Astronomy 451 Chapter 1 Our Place in the Universe

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

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. spiral 2. bared spiral 3. elliptical 4. irregular

Galaxies 1.Spiral constantly rotating 2.Barred Spiral Milky Way 100 billion stars diameter – 100,000 light yrs 3.Elliptical very common old, dim galaxies lacking spirals 4.Irregular least common, has no distinct regular shape

Name that type of galaxy! Barred Spiral

Spiral

Elliptical

Irregular

%age of 4 Galaxy Types

At the Bell Assignment Complete in Notes 1. The most common type of galaxy is the A. barred spiralB. spiral C. ellipticalD. irregular 2. The Milky Way Galaxy is considered A. barred spiralB. spiral C. ellipticalD. 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. superclusterB. universe C. dark matterD. 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