1. Welcome to the Milky Way Galaxy

2. Galaxies
A galaxy is a “system of millions or billions of stars, together with dust and gas, held together by gravitational attraction.”
There are 3 types of galaxies: Elliptical, Spiral, and Irregular
Elliptical galaxies are elongated spheres
Spiral galaxies have a spherical shape in the center with arms spiraling out
Both Elliptical and Spiral galaxies have further classifications
Irregular galaxies have no regular shape to them
According to astronomers, their best estimate predicts there are at least 100 billion galaxies in the observable universe.

3. Elliptical Galaxy (NGC-1316; 62 million light years away)

4. Spiral Galaxy (M83, otherwise known as the Southern Pinwheel Galaxy; 15 million light years away)

5. Irregular Galaxy (NGC-1569; 8,000 light years across; 11 million light years away; considered a very close and young galaxy)

6. Milky Way Galaxy
This is an artist’s conception of what the Milky Way Galaxy looks like. The artist based the picture on different photos taken by astronomers.
Why don’t we have any real pictures of the Milky Way Galaxy?
Where are we located in this picture?

7. Milky Way Galaxy
We cannot photograph the Milky Way because it is so large, and we are in it.
The Milky Way Galaxy is estimated to be 100,000 light years across. There are approximately 300 billion stars in our galaxy.
That means that it would take light (the fastest speed we know) 100,000 years to travel across the Galaxy.
Our Sun, and entire Solar System is located within the Orion Arm of the Galaxy. We are a mere dot in our Galaxy.

8. Sun Centered Model of the Solar System
Until the year 1543, it was believed that the Earth was the center of our system.
Copernicus and Galileo studied Astronomy and both contributed to what we now know of our Solar System.
The Sun is the center of our Solar System. The moon orbits the Earth and the Earth and 7 other planets orbit the Sun.
Pluto was a planet for a long time, but is now no longer considered one.
Pluto is no longer considered a planet because of its size, location in space, and tilt of orbit in comparison with the other planets in our Solar System.

9. Inner Planets
Mercury, Venus, Earth, and Mars are considered the ‘Inner Planets’
Also known as “Terrestrial Planets,” which is misleading
Smaller
Either no or few moons
Made of mostly heavy metals, lots of iron and nickel
Solid Surfaces
No rings
Spin slowly compared to outer planets
Orbit the Sun quickly

10. Mercury

11. Venus

12. Earth

13. Mars
"Mars Hubble" by NASA and The Hubble Heritage Team (STScI/AURA) - (direct link) Licensed under Public Domain via Wikimedia Commons -

14. Surface of Mars

15. Outer Planets Jupiter, Saturn, Uranus, and Neptune
Also known as the “Gas Giants”
Largest planets
Many moons
Made primarily of gas
All have rings
Spin quickly
Orbit sun slowly

16. Jupiter
"Jupiter gany" by NASA/JPL - ftp://nssdcftp.gsfc.nasa.gov/miscellaneous/planetary/voyager/jupiter/vg1_p20945.tiff. Licensed under Public Domain via Wikimedia Commons -

17. Saturn
"Saturn false color Voyager-1" by NASA - Licensed under Public Domain via Wikimedia Commons -

18. Uranus
"Uranus" by NASA/JPL - Licensed under Public Domain via Wikimedia Commons -

19. Neptune
"Neptune" by NASA/JPL - Licensed under Public Domain via Wikimedia Commons -

20. Asteroid Belt
Separating the inner and outer planets is an asteroid belt.