Asteroids: Small rocky objects in the solar system, ranging in size from dust particles to around 1,000 km across.

Asteroid Belt: The region of the solar system where we find the majority of asteroids, in a belt between the orbits of Mars and Jupiter.

Atom: The smallest part of a chemical element that has all the characteristics of that element. Made up of protons, neutrons, and electrons.

Bright Star: A star in the lengthy, stable, middle period of its life, which lasts about 10 billion years.

Comets: Smaller members of the solar system, made of ice, rock, and gas, that orbit the Sun.

Constellation: A pattern of stars as seen in the sky at has been given a name.

Core: The central region of a moon, planet or star. The energy of a star is produced in its core.

Eclipse: The total or partial blocking of light from a celestial body caused by its passing into the shadow of another body (as in a lunar eclipse), or the hiding of one celestial body by another (as in a solar eclipse).

Energy: The ability to do work. Motion, heat, light, and sound are all forms of energy.

K: stands for Kelvin, the absolute temperature used in astronomy. 0 K = -273 C. This is absolute zero.

Meteor:The streak of light caused by a meteoroid that passes through a planet's atmosphere. Also called a shooting star.

Meteorites: A piece of meteor large enough to have reached the Earth's surface. The largest found so far weighs 132, 000 pounds, and is located in southwest Africa.

Meteoroid: A solid body in orbit about the Sun, much smaller than an asteroid and usually weighing less than about 100 kilograms.

Moon (see also Satellite): A natural celestial body having a regular orbit around another larger body, such as a planet.

Nuclear fusion: The process by which heavier atomic nuclei are built from lighter ones, releasing great amounts of energy in the process.

Nucleus: the central part of an atom, containg protons and neutrons. Electrons revolve around the nucleus.

Orbit: The path followed by a body moving around another body. For example, our Moon is in orbit around the Earth, and the Earth is in orbit around the Sun.

Planetary nebula: A shell of glowing gas surrounding a star that was ejected from that star.

Protostar: The original material from which a star will develop when the hydrogen fusion process starts.

Red Giant: A large, luminous star with a coll surface, and therefore red in colour.

Ring: An orbiting stream of large and small particles around a planet. Four planets in our solar system have rings: Jupiter, Saturn, Uranus, and Neptune. We do not yet know if Pluto has rings.

Satellite (see also moon): A natural or artificial body having a regular orbit around a larger body.

Solar system: The collection of planets, moons, asteroids, comets, and other chunks of rock that circle our Sun.

Solar Wind: A stream of electrically charged particles from the Sun.

Star: A hot, glowing sphere of gas, usually one that emits energy from nuclear reactions in its core.

Sunspot: A magnetic disturbance on the Sun. It is cooler than the surrounding area and, consequently appears darker.

Universe: All matter and energy, and the space in which they are found.

White Dwarf: A small, hot star near the end of its nuclear fusion period.