10.2 Galaxies

Our star, the sun, is one

of 100 - 400 billion stars in the Milky Way galaxy, and there are 125 billion galaxies in the universe!

See pages 356 - 360

A galaxy is a large group of stars.

A nebula is a cloud of gas and dust in space that often produces a new star, or is the remains of an old star.

http://en.wikipedia.org/wiki/Nebula

Galaxies can be spiral, elliptical or irregular in shape.

How fast a galaxy spins helps define its shape.

The Milky Way is a barred spiral galaxy some 100,000–120,000 light-years in diameter which contains 100–400 billion stars. It may contain at least as many planets as well.[20]

[21] The Solar System is located within the disk, about 27,000 light-years away from the Galactic Center, on the inner edge of a spiral-shaped concentration of gas and dust

called the Orion–Cygnus Arm. http://en.wikipedia.org/wiki/Milky_Way

The Milky Way is the galaxy that contains our Solar System. This name derives from its appearance as a dim “milky” glowing band arching across the night sky, in which the naked eye cannot distinguish individual stars.  The Milky Way appears like a band because it is a disk-shaped structure being viewed from inside.

http://sciencepenguin.com/milky-way-galaxy/

Each galaxy has stars clustered as globular clusters or open clusters.