Glossary of the universe

Asterism    : Small, easily-recognized pattern of stars, usually forming part of a larger pattern, or constellation.
Asteroid    : Small, rocky object orbiting the Sun. Thousands of them exist in the part of the Solar System known as the Asteroid Belt, between Mars and Jupiter.
Astronomy: The scientific study of the universe and the objects in it.
Atmosphere : A layer of gas that surrounds a planet or star.
Aurora : A display of light in the upper atmosphere near a planetís poles. Caused by solar wind.
Big Bang : Theory A theory which states that the universe began in an enormous explosion.
Binary star : Two stars that revolved around one another, locked together by each otherís gravity.
Black hole : An invisible region in space that has an enormous pull of gravity. Caused by a collapsed super giant star.
Cataclysmic variable : A type of binary star system where, from time to time, one star gains some of the other starís matter. As this happens, a huge amount of light is given off.
Cluster : A group of stars or galaxies that lie close together.
Coma : The huge cloud of gas around the icy nucleus of a comet.
Comet : A chunk of dirty, dark ice, mixed with dust and grit which revolves around the Sun in an oval orbit.
Constellation : A group of stars that can be seen as a pattern from Earth. There are 88 constellations.
Core : The central part of a planet, moon or asteroid. It is made of different materials from its surrounding layers.
Corona : The outermost part of the Sunís atmosphere.
Crater : A hollow in the surface of a planet, moon or asteroid, caused by the impact of a meteorite or an asteroid.
Crust : The outer part of a planet or moon, made mostly of rock.
Day : The length of time it takes a planet to spin around once.
Dwarf star : A star which is smaller than the Sun.
Eclipse : The total or partial blocking of one object in space by another. For example, when the Moon passes in front of the Sun, the Sun is eclipsed.
Eclipsing variable : A type of binary star, where one of the stars passes in front of the other, resulting in a dip in brightness.
Equator : The imaginary line around the middle of a planet, dividing its northern hemisphere from its southern hemisphere.
Facula : A cloud of glowing gases that surrounds a sunspot, hovering just above the Sunís surface.
Galaxy : A group of stars, nebulae, star clusters, globular clusters and other matter. There are millions of galaxies in the universe.
Gas giant : A type of planet which is made up of gas and liquids surrounding a relatively small core.
Giant star : A star which is larger than the Sun.
Gravity : The force of attraction that pulls a smaller object toward a more massive object. For example, the Moon is attracted to the Earth by gravity.
Hemisphere : Half of a planet or moon. The top half is the northern hemisphere and the bottom half is the southern hemisphere.
Light year : The distance that a ray of light travels in one year : 9.46 million million km.
Magnitude A starís brightness
Matter : tiny particles from which everything is made.
Meteor : A meteoroid that travels through the Earthís atmosphere. As it falls toward Earth, it burns up, making a streak of light. Also known as a shooting star.
Meteorite : A meteor that hits the Earthís surface.
Meteoroid : Dust or a small chunk of rock which orbits the Sun.
Meteor : shower A short but spectacular display of meteors caused by the Earth moving across the orbit of a comet.
Milky Way : A broad band of light that looks like a trail of spilled milk in the night sky. Created by the millions of faint stars that form part of our galaxy.
Milky Way galaxy : The galaxy that contains the Solar System.
Moon : Any natural object which orbits a planet.
Moon : The ball of rock which orbits the Earth.
Multiple system : A star system containing two or more stars.
NASA : The National Aeronautics and Space Administration, which organizes space exploration on behalf of the government of the U.S.A. Projects includes the Space Shuttle missions.
Nebula : A vast cloud of gas and dust where new stars often form.
Neutron star : A small, spinning star that is left when a supergiant star has exploded.
Nova : A star that suddenly increases in brightness and then fades away. A type of cataclysmic variable star.
Nuclear fusion : A type of activity that goes on inside a star, where tiny particles (called atoms) of gas join together to make larger atoms. This process creates huge amounts of heat and light.
Nucleus : The central point around which other things are arranged. In astronomy, the word is used to refer to the dense part in the middle of a galaxy or at the head of a comet.
Optical double star : Two stars that appear very close together when seen from Earth, because they are in the same line of sight. However, they are not linked to one another in any way.
Orbit : The path of one object as it revolves around another. For example, the planets orbit the Sun.
Penumbra : An area of light shadow caused by the partial eclipse of one object by another.
Phase : A particular stage in a cycle of changes that occurs over and over again. For example, the Moonís appearance goes through several phases as it travels around the Earth every month.
Physical double star : Another name for a binary star.
Planet : A relatively large object that revolves around a star, but which is not itself a star. There are nine known planets in our Solar System.
Planetary nebula : Outer layers of gas from a dying star, which are puffed into space. From a distance, the layers of glowing gas around the dying star make it look like a planet.
Planisphere : A movable, circular map of the stars in the sky that can be made to show the appearance of the night sky at any given time and date.
Pointers : Two or more stars in a constellation that show the way to another constellation.
Pole : One of the two points on a planetís surface that are farthest away from its equator.
Primary star : The brighter star in an eclipsing variable
Prominence : A cloud of gas that bursts out from the Sunís surface.
Pulsar : A neutron star that sends out beams of radiation which swing around as the star spins.
Pulsating variable : A star which changes in size, temperature and brightness.
Radar : A method of finding the position and speed of distant objects using beams of radio waves.
Radiation : The waves of energy, heat or particles from an object.
Red giant : Type of star that has a relatively low temperature and is many times larger than the Sun.
Satellite : Any object in outer space that orbits another object. Manmade satellites are launched into space to orbit a planet or moon.
Secondary star : The fainter star in an eclipsing variable.
Shooting star : Another name for a meteor.
Solar : Something that relates to the Sun, such as a solar flare, or solar wind.
Solar flare : A sudden outburst of energy from a small part of the Sunís surface.
Solar System : The Sun and all the objects that orbit it.
Solar wind : A constant stream of invisible particles that is blown from the Sunís surface into space.
Spacecraft : A vehicle made to travel in space.
Space probe : An unmanned spacecraft which collects information about objects in space and sends it back to scientists on Earth.
Space shuttle : A spacecraft which carries people and materials into space. It is launched by a rocket but lands like a plane and can be used again.
Space station : A large, manned satellite in space used as a base for space exploration over a long period of time.
Spectral type : A class of star shown by the letters O, B, A, F, G, K and M.
Star : A ball of constantly exploding gases, giving off light and heat. The Sun is a star.
Sun : A medium-sized star that lies in the middle of our Solar System.
Sunspot : One of the dark patches that appear on the Sun every now and again.
Supergiant stars : The brightest giant stars. They live for only a few million years.
Supernova : The explosion of a supergiant star which generates enormous amounts of light. The star then collapses to form a neutron star, or if the star was very large, a black hole.
Tail : The stream of visible gases that comes off a comet as it passes relatively close to the Sun.
Umbra : An area of dark shadow caused by the eclipse of one object by another.
Universe : The word used to describe everything that exists in space, including the galaxies and stars, the Milky Way and the Solar System.
Variable star : A star whose brightness changes over time, usually in a predictable way.
White dwarf : A type of star that is much smaller and denser than the Sun. It gives off a relatively dim, white light.
Year : The length of time it takes a planet to orbit the Sun.