A Survey of the Solar System

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A Survey of the Solar System
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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/P
SC100D/winter09/PSC100D_winter09.html
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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?

• 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)

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Relative Sizes of the Planets
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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 Earths 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)
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The Orbits of the PlanetsIn our
pingpong-ball-Earth model, how far away would the
sun be?

• 15 m (across this lecture hall)
• 50 m (across this building)
• 500 m (Hocking River)
• 20 km (Nelsonville)
• 120 km (Columbus)

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Planetary Orbits
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All planets revolve in almost circular
(elliptical) orbits around the sun, in approx.
the same plane (ecliptic).
Orbits generally inclined by no more than 3.4o
Mercury
Venus
Exceptions Mercury (7o) Pluto (17.2o)
Mars
Sense of revolution counter-clockwise
Earth
Jupiter
Sense of rotation counter-clockwise (with
exception of Venus, Uranus, and Pluto)
Pluto
Uranus
Saturn
Neptune
(Distances and times reproduced to scale)
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Planetary Orbits and Rotation
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Retrograde rotation
Tipped over by more than 900
Mercury and Pluto Unusually highly inclined
orbits
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In our pingpong-ball-Earth model, how far away
would a Centauri (the closest star other than our
sun) be?
Distance Scales

• 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)

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Two Kinds of Planets
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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
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Terrestrial Planets
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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.
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The Jovian Planets
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Much larger in mass and size than terrestrial
planets
Much lower average density
All have rings (not only Saturn!)
Mostly gas no solid surface
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Space Debris
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In addition to planets, small bodies orbit the
sun
Asteroids, comets, meteoroids
Asteroid Eros, imaged by the NEAR spacecraft
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The Asteroid Belt
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Most asteroids orbit the sun in a wide zone
between the orbits of Mars and Jupiter.
Mars
Jupiter
Pluto
Uranus
Saturn
Neptune
(Distances and times reproduced to scale)
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Comets
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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.
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What is (approximately) the size of the solar
system?

• 384,000 km
• 1 AU
• 100 AU
• 1 light year
• 75,000 light years

Remember 1 AU distance Sun Earth 150
million km
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The Outer Regions of our Solar System
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Oort Cloud
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What are shooting stars?

• Stars that are shooting out material in large
  eruptions.
• Stars falling from the sky.
• Small solar-system bodies colliding with the
  Earth.
• Comets colliding with the Earth.
• Stars armed with guns.

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Meteoroids
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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.