Cosmic Ray Mystery Solved
Universe's Most Energetic Particles Point Back to Super-Massive Black Holes
Nov. 8, 2007 - The most energetic particles in the universe - ultrahigh-energy cosmic rays - likely come from supermassive black holes in the hearts of nearby active galaxies, says a study by scientists from nearly 90 research institutions worldwide, including the University of Utah.
"We discovered the sources of the highest energy particles in the universe," says Miguel Mostafá, an assistant professor of physics at the University of Utah and one of 370 scientists and engineers belonging to a 17-nation collaboration that operates the $54 million Pierre Auger Observatory in Argentina.
"The sources are the center regions of very active galaxies which host violent black holes" and are known as "active galactic nuclei," he adds. "Now that we found the sources, we are one step closer to knowing what physical process can accelerate particles to these ultrahigh energies."
The study by the Pierre Auger Collaboration is being published in the Friday, Nov. 9 issue of the journal Science. Members of the collaboration at the University of Utah are Mostafá physicist and Dean of Science Pierre Sokolsky; postdoctoral research associate Patrick Younk; and physics graduate student David Thomas. Two undergraduate students - Joshua Schmeiser and Felix Lau - also work on the project.
Surface detector in the Argentinean Pampas (plus Prof. Mostafá plus local inhabitant...)
Black holes are collapsed stars with gravity so strong that nothing - not even light - can escape once it has fallen past the black hole's "event horizon." Scientists believe most galaxies, including ours, host supermassive black holes, which contain the mass of up to a few billion stars like our sun.
When matter is sucked into supermassive black holes, the process also spews out various particles and electromagnetic radiation, from gamma and X-rays to ultraviolet, visible and infrared light, and radio waves. A galaxy with a compact center that is extremely, persistently bright in all or some wavelengths is known as an active galactic nucleus (AGN). Only a fraction of galaxies with supermassive black holes are AGNs.
For more information follow the links at the bottom of the page.
The UoU group contribution
Mostafá's group at the University of Utah played a key role in designing, building and operating two lasers and four lidar (light detection and ranging) devices to monitor dust, clouds, water vapor and other atmospheric conditions above the Auger Observatory.
The devices ensure the accuracy of the fluorescence telescopes by helping scientists determine how much light is generated by a cosmic ray air shower, and how much that light is enhanced when it scatters off dust and vapor in the atmosphere.
Mostafá's group also developed the "geometrical reconstruction technique" to analyze "hybrid" data from Auger's tank-like particle detectors and florescence-detecting telescopes. The computer software uses that data to provide more precise information on the direction in space from which an incoming ultrahigh-energy cosmic ray originated.
Mostafá's geometrical reconstruction method also will help physicists learn more about the specific process responsible for hurling ultrahigh-energy cosmic rays across space. While the black holes are thought to accelerate cosmic rays, another kind of theory holds that the highest-energy cosmic rays are photons - light particles - produced by the decay of superheavy particles left over from the birth of the universe. Mostafá's method shows there are few if any photons with energy levels consistent with such theories.
While the Southern Pierre Auger Observtory continues taking data at the largest energies ever detected, Mostafá's group is responsible for designing the fluorescence detectors at the planned Northern Observatory to be located in southeast Colorado. Stay tuned!
For more information on Auger and this result follow these links below.
| More Info | URL |
|---|---|
| Information and photos on the Auger Observatory | http://www.auger.org/media |
| Pierre Auger Collaboration Official Release | http://www.auger.org/news/PRagn/AGN_correlation.html |