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.

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?

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

The Orbits of the PlanetsIn 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)

Planetary Orbits

Plu

toN

eptu

neUra

nus

Saturn

Jupi

terM

ars

Earth

VenusMercury

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 3.4o

Exceptions:

Mercury (7o)

Pluto (17.2o)

(Distances and times reproduced to scale)

Retrograde rotation Tipped over by more than 900

Mercury and Pluto: Unusually highly inclined orbits

Planetary Orbits and Rotation

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

Two Kinds of PlanetsPlanets 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

Terrestrial PlanetsFour 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.

The Jovian PlanetsMuch larger in mass

and size than terrestrial planets

Much lower average density

All have rings (not only Saturn!)

Mostly gas; no solid surface

Space DebrisIn addition to planets, small bodies orbit the sun:

Asteroids, comets, meteoroids

Asteroid Eros,

imaged by the NEAR spacecraft

The Asteroid Belt

Plu

toN

eptu

neUra

nus

Saturn

Jupi

terM

ars

(Distances and times reproduced to scale)

Most asteroids orbit the sun in a

wide zone between the

orbits of Mars and Jupiter.

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.

What is (approximately) the size of the solar system?1. 384,000 km2. 1 AU3. 100 AU4. 1 light year5. 75,000 light years

Remember:

1 AU = distance Sun – Earth = 150 million km

The Outer Regions of our Solar System

Oort Cloud

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.

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.