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Most Powerful Cosmic Rays Come From Galaxies Far, Far Away (space.com)
A new study finds the highest-energy cosmic rays to bombard Earth come from galaxies far, far away. Space.com reports: The sun emits relatively low-energy cosmic rays. However, for more than 50 years, scientists have also detected ultra-high-energy cosmic rays, ones far beyond the capability of any particle accelerator on Earth to generate. One way to discover the origins of ultra-high-energy cosmic rays is to study their directions of travel. However, ultra-high-energy cosmic rays only rarely strike Earth's atmosphere, with one hitting any given area about the size of a soccer field about once per century, the researchers said. In order to detect ultra-high-energy cosmic rays, scientists look for the spray of electrons, photons and other particles that result when ultra-high-energy cosmic rays hit the top of Earth's atmosphere. Each of these showers contains more than 10 billion particles, which fly downward in a disk shaped like a giant plate miles wide, according to the statement. Scientists examined the sprays from ultra-high-energy cosmic rays using the largest cosmic-ray observatory yet: the Pierre Auger Observatory built in the western plains of Argentina in 2001. It consists of an array of 1,600 particle detectors deployed in a hexagonal grid over 1,160 square miles (3,000 square kilometers), an area comparable in size to Rhode Island. A connected set of telescopes is also used to see the dim fluorescent light the particles in the sprays emit at night.
The researchers analyzed data collected between 2004 and 2016. During these 12 years, the scientists detected more than 30,000 ultra-high-energy cosmic rays. If ultra-high-energy cosmic rays came from the Milky Way, one might perhaps expect them to come from all across the sky, or perhaps mostly from the direction of the supermassive black hole at the galaxy's center. However, the researchers saw that ultra-high-energy cosmic rays mostly came from a broad area of sky about 90 degrees away from the direction of the Milky Way's core.
The researchers analyzed data collected between 2004 and 2016. During these 12 years, the scientists detected more than 30,000 ultra-high-energy cosmic rays. If ultra-high-energy cosmic rays came from the Milky Way, one might perhaps expect them to come from all across the sky, or perhaps mostly from the direction of the supermassive black hole at the galaxy's center. However, the researchers saw that ultra-high-energy cosmic rays mostly came from a broad area of sky about 90 degrees away from the direction of the Milky Way's core.
Perhaps there is another way of looking at the data.
When dealing with astronomical observations of this type, we accept that the observations we are making could be millions or even billions of years old, based on the distance from which the phenomena originate. OK, so: old data.
We are also told by physicists that our universe started with a "big bang", a state and point in time at which the state of our universe was so energised that the sub-atomic particles we take for granted today [never mind atoms and molecules] did not exist - because the universe had not cooled sufficiently.
So if you extrapolate this facts, don't they suggest that it stands to reason that, the further away in distance [and thus the further back in time] that we look, the higher the energies we would expect to observe. Everything else is [just / subject to] entropy.
I'm not sure where Occam's Razor would swing across this story, but suspect the explanation - whatever it is - will be a simple one.
Way, way back in the 1980s as an Honors CS student I wrote some code on an old DG Nova to analyze cosmic ray bursts for the Physics Dept (Uni Adelaide). They had several detectors, hooked into a CAMAC crate, and could measure the time difference between the receptors, and thus the direction of the burst, or at least where the cosmic ray hit the atmosphere, and by also looking at distributions work out roughly which direction the original ray came from.
Some of them are charged particles and so do not travel in straight lines, which complicates it. I just did the programming, not much to do with the physics, but I would have thought this would be old news.