Galactic Cosmic Rays
Galactic cosmic rays (GCRs) come from outside the solar system but generally from within our Milky Way galaxy. GCRs are atomic nuclei from which all of the surrounding electrons have been stripped away during their high-speed passage through the galaxy. They have probably been accelerated within the last few million years, and have traveled many times across the galaxy, trapped by the galactic magnetic field. GCRs have been accelerated to nearly the speed of light, probably by supernova remnants. As they travel through the very thin gas of interstellar space, some of the GCRs interact and emit gamma rays, which is how we know that they pass through the Milky Way and other galaxies.
The elemental makeup of GCRs has been studied in detail , and is very similar to the composition of the Earth and solar system. but studies of the composition of the isotopes in GCRs may indicate the that the seed population for GCRs is neither the interstellar gas nor the shards of giant stars that went supernova. This is an area of current study.
Included in the cosmic rays are a number of radioactive nuclei whose numbers decrease over time. As in the carbon-14 dating technique, measurements of these nuclei can be used to determine how long it has been since cosmic ray material was synthesized in the galactic magnetic field before leaking out into the vast void between the galaxies. These nuclei are called "cosmic ray clocks". Read about an experiment helping us to study GCRs: TIGER, the Trans-Iron Galactic Element Recorder Galactic Cosmic Rays in the News:
August 28, 2008: Fermi's first
light -- APOD
August 26, 2008: NASA renames observatory for Fermi, reveals entire gamma-ray sky -- NASA August 13, 2008: Physicists await dark matter confirmation -- Nature July 5, 2008: First underwater neutrino telescope has been constructed -- Science Daily March 20, 2008: Rare cosmic rays are from far away -- Eurekalert March 18, 2008: Fly's eye detector spies cosmic-ray cut-off -- Nature March 4, 2008: GLAST spacecraft arrives in Florida to prepare for launch -- NASA KSC February 15, 2008: NASA sponsors studies of next generation astronomy missions -- NASA February 8, 2008: NASA calls for suggestions to rename future telescope mission -- NASA GSFC January 24, 2008: Do cosmic rays cause lightning? -- Scientific American January 4, 2008: Scientific balloons achieve Antarctic flight record -- NSF January 2, 2008: White dwarf pulses like a pulsar -- NASA GSFC January 2, 2008: Hot on the trail of cosmic rays -- Space.com December 22, 2007: The best of 2007 -- Physics World December 21, 2007: Cosmic powerhouses -- Astronomy.com December 20, 2007: Suzaku explains cosmic powerhouses -- NASA GSFC December 13, 2007: Ten top physics stories for 2007 -- AIP December 4, 2007: Radiation flashes crack cosmic mystery -- Astronomy.com November 30, 2007: NASA's GLAST satellite arrives at Naval Research Lab for testing -- Reuters November 29, 2007: Violent black holes linked to high-energy cosmic rays -- The Hindu November 20, 2007: Pierre Auger Observatory pinpoints source of mysterious highest-energy cosmic rays -- CERN Courier November 20, 2007: Egyptian pyramids -- AIP November 12, 2007: The highest-energy cosmic rays -- AIP November 12, 2007: Cosmic rays from galactic centers -- APOD November 10, 2007: Ray tracing: Energetic cosmic rays linked to giant black holes -- Science News November 9, 2007: Energetic cosmic rays may start from black holes -- NY Times November 8, 2007: Monster black holes power highest-energy cosmic rays -- New Scientist November 8, 2007: Fastball-strength cosmic rays traced to black holes -- Scientific American November 8, 2007: Cosmic-ray mystery solved at last -- Physics World October 31, 2007: The origin of energetic 3He in the inner heliosphere -- ACE News October 11, 2007: Origin of cosmic rays illuminated -- Science Daily October 9, 2007: NASA: Major step toward knowing origin of cosmic rays -- NASA GSFC September 18, 2007: Large Hadron Collider project to study the origins of matter -- Science Daily September 13, 2007: Cassini flies by Saturn's walnut-shaped moon Iapetus -- Science Daily August 31, 2007: Celebrating 10 years of ACE in space -- ACE News August 17, 2007: In search of interstellar dragon fire -- NASA GSFC May 23, 2007: UD scientists build an 'ice top' at the bottom of the world -- EurekAlert! March 21, 2007: Making cosmic gamma rays -- Astronomy.com February 28, 2007: NASA MESSENGER mission news: Priming instruments to map Mercury's crust -- SpaceRef.com February 21, 2007: Space radiation hazards and the vision for space exploration: A report on the October 2005 Wintergreen conference -- AGU Space Weather February 7, 2007: South pole flyby -- Science@NASA January 30, 2007: Superbubble origin of galactic cosmic rays supported by supernova-produced isotopes -- ACE News Click on images above to
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