1. Star Groups
Mr. Silva
Ag Earth Science

2. Stars
The visible stars you see at night are only some of
the stars in our galaxy.
Most stars seem to be single stars, but in actuality
they are mostly doubles and triples.
 1/3 are doubles
 ¼ are singles

3. Constellations
Constellations are patterns of starts.
They may look like they are close together but really
they are extremely far apart.
We recognize 88 different constellations.
Named after gods, heroes or fierce animals.

4. Galaxies
The major components of the universe are
galaxies.
They are large groups of stars bound together by
gravitational attraction.
Made up of millions of stars, dust clouds and
gases.
Estimated 50 billion and 1 trillion galaxies in the
universe.
We live in the Milky Way Galaxies.

5. Types of Galaxies
Spiral Galaxy: has a nucleus or bright center
with flattened arms that spiral around the nucleus.

6. Types of Galaxies
Elliptical Galaxy: They are very bright centers and
do not have spiral arms. Have no young stars and
contain very little dust and gas.

7. Types of Galaxies
Irregular Galaxy: has no particular shape. They
are very small and faint. Very little gravitational
pull.

8. The Milky Way
Our galaxy
Spiral galaxy
Has a diameter of 100,000 light years
Our sun is about 30,000 light years from the center.
Revolves at a speed of 250km/s.
Takes 200 million years to make one revolution.

9. Formation of the Universe
The big bang theory- matter was all concentrated in
an extremely small volume
Occurred 12-15 billion years ago.
Galaxies are continuing to move outward.

10. Formation of the Universe
The big bang theory- matter was all concentrated in
an extremely small volume
Occurred 12-15 billion years ago.
Galaxies are continuing to move outward.