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Physicists Identify Cosmic Ray "Hot Spots," Raising Questions About Understanding of Galactic Magnetic Fields Near Our Solar System

November 24, 2008
N-181, 2008-09

Physicists have observed for the first time two distinct hot spots that appear to be showering Earth with an excess of cosmic rays. The discovery calls into question nearly a century of understanding about galactic magnetic fields near our solar system because it raises the possibility that an unknown source or magnetic effect is responsible for these observations.

Their findings, published in the latest issue of the Physical Review Letters, were obtained using the Milagro Gamma Ray Observatory, a detector located at Los Alamos National Lab in New Mexico that allows monitoring of the northern sky on a 24-hour, 7-day-per-week basis.

The research team, comprised of researchers from more than a dozen institutions, including New York University, used the Milagro cosmic-ray observatory to peer into the sky above the northern hemisphere for nearly seven years starting in July 2000. The observatory is unique in that it monitors the entire sky above the northern hemisphere. Because of its design and field of view, Milagro was able to record over 200 billion cosmic-ray collisions with the Earth’s atmosphere.

Cosmic rays are high-energy particles that move through our galaxy from distant sources. Cosmic rays’ origins are unknown, but scientists have theorized they might originate from supernovae-massive stars that explode-from quasars, or from less-understood or yet-to-be-discovered sources within the universe. However, because cosmic rays are charged particles, magnetic fields from the Milky Way and our solar system change the flight paths of the particles so much that researchers had not been able to pinpoint their exact origin. Consequently, traditional wisdom has held that no localized area of excess of cosmic rays should appear in the sky.

But because Milagro recorded so many cosmic-ray events, researchers for the first time were able to see statistical peaks in the number of cosmic-ray events originating from specific regions of the sky near the constellation Orion. The region with the highest hot spot of cosmic rays is above and to the right visually of Orion, near the constellation Taurus. The other hot spot is a comma-shaped region near the constellation Gemini. Overall, the discovery of these “hot spots” raises the possibility that an unknown source or magnetic effect near our solar system is responsible for these observations.

The NYU collaborators on this work included: Roman and Lazar Fleysher, post-doctoral fellows at the Department of Radiology in the NYU School of Medicine who conducted the work as doctoral students in NYU’s Department of Physics; Brian Kolterman, who earned his doctorate in physics at NYU; and Allen Mincer and Peter Nemethy, professors in NYU’s Department of Physics.

Funding for the research came from the U.S. Department of Energy’s Office of High-Energy Physics and Office of Nuclear Physics; Los Alamos National Laboratory’s Laboratory-Directed Research and Development fund and the Laboratory’s Institute for Geophysics and Planetary Physics; and the National Science Foundation.

This Press Release is in the following Topics:
Graduate School of Arts and Science, Research

Type: Press Release

The localized regions of excess cosmic rays (in red) observed by Milagro superimposed on a star map in this region. The Orion constellation is connected  by white lines in the lower part of the image.

The localized regions of excess cosmic rays (in red) observed by Milagro superimposed on a star map in this region. The Orion constellation is connected by white lines in the lower part of the image.

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