lecture ch 06 [compatibility mode] ast 201

Chapter 6

The Solar Systemy

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 PlanetsTerrestrial and Jovian Planets

Interplanetary DebrisInterplanetary Debris

Units of Chapter 6, cont.

Spacecraft Exploration of the Solar System

Gravitational “Slingshots”g

How Did the Solar System Form?Th C t f A l M tThe Concept of Angular Momentum

6.1 An Inventory of the Solar System

Earl astronomers kne Moon stars Merc rEarly astronomers knew Moon, stars, Mercury, Venus, Mars, Jupiter, Saturn, comets, and meteorsmeteors

Now known: Solar system has 135 moons, one star nine planets (added Uranus Neptune andstar, nine planets (added Uranus, Neptune, and Pluto), asteroids, comets, and meteoroids

6.2 Planetary Properties

6.2 Planetary Properties

• Distance from Sun known by Kepler’s laws

• Orbital period can be observed

Radius known from angular size• Radius known from angular size

• Masses from Newton’s laws

• Rotation period from observations

• Density can be calculated knowing radius and• Density can be calculated knowing radius and mass

6.4 Terrestrial and Jovian Planets

Terrestrial planets:

Mercury, Venus, Earth, Mars

Jovian planets:

Jupiter, Saturn, Uranus,Jupiter, Saturn, Uranus, Neptune

Pluto is neitherPluto is neither

6.4 Terrestrial and Jovian PlanetsDifferences between the terrestrial planets:Differences between the terrestrial planets:

• Atmospheres and surface conditions are very di i ildissimilar

• Only Earth has oxygen in atmosphere and liquid water on surfacewater on surface

• Earth and Mars rotate at about the same rate; Venus and Mercury are much slower and Venus rotates in theand Mercury are much slower, and Venus rotates in the opposite direction

• Earth and Mars have moons; Mercury and VenusEarth and Mars have moons; Mercury and Venus don’t

• Earth and Mercury have magnetic fields; Venus and y g ;Mars don’t

6.6 Spacecraft Exploration of the Solar Systemy

Sojourner was deployed on Mars in 1997:

6.7 How Did the Solar System Form?N b l iNebular contraction:

Cloud of gas and dust contracts due to gravity; conservation of angular momentum means it spins faster and faster as it contracts

6.7 How Did the Solar System Form?

Condensation theory:yInterstellar dust grains

help cool cloud, and act as condensation nuclei

Summary of Chapter 6

• Solar system consists of Sun and everything orbiting it

• Asteroids are rocky, and most orbit between orbits of Mars and Jupiterp

• Comets are icy, and are believed to have formed early in the solar system’s lifeformed early in the solar system s life

• Major planets orbit Sun in same sense, and all but Venus rotate in that sense as wellbut Venus rotate in that sense as well

• Planetary orbits lie almost in the same plane

Summary of Chapter 6, cont.

• Four inner planets – terrestrial planets – are rocky, small, and densey

• Four outer planets – jovian planets – (omitting Pluto) are gaseous and largePluto) are gaseous and large

• Nebular theory of solar system formation: cloud of gas and dust gradually collapsed undercloud of gas and dust gradually collapsed under its own gravity, spinning faster as it shrank

C d ti th d t i t d• Condensation theory says dust grains acted as condensation nuclei, beginning formation of larger objectslarger objects