, resulting in collision energies about ten times as high as anything the LHC can muster.

And this PBS.org article “The Astronomical Particle Colliders That Put Our Own to Shame” published on July 21, 2014,  makes the same point; and, furthermore, addresses the fear than some raised about the operation of the LHC.

When the Large Hadron Collider (LHC) began operations, a small but noisy group of people tried to stop it out of fear. Their reasoning: The energies produced as protons slammed into each other at close to the speed of light would be sufficiently high to create miniature black holes or other exotic, destructive things. The fruits of human curiosity would be the literal end of the world.

Those fears were unwarranted for a simple reason: Earth is bombarded by much higher-energy particles all the time, and we haven’t been eaten by a planet-munching black hole yet. In fact, the universe has many naturally-occurring particle accelerators that are far more powerful than the LHC, exceeding even anything we could build in the foreseeable future. Anything exotic we can create in our labs, the cosmos has beaten us to it.

“The energy for particle creation … in the upper atmosphere is more than a factor of twenty greater than at the LHC,” said Glennys Farrar, professor of physics at New York University. Most impressive of all are “ultra-high-energy” cosmic rays, which reach energies 100 million times greater than the fastest protons produced in the LHC.

Can cosmic rays be used to detect Higgs bosons like at the LHC? Unlikely, since a Higgs boson lasts around a zepto second and detectors need to be close to collisions and require massive equipment and processing to separate out exotic particles from bursts of ordinary ones.

Some possible sources of ultra-high-energy cosmic rays are neutron stars.

 

2 thoughts on “Up in the sky — faster than a speeding LHC proton”

  1. What’s really happening during an LHC collision?

    Protons are made up of three quarks and an indefinable number of gluons. …

    “The inside of a proton would look like the atmosphere around you,” says Richard Ruiz, a theorist at Durham University. “It’s a mixture of empty space and microscopic particles that, for all intents and purposes, have no physical volume.

    “But if you put those particles inside a balloon, you’ll see the balloon expand. Even though the internal particles are microscopic, they interact with each other and exert a force on their surroundings, inevitably producing something which does have an observable volume.”

    In particle physics, the term “collide” can mean that two protons glide through each other, and their fundamental components pass so close together that they can talk to each other. If their voices are loud enough and resonate in just the right way, they can pluck deep hidden fields that will sing their own tune in response—by producing new particles.

  2. Here’s a cosmic detective story – identifying sources of extremely accelerated protons (and atomic nuclei and electrons). Magnetic field dynamics and shockwave modeling link telltales near the masked origins. Gamma ray glow.

    • Phys.org > “NASA’s Fermi telescope confirms star wreck as source of extreme cosmic particles” by Francis Reddy, NASA (August 10, 2022) – A study published August 10 in the journal Physical Review Letters used 12 years of data from NASA’s Fermi Gamma-ray Space Telescope to confirm that a supernova remnant is a source of (so-called) cosmic rays. (Article includes YouTube video.)

    “Theorists think the highest-energy cosmic ray protons in the Milky Way reach a million billion electron volts, or PeV energies,” said Ke Fang, an assistant professor of physics at the University of Wisconsin, Madison. “The precise nature of their sources, which we call PeVatrons, has been difficult to pin down.”

    Trapped by chaotic magnetic fields, the particles repeatedly cross the supernova’s shock wave, gaining speed and energy with each passage. Eventually, the remnant can no longer hold them, and they zip off into interstellar space [1].

    Boosted to some 10 times the energy mustered by the world’s most powerful particle accelerator, the Large Hadron Collider, PeV protons are on the cusp of escaping our galaxy altogether.

    Notes

    [1] As visualized in this video:

    • YouTube > NASA Goddard > “Fermi Proves Supernova Remnants Produce Cosmic Rays” (Feb 14, 2013)

    A new study using observations from NASA’s Fermi Gamma-ray Space Telescope reveals the first clear-cut evidence that the expanding debris of exploded stars produces some of the fastest-moving matter in the universe. This discovery is a major step toward meeting one of Fermi’s primary mission goals.

    Cosmic rays are subatomic particles that move through space at nearly the speed of light. About 90 percent of them are protons, with the remainder consisting of electrons and atomic nuclei. In their journey across the galaxy, the electrically charged particles become deflected by magnetic fields. This scrambles their paths and makes it impossible to trace their origins directly.

    Through a variety of mechanisms, these speedy particles can lead to the emission of gamma rays, the most powerful form of light and a signal that travels to us directly from its sources.

    Two supernova remnants, known as IC 443 and W44, are expanding into cold, dense clouds of interstellar gas. This material emits gamma rays when struck by high-speed particles escaping the remnants.

    Scientists have been unable to ascertain which particle is responsible for this emission because cosmic-ray protons and electrons give rise to gamma rays with similar energies. Now, after analyzing four years of data, Fermi scientists see a gamma-ray feature from both remnants that, like a fingerprint, proves the culprits are protons.

    When cosmic-ray protons smash into normal protons, they produce a short-lived particle called a neutral pion. The pion quickly decays into a pair of gamma rays. This emission falls within a specific band of energies associated with the rest mass of the neutral pion, and it declines steeply toward lower energies.

    Detecting this low-end cutoff is clear proof that the gamma rays arise from decaying pions formed by protons accelerated within the supernova remnants.

    Related posts

    • Cosmic retrospective — gamma ray bursts

    Fermi Proves Supernova Remnants Produce Cosmic Rays

    This multiwavelength composite shows the supernova remnant IC 443, also known as the Jellyfish Nebula.

    • Fermi GeV gamma-ray emission is shown in magenta
    • Optical wavelengths as yellow
    • Infrared data from NASA’s Wide-field Infrared Survey Explorer (WISE) mission is shown as blue (3.4 microns), cyan (4.6 microns), green (12 microns) and red (22 microns)

    Cyan loops indicate where the remnant is interacting with a dense cloud of interstellar gas.

    Credit: NASA/DOE/Fermi LAT Collaboration, NOAO/AURA/NSF, JPL-Caltech/UCLA [February 14, 2013]

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