1. A Survey of the Solar System Class web site: http://www.phy.ohiou.edu/~mboett/PSC100D/winter09/PSC100D_winter09.html Please take your assigned transmitter. If your name is not yet on the transmitter list, take any transmitter with no. above 225.

2. The Relative Sizes of the Planets 1.10 cm (tennis ball) 2.30 cm (basket ball) 3.1 m (3 feet) 4.4 m (height of the lecture hall) 5.15 m (width of the lecture hall) Take a guess: In a model where the Earth has the size of a pingpong ball, what would be the diameter of the sun?

3. Relative Sizes of the Planets Assume, we reduce all bodies in the solar system so that the Earth has diameter 3.7 cm (pingpong ball). Mercury: ~ 1.1 cm Sun: ~ 4 m (109 times Earth’s diameter). Jupiter: ~ 41 cm Saturn: ~ 35 cm Uranus: ~ 15 cm Pluto: ~ 7 mm (orange seed) Venus, Earth: ~ 3.7 cm (pingpong ball) Mars: ~ 2 cm Neptune: ~ 14 cm

4. The Orbits of the Planets In our pingpong-ball-Earth model, how far away would the sun be? 1.15 m (across this lecture hall) 2.50 m (across this building) 3.500 m (Hocking River) 4.20 km (Nelsonville) 5.120 km (Columbus)

5. Planetary Orbits Pluto Neptune Uranus Saturn Jupiter Mars Earth Venus Mercury All planets revolve in almost circular (elliptical) orbits around the sun, in approx. the same plane (ecliptic). Sense of revolution: counter-clockwise Sense of rotation: counter-clockwise (with exception of Venus, Uranus, and Pluto) Orbits generally inclined by no more than 3.4 o Exceptions: Mercury (7 o ) Pluto (17.2 o ) (Distances and times reproduced to scale)

6. Retrograde rotationTipped over by more than 90 0 Mercury and Pluto: Unusually highly inclined orbits Planetary Orbits and Rotation

7. In our pingpong-ball-Earth model, how far away would a Centauri (the closest star other than our sun) be? 1.20 km (Nelsonville) 2.120 km (Columbus) 3.720 km (New York City) 4.6,500 km (Paris, France) 5.120,000 km (1/3 the way to the moon) Distance Scales

8. Two Kinds of Planets Planets of our solar system can be divided into two very different kinds: Terrestrial (earthlike) planets: Mercury, Venus, Earth, Mars Jovian (Jupiter-like) planets: Jupiter, Saturn, Uranus, Neptune

9. Terrestrial Planets Four inner planets of the solar system Relatively small in size and mass (Earth is the largest and most massive) Rocky surface Surface of Venus can not be seen directly from Earth because of its dense cloud cover.

10. The Jovian Planets Much larger in mass and size than terrestrial planets Much lower average density All have rings (not only Saturn!) Mostly gas; no solid surface

11. Space Debris In addition to planets, small bodies orbit the sun: Asteroids, comets, meteoroids Asteroid Eros, imaged by the NEAR spacecraftNEAR

12. The Asteroid Belt Pluto Neptune Uranus Saturn Jupiter Mars (Distances and times reproduced to scale) Most asteroids orbit the sun in a wide zone between the orbits of Mars and Jupiter.

13. Comets Mostly objects in highly elliptical orbits, occasionally coming close to the sun. Icy nucleus, which evaporates and gets blown into space by solar wind pressure.

14. What is (approximately) the size of the solar system? 1.384,000 km 2.1 AU 3.100 AU 4.1 light year 5.75,000 light years Remember: 1 AU = distance Sun – Earth = 150 million km

15. The Outer Regions of our Solar System Oort Cloud

16. What are shooting stars? 1.Stars that are shooting out material in large eruptions. 2.Stars falling from the sky. 3.Small solar-system bodies colliding with the Earth. 4.Comets colliding with the Earth. 5.Stars armed with guns.

17. Meteoroids Small (  m – mm sized) dust grains throughout the solar system If they collide with Earth, they evaporate in the atmosphere. Visible as streaks of light (“shooting stars”): meteors.