Astronomy 451Chapter 1

Our Place in the Universe

Universe supercluster clusters (make up local group) Milky Way solar system Earth

http://youtu.be/17jymDn0W6U

Universe

• The universe can be define as the sum total of all the matter and energy (all galaxies and everything in between them).

• thought to have begun with a physical event scientists refer to as the Big Bang

Supercluster

• a gigantic region of space comprised of clusters of galaxies

• largest structures of the universe

• ~ 110 million light-years across

Cluster

• collection of galaxies bound together by gravity

• Smaller collections of galaxies are called groups (a subdivision of a cluster)

• The Milky way is located in the Local Group which contains about 50 galaxies.

Clusters contain anywhere from a few hundred to a few thousand

galaxies.

Galaxies

• collection of stars ranging from a hundred million to a trillion or more

• Milky Way Galaxy contains about 300 billion stars

Galaxies

4 main types

1. spiral2. bared spiral

3. elliptical4. irregular

Galaxies1. Spiral

constantly rotating2. Barred Spiral

Milky Way100 billion starsdiameter – 100,000 light yrs

3. Ellipticalvery commonold, dim galaxies lacking spirals

4. Irregularleast common, has no distinct regular

shape

Name that type of galaxy!

Barred Spiral

Spiral

Elliptical

Irregular

%age of 4 Galaxy Types

SpiralEllipticalIrregularBarred Spiral

~ 60%

At the Bell AssignmentComplete in Notes

1. The most common type of galaxy is the A. barred spiral B. spiral C. elliptical D. irregular

2. The Milky Way Galaxy is consideredA. barred spiral B. spiral C. elliptical D. irregular

3. A collection of stars ranging from millions to billions is a A. cluster B. supercluster C. galaxy D. energy

4. The sum of all energy and matter we can observe is called the A. supercluster B. universe C. dark matter D. cluster

5. When we observe distant stars, we are actually looking back in tim. TRUE or FALSE

The Big Bang and Expanding Universe

• Our universe began with the Big Bang and has been expanding (growing in all directions) ever since.

NASA Big Bang