3. Interplanetary Debris

! Asteroids,

! Comets,

! Kuiper Belt and Oort Cloud

Chapter 6 Part A1. The Solar System

! Inventory of the Solar

System

! Planetary Orbits, Spins

Masses of Planets

! Densities of the Planets

2. Classes of Planets

! Terrestrial,

! Jovian,

! Major Moons

• Sun

• Planets

Terrestrial & Jovian

• Moons

• Over 162

Inventory of the Solar System

• Asteroids

–Small, rocky, minor planets. Most are located in the asteroid belt.

• Comets

–Small, icy bodies--Dirty Snowballs.

• Interplanetary gas and dust

• Solar Winds

There are eight "classical" planets

(Mercury thru Neptune, including Earth but not Pluto).

outer planets: Jupiter, Saturn,

Uranus, Neptune.

inner planets:

Mercury,

Venus, Earth

and Mars.

Planets, by the new IAU definition, must be in orbit around the sun, be

nearly spherical, and must have cleared the neighborhood around their

orbits.

Dwarf Planets

Planets orbit essentially in the same plane (Ecliptic)

Largest Orbital inclination are Mercury (7 degrees) and

Pluto(17 degrees)

Orbits

Outer PlanetsInner Planets

Orbits counter-clockwise

Orbits nearly circular

5.2 9.554 19.14 30.066 AU

.382 .723 1 1.524 AU

Astronomical Unit (AU)= Earth-Sun Distance or 150 million km! 1.5 108

km

Obliquity Rot Per (hrs

Jupiter 3.12° 9.925

Saturn 26.73° 10.656

Uranus 97.86° 17.24

Neptune 29.56° 16.11

Pluto 119.6 153.29

Inner Planets Outer Planets

Sec 1

"The spin axes of most planets and moons are perpendicular to

the orbital plane (Exceptions: Venus,Uranus and Pluto).

Obliquity Rot Per (hrs)

Mercury 0.1° 1407.5

Venus 177.4° 5832.5

Earth 23.45° 23.9

Mars 25.19° 24.6

Sun ~ 300,000 times mass of Earth

Mass of Planets (units of Earth Masses}

Sec 1

Solar System MassSun 99.80%

Jupiter 0.10%

Comets 0.05%

Other 8 planets 0.04%

Total of Sun + Planets +

Comets = 99.99%

Size of the planets

Density• Density measures the “type” of matter.

Density = mass/volume (g/cm3)

• For a planet:

– From the diameter you can calculate volume.

– From the mass you can calculate the average density.

Density of water = 1.0 g/cm3 ;

Density of silicate rock = 3.0 g/cm3

Density of iron = 7.8 g/cm3

Sec 1

A denser object occupies less volume thanan equal mass of some less densesubstance

Terrestrial !5

Jovian !1 to 2

Density of

PlanetsTwo distinct groups of planets classifying by

composition(Density).

Dwarf

Jovian Planets:Jupiter,

Saturn, Uranus, Neptune

Sec 2

Jovian or gas planets:

!composed primarily of

hydrogen and helium

! have low densities,

! rapid rotation,

!deep atmospheres,

! rings and lots of satellites

Terrestrial Planets:

Mercury Venus Earth Mars

! small objects close to Sun

!Rotation rate: Earth and

Mars ~ 24 hrs, Mercury ~ 2

months, Venus ~ 8 months

!Few moons: Earth - 1, Mars -

2 Mercury and Venus - 0

! solid surfaces that record their

history in craters, mountains, and

volcanoes.

!High density: mostly rock and metal

composition

!Atmospheres: near vacuum to dense

hot gas

Major Moons

Saturn has one

large satellite Titan

with its dense and

organic-rich

atmosphere

together with

numerous much

smaller satellites.

Jupiter's four

Galilean satellites

are each roughly

similar in size.

They include

volcanic Io and

Europa with its

believed

subsurface ocean.

• Relatively small, rocky objects that revolve around the Sun.

– Much smaller than planets.

– Largest known: Ceres

• 940 km diameter (480 miles)

• 1/10,000 mass of Earth

• Most move in orbits between Mars and Jupiter.

• remnants of objects that didn’t form a planets.

Asteroid Belt

“Dirty Snow Balls”

Composed largely of ices--- water ice, ammonia ice, methane ice---

mixed with dust Inhabit two distinct regions of space:

Kuiper Belt and Oort cloud.

Comets Kuiper Belt

Kuiper belt, an icy belt of comet-like bodies extending beyond Neptune's

orbit (30-100 AU ). Kuiper belt Comets orbit in same direction as planets

and in same general plane.

Oort cloud Extends to 1/3 of way to nearest star. Orbit at

any inclination and direction.

End of Chapter 6a

Go to Chapter 6b