vocabulary 10 galaxies and beyond

Galaxy  a large group of stars held together by gravity .

Milky wave  our home galaxy .

Spectrum   band of colors made when  light is broken out .

Expansion redshift   the shift of a spectrum of galaxy toward longer waveleght due to the expansion of space .

Big bang   the beginnig of the universe when the density of the universe was very hight .

Backgroud radiation   electromagnetic radiation left over from the big bang .

Quasar  an extremely bright extremely distance hight energy source .