Galaxies are collections of stars (between 200 billion and 400 billion) that all rotate (orbit) around a massive central point.

There are 3 types of galaxies… Spiral Elliptical Irregular

Our home galaxy is the Milky Way. Our galaxy as seen from Earth’s surface.

Our Galaxy We are located about 2/3 of the way out from the galactic core.

3 Types of Galaxies Spiral have arms of stars, gas, and dust that curve away from the center of the galaxy in a spiral pattern Ex. – Milky Way Elliptical shaped like spheres or eggs; have almost no dust or gas between stars; contain old stars Irregular faint galaxies without a definite shape; smaller than the other types of galaxies; contain fewer stars The process of galaxies colliding to create a larger galaxy is known as “ galactic cannibalism. ” Images taken from:

1. Spiral Arms The arms contain gas, dust and stars. The arms rotate around the galactic core.

2. The Galactic Plane Spiral galaxies form a flat rotating disk of material.

Side View Galactic Plane

3. The Galactic Core The core of the galaxy is where most of the stars are found. It is very bright and is an intense source of x-rays and radio waves.

3. The Galactic Core

Our solar system orbits around the galactic core. It takes 250 million years for us to make one complete orbit.

Why can’t we see the galactic core very well ???

Because of all the gas and dust in the way. It blocks our view just as fog or smoke would block your view on Earth. Dark gas and dust.

Barred Spiral Galaxies - They’re a type of spiral galaxy in which there are only two spiral arms. Can you see why how it got its name?

Elliptical Galaxies are you guessed it, they’re oval shaped.

Elliptical galaxies contain almost NO gas or dust. They only have stars in them.

Elliptical galaxies are also smaller than spiral galaxies and have no spiral arms.

But they do have a bright core with densely packed stars just like spirals. And they also have a core that emits x-rays.

The name pretty much says it all..

Irregular galaxies have an irregular shape. No two are exactly alike.

Irregular galaxies contain almost NO stars. They’re virtually all gas and dust.