click below
click below
Normal Size Small Size show me how
Astronomy Galaxies
| Term | Definition |
|---|---|
| Galaxy | A system of stars, dust, gas and other planetary objects held together by gravity. |
| Spiral Galaxy | A galaxy in which the stars, gas clouds, and dust are concentrated mainly in one or more spiral arms. |
| Elliptical Galaxy | A galaxy with an ovoid or elliptical shape and does not have an apparent internal structure or spiral arms |
| Protogalactic Clouds | Areas of hydrogen and helium gas particles that formed during the early expansion of the universe. |
| Redshift | A shift toward longer wavelengths of the spectral lines emitted by a celestial object that is caused by the object moving away from the earth. |
| Lightyear | A unit of astronomical distance equivalent to the distance that light travels in one year, which is 9.4607 x 1012 km (nearly 6 trillion miles) |