Vocabulary #11 (Galaxies and beyond)

Definitions:

1. galaxy: a large group of stars held together by gravity
2. Milky Way: our home galaxy
3. spectrum: a band of colors made when white light is broken up
4. expansion redshift: the shift of a spectrum of a galaxy toward longer (redder) wavelenghts due to the expansion of space
5. Big Bang: the beggining of the universe, when the density of the universe was very high
6. background radiation: electromagnetic radiation left over from the big bang
7. quasar: an extremely bright, extremely distant, high energy source

Sentences and illustrations

1. Our closer galaxy is the Andromeda galaxy.

2. The Milky Way is a spiral galaxy.

3. The heated gases of stars produce waves of light, this light produces a spectrum.

4. The expansion redshift is called redshift because the light's spectrum has been shifted to longer wavelenghts.

5. The universe has expanded ever since the big bang.

6. The background radiation is energy left over from the beggining of the universe.

7. Quasars have the size aproximately of the solar system.