| A | B |
|---|
| vacuum | an area not filled by molecules of matter |
| wavelength | distance from the crest of one wave to the crest of the following wave |
| friction | the force that resists motion |
| frequency | number of waves that pass a given point in a unit of time |
| gravity | the force of attraction that exists between any two objects |
| astronomy | the study of outer space and all that it contains |
| oscillation | any motion that repeatedly follows the same path |
| trough | low point of a wave |
| wave | movement of energy from one place to another |
| crest | high pont of a wave |
| blue | hottest star |
| red | coolest star |
| yellow | our sun is... |
| Sirius | brightest star in the night sky |
| Proxima Centauri | star closest to the sun |
| nova | faint star that flares suddenly to many times it orginal brightness |
| spiral galaxy | shape of the Milky Way |
| Polaris | pole star in the Northern Hemisphere |
| galaxy | large cluster of stars held together by the gravitational attraction |
| photosphere | visible part of the sun |
| sunspots | dark patches on the sun's photosphere |
| corona | hot vapor blanket surrounding the chromosphere |
| dispersion | separation of white light into the colors of the spectrum |
| reflection | occurs when waves hit an obstacle and tur aside or turn back |
| 186,000 | light travels at this speed |
