1. Earth Science Chapter 17 Sections 1-2
The Solar System
Earth Science
Chapter 17
Sections 1-2

2. Solar System
The sun and all things orbiting around it, including the eight major planets, their satellites, and all the smaller pieces such as asteroids, meteoroids, and comets.
Not to scale
Image taken from:

3. Formation of the Solar System
Formed around 4.6 billion years ago
Solar Nebula
Huge cloud of gas and dust that collapsed into a flattened disk 1
Disk
Sun formed at the center of the disk while other objects (planets, moons, etc.) formed from the whirling material of the disk 2
Solar System
Much of the material was cleared away. The Sun, planets, and other objects remained 3
Images taken from:

4. Planet Derived from a Greek word that means “wanderer”
A major object which orbits around a star
In our solar system, there are eight such objects which are traditionally called “planets”

5. Planet Classifications
Terrestrial Planets
(inner planets)
Mercury, Venus, Earth, Mars
closest to the sun
composed primarily of rock and metal
have deep atmospheres (except Mercury), solid surfaces, no rings, & few satellites
Gas Planets
(outer planets)
Jupiter, Saturn, Uranus, Neptune
composed primarily of hydrogen & helium
have deep atmospheres, rings, & many satellites

6. Other Planet Classifications
Three dwarf planets:
- Ceres
- Pluto
- Eris
Inner and Outer planets separated by Main Asteroid Belt
Beyond orbit of Neptune is the Kuiper Belt- small icy bodies

7. Orbit
The path of an object in space as it travels around another object
Planets orbit around the sun in an elliptical (flattened circle or oval) path; proposed by Johannes Kepler  Kepler’s 1st Law
Due to the gravitational attraction, a planet’s (or other object’s) speed increases as it approaches the sun
Planetary Motion
Not to scale
The Earth animation is not rotating in the correct direction;
it should be rotating from west to east
What do you think is the relationship between a planet’s orbit and a “year?”

8. Orbit Ellipse- a slightly flattened circle or oval
Perihelion- the point at which a planet is closest to the Sun
Aphelion- the point at which a planet is furthest from the Sun
Figure 17.6 page 410

9. Orbit
Orbital velocity- the speed at which a planet travels in its orbit
Planet moves fastest- perihelion
Planet moves slowest- aphelion
Greater gravitational attraction between objects that are closer

10. Mass vs. Weight Mass a measure of how much matter an object is made of
does not change, regardless of where something or someone is
Weight
the force of gravity on an object
equal to the mass of the body times the local acceleration of gravity
Why do you think the person’s weight is less on the moon?
The Earth animation is not rotating in the correct direction;
it should be rotating from west to east
Mass = 59 kg
Mass = 59 kg
Weight = 579 N
Weight = 96 N

11. Rotation vs. Revolution
the movement or path of the earth or a heavenly body turning on its axis
equivalent to one “day”
Earth rotates at a speed of around 1,670 km/hr or 1000 mi/hr
Revolution
the motion of one body around another, such as Earth orbiting around the sun
also known as an orbital period
equivalent to one “year”
Earth revolves at a speed of around 107,000 km/hr or 67,000 mi/hr
The Earth animation is not rotating in the correct direction;
it should be rotating from west to east
Sun
Tips for remembering:
rotation occurs in one day; day has three letters and rotation has three syllables
revolution occurs in one year; year has four letters and revolution has four syllables