1. Chapter 6
The Solar System
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2. Units of Chapter 6
An Inventory of the Solar System
Planetary Properties
Computing Planetary Properties
The Overall Layout of the Solar System
Terrestrial and Jovian Planets
Interplanetary Debris

3. Units of Chapter 6, cont.
Spacecraft Exploration of the Solar System
Gravitational “Slingshots”
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How Did the Solar System Form?
The C
Th Concept of Angular Momentum
t fA l M t

4. 6.1 An Inventory of the Solar System
Early
Earl astronomers kne Moon, stars, Merc r
knew Moon stars Mercury,
Venus, Mars, Jupiter, Saturn, comets, and
meteors
Now known: Solar system has 135 moons, one
star,
star nine planets (added Uranus Neptune and
Uranus, Neptune,
Pluto), asteroids, comets, and meteoroids

5. 6.2 Planetary Properties

6. 6.2 Planetary Properties
• Distance from Sun known by Kepler’s laws
• Orbital period can be observed
• Radius known from angular size
• Masses from Newton’s laws
• Rotation period from observations
• Density can be calculated knowing radius and
mass

7. 6.4 Terrestrial and Jovian Planets
Terrestrial planets:
Mercury, Venus, Earth,
Mars
Jovian planets:
Jupiter, Saturn, Uranus,
Neptune
Pluto is neither

8. 6.4 Terrestrial and Jovian Planets
Differences between the terrestrial planets:
• Atmospheres and surface conditions are very
dissimilar
di i il
• Only Earth has oxygen in atmosphere and liquid
water on surface
• Earth and Mars rotate at about the same rate; Venus
and Mercury are much slower and Venus rotates in the
slower,
opposite direction
• Earth and Mars have moons; Mercury and Venus
don’t
• Earth and Mercury have magnetic fields; Venus and
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Mars don’t

9. 6.6 Spacecraft Exploration of the
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Solar System
Sojourner was deployed on Mars in 1997:

10. 6.7 How Did the Solar System Form?
Nebular
N b l contraction:
i
Cloud of gas and dust contracts due to gravity;
conservation of angular momentum means it spins
faster and faster as it contracts

11. 6.7 How Did the Solar System Form?
Condensation theory:
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Interstellar dust grains
help cool cloud, and act as
condensation nuclei

12. Summary of Chapter 6
• Solar system consists of Sun and everything
orbiting it
• Asteroids are rocky, and most orbit between
orbits of Mars and Jupiter
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• Comets are icy, and are believed to have
formed early in the solar system s life
system’s
• Major planets orbit Sun in same sense, and all
but Venus rotate in that sense as well
• Planetary orbits lie almost in the same plane

13. Summary of Chapter 6, cont.
• Four inner planets – terrestrial planets – are
rocky, small, and dense
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• Four outer planets – jovian planets – (omitting
Pluto) are gaseous and large
• Nebular theory of solar system formation:
cloud of gas and dust gradually collapsed under
its own gravity, spinning faster as it shrank
•C d
Condensation theory says dust grains acted as
ti th d t i t d
condensation nuclei, beginning formation of
larger objects