1. Please write down all the underlined items. Abbreviate to save time.
The Solar System
Please write down all the underlined items. Abbreviate to save time.

2. What is Astronomy? 1. Astronomy is the study of the universe.
This includes planets, stars, galaxies, black holes, moons, meteors, comets, asteroids and all of the matter that exists in space.
2. Astronomers are people who observe & study space.

3. Modern Calendar
Our modern calendar is based on the observations of bodies in our solar system.
2. A year is the time it takes for the Earth to orbit the sun; year = revolution.
3. A month is the time it takes for the moon to orbit the Earth.
4. A day is the time it takes for the Earth to rotate once on its axis; day = rotation.

4. The Size and Scale of our Universe
It is important to consider scale when we think about the universe.
Stars appear to be very small when viewed from Earth, but they are actually very large, some, like our sun, are bigger than Earth.

5. The Scale of our Solar System
Earth

6. Scale of the Universe
SUN
Mercury

7. Our Galaxy and Scale Our Milky Way galaxy is huge.
Let's now pretend that our galaxy is a kid's sandbox, and our sun is a grain of sand in a sandbox.
The Earth is a dust speck near the grain of sand, too small to be seen without a microscope.
If our sun were a grain of sand in this sandbox representing the Milky Way galaxy, the sandbox would be somewhat oval and yet flat, and would be about 20 feet in diameter.
The sand would be about 12 inches thick in the center, and thinner towards the edges.

8. THE MILKY WAY GALAXY: our
Each swirling object you see is a galaxy in our universe.
1. We can estimate that there are about 100 billion stars in our galaxy.
2. Andromeda is the nearest major galaxy to our own Milky Way Galaxy.
3. Most scientists believe that Andromeda is about 2 million light years away from the Milky Way.

9. Milky Way Galaxy: home to our solar system

10. Distance in Space
Distance in space—mainly distance outside of our solar system—is measured in light years.
Example: distance to another star; which is a very, very, large distance
A light year is the distance light travels in a year, 5.88 trillion miles. IT IS NOT TIME!!!
3. Light travels at 186,000 miles/sec or 300,000 km/s.
4. If it takes the light from a star 15 years to reach you, then how far away is the star?

11. Distance from the Sun to Earth = An Astronomical Unit
The distance from the Sun to the Earth is 93 million miles.
93 million miles = 1 astronomical unit
1 astronomical unit = (150 million kilometers)
this is the unit of measurement for distances b/w planets in our solar system

12. Astronomical Unit (AU) for the planets
Average Distance from the Sun (measured in AU)
Mercury
0.39
Venus
0.723
Earth
1.0
Mars
1.524
Jupiter
5.203
Saturn
9.539
Uranus
19.18
Neptune
30.06

13. The Sun: The Center of Our Solar System
Wider than 100 Earths
10,000 °F on surface & 27,000,000 °F in its core
less bright & massive than the very largest stars

14. Different Views of The Sun
3-D Image of the sun
Normal Telescopic Image of the sun
UV Image of the sun

15. Distances of the Inner Planets from the Sun in Astronomical Units (150 million km = 1 AU)

16. The Inner Planets: the terrestrial planets; all are dense & rocky
Mercury
Venus
Earth
Mars
They are solids & close to the sun because the materials that make them can be a solid at high temperatures.

17. The Outer Planets: The Gas Giants or Jovian Planets
Jupiter, Saturn, Uranus, & Neptune
All are made of gas. They are not solids like the inner planets.
They get denser with increasing depth.
All have rings. Some are barely visible unlike Saturn’s rings.
Since their masses are so much larger, they have more moons than the inner planets.
Which planet should have the largest number of moons?

18. Distances of the Outer Planets from the Sun in Astronomical Units (150 million km = 1 AU)
Jupiter
5.203 AU
Saturn
9.539 AU
Uranus
19.18 AU
Neptune
30.06 AU
Pluto
39 AU