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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.
![Image of the sky in gamma rays](gamma.gif)
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
January 7, 2009: Danger
ahead as the Sun goes quiet -- New Scientist
January 6, 2009: Cassiopeia
A comes alive across time and space -- NASA's Chandra mission
December 31, 2008: Top ten physics stories of
the year -- includes the Large Hadron Collider, quarks, and GCRs -- American
Institute of Physics (AIP)
December 17, 2008: Cosmic
rays do not explain global warming, study finds -- Science Daily
November 15, 2008: Milagro
detects cosmic ray hot spots -- University of Maryland
November 19, 2008: UM-conceived
experiment finds mysterious cosmic radiation -- University of
Maryland
November 19, 2008: Electron
'bump' may confirm dark matter -- Nature
November 19, 2008: Discovered:
Cosmic rays from a mysterious, nearby object -- Science@NASA
November 19, 2008: Dark
matter proof found over Antarctica? -- National Geographic
November 18, 2008: New eyes on
the cosmic-ray sky -- Sky & Telescope
November 14, 2008: Solar
cycle variations in observed galactic cosmic ray composition --
ACE News
November 13, 2008: Scientists
inaugurate world's largest cosmic-ray observatory -- Fermilab
November 4, 2008: PAMELA
bares all -- Physics World
October 30, 2008: Hot
solar wind in cold outer space -- The Weather Channel
September 30, 2008: The
'magnificent seven' of European astroparticle physics unveiled to the
world -- Science Daily
September 23, 2008: Ulysses
spacecraft data indicate Solar System shield lowering -- ESA
September 23, 2008: Solar
wind loses power, hits 50-year low -- Science@NASA
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
![IMAGE magnetosphere](image_mag_stamp.jpg)
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