Galaxies
A galaxy is a large group of stars, gas, and dust held together by gravity. The galaxy in which Earth is found is called the Milky Way. Galaxies are separated by huge distances, often millions of light years. Their are three types of galaxies: spiral, elliptical, and irregular.
Spiral Galaxies
The Milky Way is a spiral galaxy. S[iral galaxies have spiral arms that wind outward from inner regions. These arms are made up of bright stars and dust. The fuzzy patch seen in the constellation of Andromeda is a spiral galaxy. It is so far away that you cannot see its individual stars. Instead, its combined light appears as a hazy spot in the sky. The Andromeda Galaxy is about 2 million light-years away and is a member of the Local Group.
Arms in a normal spiral start close to the center of the galaxy. Barred spirals have spiral arms extexding from a large bar of stars and gas that passed through the center of the galaxy.
Arms in a normal spiral start close to the center of the galaxy. Barred spirals have spiral arms extexding from a large bar of stars and gas that passed through the center of the galaxy.
Elliptical Galaxies
A common type of galaxy is the elliptical galaxy. These galaxies are shaped like large, three-dimensional ellipses. Many are football shaped, but others are round. Some elliptical galaxies are small, while others are so large that several galaxies the size of the Milky Way would fit inside one of them.
Irregular Galaxies
The third type, an irregular galaxy, includes most of those galaxies that do not fit into the other classifications. Irregular galaxies have many different shapes. They are smaller than the other types of galaxies. Two irregular galaxies called the Cloud of Magellan orbit the Milky Way.