A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter. The word galaxy is derived from the Greek galaxias, literally "milky", a reference to the Milky Way.
Elliptical: These have a faint, rounded shape, but they're devoid of gas and dust, with no visible bright stars or spiral patterns. ...
Spiral: The Milky Way is one of the larger spiral galaxies. ...
Irregular: These are small, faint galaxies with large clouds of gas and dust, but no spiral arms or bright centers.
