Galactic Cosmic Rays

Galactic Cosmic Rays in the News

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.

The image on the right is the EGRET gamma ray all-sky survey, courtesy of Dr. Carl Fichtel and the EGRET Instrument Science Team. Some GCRs interact with the interstellar medium and produce gamma rays. More about the interstellar medium...

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

Back to cosmic rays

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

Galactic cosmic ray news from 2006 and earlier