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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Asteroid: a small round object made of rock and metal that orbits in the Solar System between Mars and Jupiter. Big Bang: an event that astronomers believe happened some 15 000 million years ago which created the Universe. Black hole: a region in space that has such an enormous gravity that not even light rays can escape. Comet: a tiny member of the Solar System, which starts to shine when it draws near to the sun. Constellation: the pattern a group of bright stars make in the sky. Docking: the joining together of two spacecraft in space. Eclipse: the movement of one heavenly body across the face of another, An eclipse of the Sun takes place when the Moon moves across the face of the Sun and blots out its light. Galaxy: a great star 'island' in space. All stars in the Universe gather together in galaxies. Gravity: the pull of the Earth on everything on it or near it in space. Every heavenly body has a similar pull. The bigger the body, the stronger is the gravity, or gravitational pull. Hydrogen: the most plentiful substance in the Universe. It is the 'fuel' stars use to produce the energy to shine. Light-year: the distance light travels in a year, nearly 10 million million kilometres. Astronomers use the light-year as a unit to measure the instance to the stars. Meteor: a fiery streak in the night sky, produced when a meteoroid burns up in the Earth's upper atmosphere. Meteorite: a piece of rock from outer space that does not burn up in the atmosphere like a meteor, but hits the ground. Meteoroid: a bit of rocky matter that travels through space. Milky Way: the fuzzy white band of light that arcs across the heavens. It is also the name of our Galaxy, to which the Sun and the stars in the sky belong. Moon: another term for satellite. NASA: the National Aeronautics and Space Administration; the body that organises space activities in the United States. Nebula: a bright or dark 'cloud' of gas and dust among the stars. Orbit: the path taken when one body circles around another in space. Phases: the changes in appearance of the moon during the month, as we see more or less of it lit up by the Sun. Planet: a large body that orbits around the Sun. The Earth is one of nine planets. Probe: a spacecraft that escapes from the Earth and travels far into space to explore the planets and other bodies. Rocket: an engine that is propelled by a stream of gases escaping from the rear at high speed. Satellite: a small body that circles around a larger one in space. Most planets have natural satellites: the Earth has one natural satellite (the Moon) and also many man-made satellites. Solar: to do with the Sun Solar System: the family of the Sun, which includes the planets and their moons, asteroids, meteoroids and comets. Space: the great emptiness through which the planets, Sun, stars and galaxies travel. Star: a great globe of hot gas, which gives out energy as light, heat and other forms of radiation. Stellar: to do with stars. Terrestrial: to do with the Earth. UFO: unidentified flying object: a mysterious object seen in the sky, which no one can explain. Some people believe that UFO's come from another world. Universe: everything that exists: the Earth, the planets, the Sun, the stars and space. Weightlessness: the strange state that exists in orbit, where nothing appears to have any weight. The correct term for it is free fall. |
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