The Milky_Way is a spiral galaxy. There are various types of galaxies in the universe.
Spiral galaxies consist of a nucleus, a number of spiral arms aligned on a plane and a halo, which may contain a globular_star_cluster. Apart from old stars, these galaxies contain huge quantities of dust and molecular particles from which new stars are formed. Spiral galaxies are classified according to their size and the curvature of their spiral arms.
There are, however, various other types of galaxies, such as barred spiral galaxies. They have two widely open arms and defined nuclei. This nucleus is intersected by a band or bar, which extends outwards to the arms.
Elliptical galaxies can be spherical or elongated, giving them the appearance of a huge boat-hull. Their dimensions and the number of stars they contain often far exceed those of the Milky Way. Elliptical galaxies contain mainly old stars, with few new stars and little dust or gas.
Irregular galaxies have no distinct shape. They also contain vast areas of gas and dust as well as new stars, but have no consistent configuration. It is thought that the gravitational_pull of other large and nearby galaxies may be the cause for this.
