| A | B |
|---|
| electromagnetic radiation | The energy transferred through space by electromagnetic waves. |
| spectrum | The range of wavelengths of electromagnetic waves. |
| refracting telescope | A telescope that uses convex lenses to gather and focus light. |
| reflecting telescope | A telescope that uses a curved mirror to collect and focus light. |
| parallax | The apparent change in position of an object when seen from different places. |
| scientific notation | A mathematical method of writing numbers using powers of ten. |
| spectograph | An instrument that separates light into colors and makes an image of the resulting spectrum. |
| apparent brightness | The brightness of a star as seen from Earth |
| absolute brighteness | The brightness a star would have if it were at a standard distance from Earth. |
| main sequence | A diagonal area on an Hertzsprung-Russell diagram that includes more than 90 percent of all stars. |
| nebula | A large cloud of gas and dust in space. |
| protostar | A contracting cloud of gas and dust with enough mass to form a star. |
| white dwarf | The blue-white hot core of a star that is left behind after its outer layers have expanded and drifted out into space. |
| supernova | The brilliant explosion of a dying supergiant star. |
| neutron star | The small, dense remains of a high-mass star after a supernova. |
| pulsar | A rapidly spinning neutron star that produces radio waves. |
| spiral galaxy | A galaxy with a bulge in the middle and arms that spiral outward in a pinwheel pattern |
| elliptical galaxy | A galaxy shaped like a round or flattened ball, generally containing only old stars. |
| quasar | An enormously bright, distant galaxy with a giant black hole at its center. |
| hubble law | The observation that the farther away a galaxy is, the faster it is moving away. |
