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WORD MEANING EXTRA INFORMATION

A.S.I. Agenzia Spaziele Italiana - The Italian Space Agency.  
Accretion The build-up and accumlation of matter (dust and gas) which results in the formation of stars, planets, moons and other objects in solar systems.  
Adams, John Couch When he was 24, English astronomer and mathematician John Adams was the first to predict the location of an object beyond the orbit of Uranus. This object was later found by German astronomer Johann Gottfried Galle in 1646 and became known as Neptune. Galle used predictions of its location by French astronomer Urbain Jean Joseph Le Verrier since Adams didn't publish his findings! Adams lived from 1819 to 1892.  
Adrastea Moon of Jupiter, discovered in 1979 by Voyager, 2nd closest moon to Jupiter, diameter 40 km (25 miles)  In mythology, Adrastea was the daughter of Jupiter and Ananke and the distributor of punishments and rewards. 
Aegir moon of saturn  
Aitne Moon of Jupiter, discovered in 2003 by a group of astronomers at the University of Hawaii. It is irregularly shapes with a diameter of about 4 km (2 and a half miles). It orbits the planet at a distance of 23,981,000 km (14,901,100 miles).  
Albiorix moon of saturn  
Aldrin, Edwin "Buzz" Apollo 11 astronaut. Second man to walk on the Moon's surface.  
Alpha Centauri The 3rd nearest star to Earth, after the Sun and Proximus Centauri. 4.4 light years away. Also the fourth brightest star in the sky, after the Sun, Sirius and Canopus, with a magnitude of -0.3.  
Aoede moon of jupiter  
Aphelion The greatest distance of a planet or comet in its orbit around the Sun. Opposite to perihelion.   
Apoapsis The greatest distance of a body (a moon or an artificial satellite) in its orbit around bodies other than the Sun or Earth (for example, a moon around Jupiter).  
Apogee The greatest distance of a body (the Moon or an artificial satellite) in its orbit around Earth.   
Apollo Name given to missions in the 1960s and 1970s designed to land man on the Moon and return him home. Three astronauts testing Apollo 1 died in a fire in the capsule. Apollo 4 - 6 were unmanned launches. Apollo 7 was a manned launch but didn't go to the Moon. Apollo 8 - 10 were manned launches to the Moon (but were not designed to land). Apollo 11 - 17 were manned missions to land on the Moon. No moon landing took place during Apollo 13 due to an explosion onboard.  
Amalthea Moon of Jupiter, discovered in 1892 by Edward Emerson Barnard. 200 km (150 miles) in diameter. In mythology, Amalthea was a nymph who nursed a young Jupiter with goat's milk.
Ananke moon of jupiter  
Anthe Moon of Saturn  
Arago, Dominique François Jean French astronomer and physicist. He discovered the production of magnetism by rotation. He was also director of the Paris Observatory and lived from 1786 to 1853.  
Arcturus Fifth brightest star in the sky, 36 light years from Earth, magnitude 0.0  
Arche moon of jupiter  
Ariel moon of uranus  
Armstrong, Neil Apollo 11 astronaut. First man to walk on the Moon's surface.  
d'Arrest, Heinrich Louis Danish astronomer involved in the first observation of the planet Neptune. He was assisting German astronomer Galle who was using information provided by French mathematician Le Verrier about the position of an object beyond Uranus. While Galle observed the sky, d'Arrest read from a star chart. Galle spotted an object which wasn't listed on d'Arrest's chart, and the first observation of Neptune was made! D'Arrest lived from 1822 to 1875.  
Asteroid Medium-sized rock fragments left over from the formation of the Solar System left to float around space. Smaller than planets but larger than meteoroids. Also known as "Planetoids"  
Asteroid Belt Region in between the orbits of Mars and Jupiter where a large number of asteroids orbit the Sun.  
Asteroid Number Each asteroid discovered is given a number based on the order that it was discovered. 1 Ceres means that Ceres was the first asteroid to be discovered. 4 Vesta means that Vesta was the fourth asteroid to be discovered.   
Astronaut A person who travels into space. Russia/Soviet equivalent is Cosmonaut.  
Astronomical Unit A unit of measurement used for measuring distances in space. 1 A.U. is equal to the approximate distance from the Earth to the Sun (150 million kilometres).   
Astronomy The study of the objects in the sky, eg: stars, planets, moons, galaxies, comets, asteroids, etc.  
Astrology The belief that the positions of the Sun, Moon, stars and planets can affect a person's destiny.  
Atlas Moon of Saturn  
Atmosphere The layer of gas surrounding the surface of a planet, moon or star.  
Atom A tiny particle of matter, itself made up of many particles of matter.  
Aurora Glowing lights in the sky caused by the interaction between the Solar Wind (charged particles from the Sun) and a planet's magnetic field.  
Aurora Australis An aurora which can be seen in the Southern Hemisphere. The glowing lights are caused by the interaction of charged particles from the Sun and Earth's magnetic field in the upper atmosphere (or ionopshere). Also known as the "Southern Lights"  
Aurora Borealis An aurora which can be seen in the Northern Hemisphere. The glowing lights are caused by the interaction of charged particles from the Sun and Earth's magnetic field in the upper atmosphere. Also known as the "Northern Lights"  
Autonoe moon of jupiter  
Axis The imaginary line around which a planet, moon, star spins.  

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