CELESTIAL FORMATION
Galaxy A large collection of stars Galaxies contain star groups Galaxies only contain 1% of matter
in the universe The remaining 99% of matter in the
universe is “empty” space consisting of gases and dust
Milky Way Galaxy
The galaxy where we are located Contains 100 to 200 billion stars Also contains gas and dust clouds
(nebulae) Approximately 100,000 light years in
diameter and about 15,000 light years thick
Solar system is located in the outer spiral arm of the Milky Way, about 30, 000 light years from the center of the galaxy
Milky Way Galaxy
Rotates about its center It takes 200 million years for the
solar system to revolve around the galaxy
The Milky Way Gaalaxy
Types of Galaxy
Elliptical Galaxies
Vary in shape from nearly spherical to resembling a flat disk
Contain very little dust Have stars that are generally older
than those in other types
Elliptical Galaxy
Spiral Galaxies
Made up of thick mass of material and flattened arms that spiral around the center
Milky Way and Andromeda galaxy are spiral galaxies
Spiral Galaxy (Andromeda)
Irregular Galaxies
Have no definite shape Large and Small Magellanic Clouds
are some examples
Irregular Galaxy
Star Clusters
Smaller groups of stars within a galaxy
They are gravitationally bound There are two types of star clusters
in the Milky Way galaxy Most star clusters are far from the
solar system and appear as fuzzy patches in the night sky
The open cluster and the globular cluster
Open Cluster
Contains large, loosely organized groups of stars
Pleiades, one of its examples, can be seen in the constellation of Taurus in winter
Open Cluster (Pleiades)
Globular Cluster
Group of stars in spherical shape Many contain more than 100,000
stars Example is the cluster in the
constellation Hercules
Globular Cluster
Multiple Star System
Clusters that contain stars in much smaller groups
Binary stars are stars found in pairs Eclipsing binary is a binary star
system in which one star blocks out the light from its companion star
Binary Stars