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Last updated on April 20, 2014 at 8:28 EDT

Physics Reference Libraries

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Accelerating Universe
2004-10-19 04:45:41

Accelerating universe -- In the late 1990s, observations of type I supernova produced the unexpected result that the expansion of the universe appears to be accelerating. These observations appear more firm as new data has appeared. This means that the speed with which a distant galaxy recedes from us increases over time. If this trend continues, eventually we won't be able to see any...

Van Allen Radiation Belt
2004-10-19 04:45:41

Van Allen Radiation Belt -- The Van Allen radiation belt is a torus of energetic charged particles around Earth, trapped by Earth's magnetic field. The presence of a radiation belt had been theorized prior to the Space Age and the belt's presence was confirmed by the Explorer I on January 31, 1958 and Explorer III missions, under Doctor James Van Allen. The trapped radiation was first mapped...

The Sun
2004-10-19 04:45:40

The Sun -- intensely hot, self-luminous body of gases at the center of the solar system. Its gravitational attraction maintains the planets, comets, and other bodies of the solar system in their orbits. The sun is actually a star of about medium size; it appears larger than the other stars because of its relative nearness to the earth. The earth's distance from the sun varies from 91,377,000...

Supernova 1987a
2004-10-19 04:45:40

Supernova 1987a -- Supernova 1987a was a supernova in the Large Magellanic Cloud, a nearby dwarf galaxy. It occurred approximately 50 kiloparsecs from Earth, the closest supernova since Supernova 1604, which occurred in the Milky Way itself. The light from the supernova reached Earth on February 23, 1987. Its brightness peaked in May with a magnitude of about 3 and slowly declined in...