A Survey of the Solar System
Please take your assigned transmitter.
If your name is not yet on the transmitter list, take
any transmitter with no. above 225.
Class web site:
http://www.phy.ohiou.edu/~mboett/PSC100D/winter09/PSC100D_winter09.html
The Relative Sizes of the Planets
Take a guess: In a model where the Earth
has the size of a pingpong ball, what would
be the diameter of the sun?
1.
2.
3.
4.
5.
10 cm (tennis ball)
30 cm (basket ball)
1 m (3 feet)
4 m (height of the lecture hall)
15 m (width of the lecture hall)
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).
Sun: ~ 4 m (109 times Earth’s diameter).
Mercury: ~ 1.1 cm
Venus, Earth: ~ 3.7 cm (pingpong ball)
Mars: ~ 2 cm
Jupiter: ~ 41 cm
Saturn: ~ 35 cm
Uranus: ~ 15 cm
Neptune: ~ 14 cm
Pluto: ~ 7 mm (orange seed)
The Orbits of the Planets
In our pingpong-ball-Earth model, how far
away would the sun be?
1.
2.
3.
4.
5.
15 m (across this lecture hall)
50 m (across this building)
500 m (Hocking River)
20 km (Nelsonville)
120 km (Columbus)
Planetary Orbits
Mercury
Venus
Earth
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)
(Distances and times reproduced to scale)
Orbits generally
inclined by no
more than 3.4o
Exceptions:
Mercury (7o)
Pluto (17.2o)
Planetary Orbits and Rotation
Retrograde rotation
Tipped over by
more than 900
Mercury and Pluto: Unusually highly inclined orbits
Distance Scales
In our pingpong-ball-Earth model, how far
away would a Centauri (the closest star
other than our sun) be?
1.
2.
3.
4.
5.
20 km (Nelsonville)
120 km (Columbus)
720 km (New York City)
6,500 km (Paris, France)
120,000 km (1/3 the way to the moon)
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
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.
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
Space Debris
In addition to planets, small bodies orbit the sun:
Asteroids, comets, meteoroids
Asteroid
Eros,
imaged by
the NEAR
spacecraft
The Asteroid Belt
Most asteroids
orbit the sun in a
wide zone
between the
orbits of Mars
and Jupiter.
(Distances and times reproduced to scale)
Comets
Icy nucleus, which evaporates
and gets blown into space by
solar wind pressure.
Mostly objects in highly elliptical orbits,
occasionally coming close to the sun.
What is (approximately) the size
of the solar system?
1.
2.
3.
4.
5.
384,000 km
1 AU
100 AU
1 light year
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 (mm – 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.