Space

• Planets


  Large heavenly bodies that orbit a star
• Elliptical


  The oval shape of the path taken by many heavenly bodies as they orbit the Sun
• Asteroids


  Lumps of rock up to about 1000 km diameter, found in a 'belt' between Mars and Jupiter
• Comets


  Heavenly bodies made of mostly ice and dust that orbit a star, often in very elongated elliptical paths
• Solar System


  Consists of a star and everything that orbits it
• Moons


  • Natural satellites of planets that orbit planets
• Artificial satellites


  • Put into orbit around the Earth, used for astronomy, communications, weather monitoring, monitoring agricultural land use, monitoring military activity, and general espionage
• Stellar nebula


  Cloud of gas and dust from which stars are formed
• Gravitational collapse


  Process in the evolution of a star in which hydrogen particles get closer and closer together because of gravity
• Protostar


  Very, very hot ball of gas in which nuclear fusion has not yet begun
• Main sequence


  Most stable stage in the mid-life of a star
• Red giant


  Star that has used up almost all of its hydrogen and the outward pressure from nuclear fusion makes it expand to several hundred times its normal size
• White dwarf


  One of the last stages in the life cycle of a star like our Sun
• Black dwarf


  Final state of a star, like our Sun, when all fusion stops and it becomes very cold
• Red supergiant


  Stage in the life cycle of a very massive star following the main sequence stage
• Supernova


  Stage near the end of the life cycle of a very massive star when it suddenly increases greatly in brightness because of a catastrophic explosion that ejects most of its mass
• Neutron star


  Collapsed core of a large star
• Black hole


  Collapsed core of a very large star, with such enormous gravitational fields that nothing can escape from them, not even light
• During a period of gravitational collapse, the hydrogen nebula that eventually forms a protostar starts to spin. It is generally thought that this spinning disc of gas and dust is 'blowing off' the excess angular momentum
• Our Solar System comes from a galaxy, the Milky Way, which is one of billions of galaxies in the universe
• Most physicists think the universe began with the Big Bang, which occurred around 13.8 billion years ago
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