Planetary science Reference Libraries

Page 3 of about 52 Articles
2004-10-19 04:45:41

Crater -- A crater is a circular depression on the surface of a planet, moon, asteroid, or other celestial body. Craters are typically caused by meteorite impacts, although some are caused by volcanic activity. In the center of craters on Earth a crater lake often accumulates, and in craters formed by meteorites a central island (caused by rebounding crustal rock after the impact) is...

2004-10-19 04:45:41

Aurora -- The Polar Aurora are natural displays of light in the sky that can be seen with the unaided eye only at night. An auroral display in the Northern Hemisphere is called the aurora borealis, or the northern lights; in the Southern Hemisphere it is called the aurora australis. Auroras are the most visible effect of the sun's activity on the earth's atmosphere. The beautiful and often...

2004-10-19 04:45:41

Asteroid -- An asteroid, also called a minor planet or planetoid, is a member of a group of small, planet-like bodies that are part of our solar system. They are believed to be remnants of the interstellar clouds, nebula, that were not incorporated into planets during the formation of the solar system. The largest asteroid in the inner solar system is Ceres with a diameter of 1003 km. It...

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...

Solar Wind
2004-10-19 04:45:41

Solar Wind -- Solar wind, a stream of particles (mostly high-energy protons ~ 500 Kev) that is continually ejected from the surface of the Sun. The composition of this plasma is identical to the Sun's corona, 73% hydrogen and 25% helium with the remainder as trace impurities, and is ionized. Near Earth, the velocity of the solar wind varies from 200km/s-889km/s. The average is 450 km/s....

Solar System
2012-10-22 06:09:41

The Solar System refers to the area in space that is dominated by our own Sun. It is comprised of the Sun and its associated astronomical objects that are held in its gravitational orbit. The Solar System was formed as a result of the collapse of a giant molecular cloud approximately 4.6 billion years ago. The mass of this system is located almost entirely in the Sun. Apart from the Sun, a high...

Solar Maximum
2004-10-19 04:45:41

Solar Maximum -- The Sun, a roiling ball of plasma, occupies its place in space approximately 93 million miles from Earth. Though it seems simple to inhabitants of this planet -- the Sun shines, giving light and heat -- the processes occurring in the Sun are so complex that many scientists devote their careers to just one aspect of solar activity. Changes in the activity of the Sun...

Solar Flare
2004-10-19 04:45:41

Solar Flare -- A solar flare is a violent eruption that explodes from a star's photosphere with energies equivalent to tens of millions of hydrogen bombs. Solar flares from the Sun send out a streams of highly energetic solar wind that can present a radiation hazard to spacecraft outside of planetary magnetospheres and can disrupt radio signals on Earth. Solar flares were first observed...

2004-10-19 04:45:41

Quaoar -- Quaoar ("kwah-oh-ahr", /kwA o Ar/) is a Trans-Neptunian object circling the Sun in the Kuiper belt, discovered in 2002 by astronomers Chad Trujillo and Mike Brown at the California Institute of Technology in Pasadena, California. Quaoar is estimated to have a diameter of about 1,280 kilometres, which would make it the largest Solar System object discovered since Pluto and, indeed,...

Oort Cloud
2004-10-19 04:45:41

Oort Cloud -- The Oort cloud is a postulated cloud of comets situated about 50,000 to 100,000 AU from the sun. Although no direct observations have been made of such a cloud, it is believed to be the source of most or all comets entering the inner solar system (some short-period comets may come from the Kuiper belt), based on observations of the orbits of comets. The Oort cloud was...

Word of the Day
  • A small crescent-shaped structure or marking, especially the white area at the base of a fingernail that resembles a half-moon.
This word is a diminutive of the Latin 'luna,' moon.