Galaxies

The Milky Way galaxy as seen from Earth’s surface.

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

There are 3 types of galaxies… Spiral Elliptical Irregular

3 Types of Galaxies 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 Spiral have arms of stars, gas , and dust that curve away from the center of the galaxy in a spiral pattern Ex. – Milky Way The process of galaxies colliding to create a larger galaxy is known as “galactic cannibalism.” Images taken from: http://school.discoveryeducation.com/schooladventures/universe/galaxytour/toknow.html

Spiral Galaxies

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.

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

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

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.