Keywords+and+Definitions

__** KEYWORDS AND DEFINITIONS **__ solar system, astronomy,International Space Station, NASA, space,exploration, universe,space probe, astronaut,cosmos  planets, Mars, Earth, Venus, Mercury, Jupiter, Saturn, Uranus and Neptune **__ Glossary __** __asteroids__- small, rocky or metal space objects that orbit the Sun __astronomers__ -people who study stars, planets and other bodies in space __atmosphere__ the layer of gases that surrounds a planet, moon or star __Bureau of Meteorology__ -a government agency that provides weather information __carbon dioxide-__ an invisible gas that is produced when humans and animals breathe __comets__ - small, rocky and icy space objects that have long, shining tails that appear when orbiting near the Sun __dwarf planet__- a space object that is not quite big enough to be a planet but is too big to be an asteroid __fossil fuels__ - substances that formed in the Earth’s crust from the remains of plants and animals that lived millions of years ago, and which produce energy when burned (such as coal, oil and natural gas) __friction__ -a force that is created when one surface or object rubs against another, creating resistance gas -a substance that is not solid or liquid, and is usually invisible __gravitational pull__ -the forces of gravity that attract two objects towards each other __gravity__ -the force -that attracts all objects towards each other __impact craters__ -large, round holes made by a small space object crashing into a larger one __matter__ -a substance of a particular kind, such as gas and dust __meteorites__ -meteoroids that reach Earth’s surface without burning up completely meteoroidssmall space objects that are made of rock and metal, ranging from metres wide to the size of a pea __meteors__ -meteoroids that have entered Earth’s atmosphere and burn up __nebula__ -a cloud of gas and dust in space nucleusthe core or centre of an object oxygenan invisible gas produced by plants that makes up about 20 per cent of Earth’s atmosphere and makes air breathable __ozone layer__ -a band of gas found within the stratosphere and which absorbs many of the Sun’s harmful rays satellites -natural or human-made objects that orbit, or travel around, a planet __solar system__ the Sun and everything that orbits around it, including planets and other space objects __space__ -the area in which the solar system, stars and galaxies exist, also known as the universe __telescope__ -an instrument with a single eye piece, for making faraway objects look bigger tonnesa unit of measurement for weight; 1 tonne is equal to approximately 1000 kilograms __ultra-violet__ invisible rays that are a part of sunlight and which can be harmful (UV) rays to human eyes and skin in large amounts __water vapour__ tiny particles of water that are no longer a liquid and can be carried in the air __wavelength__ the waves in which light and sound travel; different types of sounds and colours have waves of different lengths
 * __meteoroid__** a trail of rocks and dust that follows a comet, forming the comet’s tail stream
 * __orbit__** the path taken by a space object that travels around another, larger one