| A | B |
|---|
| constellation | A pattern of stars in the sky. |
| visible light | Electromagnetic radiation that can be seen with the unaided eye. |
| electromagnetic radiation | Energy that travels through space in the form of waves. |
| wavelength | The horizontal distance between two wave crests. |
| spectrum | The range of wavelengths of electromagnetic waves. |
| refracting telescope | A telescope that uses convex lenses to gather and focus light. |
| convex lens | A piece of transparent glass curved so that the middle is thicker than the edges. |
| reflecting telescope | A telescope that uses one or more mirrors to gather light. |
| radio telescope | A deviice used to detect radio waves from objects in space. |
| observatory | A building that contains one or more telescopes. |
| spectrograph | An instrument that separates light into colors and photographs the resulting spectrum. |
| pulsar | A nutron star that produces radio waves. |
| nebula | A large amount of gas and dust in space, spread out in an immense volume. |
| protostar | A contracting cloud of gas and dust;the earliest stage of a star's life. |
| white dwarf | The remaining hot core of a star after its outer layers have expanded and drifted out into space. |
| supernova | The explosion of a dying giant or super giant star. |
| neutron star | A tiny star that remains after a supernova explosion. |
| black hole | The remains of an extremely massive star pulled into a small volume by the force of gravity. |
| quasar | A distant galaxy with a black hole at its center. |
| binary star | A star system that contains two stars. |
| eclipsing binary | A star system in which one star periodically blocks the light from another. |
| spiral galaxy | A galaxy whose arms curve outward in a pinwheel pattern. |
| elliptical galaxy | A galaxy shaped like a flattened ball, containing only old stars. |
| irregular galaxy | A galaxy that does not have a regular shape. |
| big bang | The initial explosion that resulted in the formation and expansion of the universe. |
