galaxies are collections of stars (between 200 billion and 400 billion) that all rotate (orbit)...

Galaxies

Galaxies are collections of stars

(between 200 billionand 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 seenfrom Earth’s surface.

Our Galaxy

We are locatedabout 2/3 of the way out fromthe galactic core.

3 Types of Galaxies

Spiralhave arms of stars, gas , and dust that curve away

from the center of the galaxy in a spiral pattern

Ex. – Milky Way

Ellipticalshaped like spheres or eggs; have

almost no dust or gas between stars; contain

old stars

Irregularfaint 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 knownas “galactic cannibalism.”

Images taken from: http://school.discoveryeducation.com/schooladventures/universe/galaxytour/toknow.html

1. Spiral Arms

The armscontaingas, dustand stars.

The arms rotatearound the galactic core.

2. The Galactic Plane

Spiral galaxiesform a flatrotating diskof material.

Side View

Galactic Plane

3. The Galactic CoreThe core of the galaxy is wheremost of the starsare found. It isvery bright and is an intense sourceof x-rays and radio waves.

3. The Galactic Core

3. The Galactic Core

Our solar system orbitsaround the galactic core.It takes 250 million yearsfor us to make one complete orbit.

Why can’t we see the galactic core verywell ???

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

Dark gasand 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.

Ellipticalgalaxiescontainalmost NO gas or dust.They onlyhave stars inthem.

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 irregularshape. No two are exactly alike.

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