Mars. Jovian. Jupiter. Saturn. Uranus. Neptune. Overal

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The Solar System
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The Suns Family - the Giants
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The Suns Family - the Dwarfs
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Planet Types

• Terrestrial
• Mercury
• Venus
• Earth
• Mars

• Jovian
• Jupiter
• Saturn
• Uranus
• Neptune

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Overall System Properties

• Orbits coplanar
• Orbit in same direction
• Most rotate in same direction
• Moons tend to orbit parent body in the same
  direction
• Lenticular laws
• Diameter
• Number of moons

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Orbital Inclinations
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Comparing the Planet Types

• Distance from Sun
• Diameter
• Mass
• Density
• Composition
• Rotation Rate

Close
Far
Small
Large
Large
Small
Small
Large
Solar
Rocky
Slow
Rapid
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Planetary Observations

• Mass
• Follow the orbit of a moon.
• Follow the trajectory of a spacecraft.
• Perturbations in the orbit of a nearby planet.

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Planetary Observations

• Radius
• Angular Diameter and Distance

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Angular Diameter and Distance
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Planetary Observations

• Radius
• Angular Diameter and Distance
• Stellar Occultations

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Stellar Occultations
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Rings of Uranus
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The Discovery of Uranus

• William Hershel 1781
• Perturbations in the orbit discovered
• Must be due to another planet
• Fg ? M/d2
• Mass from trends in the outer solar system
• Assumed about the mass of Uranus
• Distance from Bodes Law

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Bode-Titius Law
Mercury d Venus e Earth ? Mars
f Jupiter g Saturn h Uranus i
0.4 0.7 1.0 1.6 2.8 5.2 10.0 19.6
4 7 10 16 28 52 100 196
0 3 6 12 24 48 96 192
Asteroids
384 388 38.8
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Neptune Found

• Position predicted by John Couch Adams and Urbain
  Jean Joseph Le Verrier
• Observed by Johann Gottfried Galle and Heinrich
  Louis dArrest on Sept 23, 1846
• Two moons found quickly
• Mass 17.2 M?
• Distance 30 AU

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The search for Planet IX

• Soon became apparent that Neptune didnt solve
  all the problems
• New search conducted by Percival Lowell
• Looking for a small Jovian planet
• Mass 6.6 M?
• Magnitude 10
• Clyde Tombaugh succeeds in 1930
• Named Pluto
• Fainter than expected

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Pluto Found
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The Mass of Pluto

• Pre-discovery 6.6 M?

1968 0.91
1976 0.11
1978 0.0002
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More Planets?

• Reanalysis of Voyager 2 data suggests that all
  perturbations are accounted for
• In fact the hunt for Pluto need not have been
  conducted if more accurate data had been available

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The Kuiper Belt
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Planetary Observations

• Radius
• Angular Diameter and Distance
• Stellar Occultations
• Radar

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Radar
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Radius by Radar

• Send out very short pulse
• One nanosecond is typical
• Signal reflects off of different parts of the
  planet at different times
• Returned signal spread out in time

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Planetary Observations

• Rotational Period
• Radar

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Rotational Rate by Radar

• Send out signal of only one wavelength
• Signal is Doppler shifted by surface of a
  rotating planet
• Signal received spread out in wavelength

Blue Shift here
Red Shift here
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Rotation of Mercury
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Rotation of Venus

• Orbital Period224.7d
• Rotational period243d retrograde
• always presents the same face toward Earth when
  the two planets are at their closest approach.

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Radar Map of Mercury
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Comparing Twins
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Venus
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Other Radar Findings

• Jupiter
• No solid surface
• Saturn
• Nature of Rings

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Planetary Observations

• Rotational Period
• Radar
• Surface features

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Planetary Observations

• Rotational Period
• Radar
• Surface features
• Slant of spectral lines

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Spectrum of Saturn
Slit of Spectrograph
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Planetary Observations

• Rotational Period
• Radar
• Surface features
• Slant of spectral lines
• Light variations

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Asteroid Ida
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Planetary Observations

• Albedo
• Information required
• Sun-Planet distance
• Planet-Earth distance
• Brightness of Sun
• Brightness of Planet
• Basic Information on surface, atmosphere,
  clouds, ice caps

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Albedos

• Mercury 0.11
• Venus 0.65
• Earth 0.37
• Mars 0.15
• Jupiter 0.52
• Saturn 0.47
• Uranus 0.50
• Neptune 0.5
• Pluto 0.6

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End of Section