Researchers have found what they believe is the source of high-power cosmic rays, which are the most energetic particles in the universe.
Cosmic rays are super-charged protons that are expelled from our own sun and other stars at low-energy levels. Medium-level cosmic rays are known to originate from exploding stars. There are still some theories as to where high-energy cosmic rays originate, but recent findings show it is likely the environment that surrounds black holes.
A study compiled by researchers at the U and 90 other institutions from 17 nations found that cosmic rays are likely created in quasars or the areas surrounding black holes located in distant galaxies.
The volatile environment in these quasars, usually found at the center of galaxies and the violent environment that surrounds them, has the potential to create these high-powered cosmic rays.
“We’re not sure how these galaxies create these particles and how they reach such high levels of energy, but something in these active galactic nuclei is causing these high-powered cosmic rays,” said David Thomas, a graduate student in physics. “Now we have an idea of where these rays are coming from, and I’d expect there will be more research into the specific causes for these high-powered cosmic rays.”
Cosmic rays are measured in electron volts. Of the rays observed in the study, 77 exceeded 40 billion electron volts. The 27 most energetic rays, also called high-power cosmic rays, were recorded at 57 billion billion electron volts. Seven of those rays were found to be correlated with the direction of nearby areas with black holes, the study said.
According to U professor Miguel Mostafa’s research, a single subatomic particle traveling at the rate of a high-powered cosmic ray would feel like a fast-pitched baseball if it hit someone in the head.
High-powered cosmic rays can only be tracked as they enter into the earth’s atmosphere, causing a shower of charged molecules. Many lower-powered cosmic rays hit the earth every day, but they have much less energy and are more common than the high-power rays.
Patrick Younk, a research assistant in the physics department, compared the rays’ entry into the earth’s atmosphere to a subatomic car accident. When the charged proton in the cosmic ray enters the atmosphere, it collides with the nuclei of air molecules. This initial collision causes cascading wrecks among air molecules, creating a charged molecular shower.
At the Auger Observatory in western Argentina, researchers record these cosmic showers in 16,000 water tanks that span 3,000 square kilometers — a land mass roughly the size of Rhode Island. The water tanks house phototubes that record the number of charged molecular fallout from the cosmic ray’s entry path and the strength by measuring the light emitted.
“The shower front travels on a plane perpendicular to the ray’s direction of arrival,” Thomas said. “From the timing of the fallout into the tanks you can calculate the direction that the ray came from.”
According to Mostafa, the galaxies emitting these high-power cosmic rays must be relatively close to the Milky Way Galaxy, around 326 million light years away.
U of U News CenterUniversity of Utah physicist Miguel Mostafa stands in Argentina by one of the Pierre Auger Observatory’s 1,600 water tanks that detect “air showers” of particles generated when incoming cosmic rays hit Earth’s atmosphere.