Studying the Solar System

• Our goals for learning• What does the solar system look like?• What can we learn by comparing the planets to

one another?• What are the major features of the Sun and

planets?

What does the solar system look like?1. What is in it?

•All large bodies in the solar system orbit in the same direction and in nearly the same plane

• Eight major planets with nearly circular orbits

• Pluto (dwarf planet) is smaller than the major planets and has a more elliptical orbit

Swarms of Smaller Bodies• Asteroids • Kuiper Belt

Objects• Oort Cloud• Comets

(short period, long period)

History of Planet Count

8Re-classification of Pluto, Eris & Ceres as “Dwarf planets”, others to follow as debate continues

2006

9?Discovery of several large KBOs, especially Eris which is larger than Pluto.

2000-20059?Discovery of 1992 QB1 and other Kuiper Belt Objects1992-19999?Discovery of Charon19789Discovery of Pluto19308Re-classification of Ceres and other small bodies1851

13+Discovery of Neptune184612Discovery of Astrea184511Discovery of Ceres, Palls & Vesta1801-18077Discovery of Uranus17816Heliocentric System, (Copernicus)15507Geocentric universe: Sun, Moon & 5 planetsAntiquity

Planet CountClassificaction/EventYear

What Counts as a Planet?The IAU definition of a planet (2006):• is in orbit around the Sun, • has sufficient mass so that it is nearly round• has "cleared the neighborhood" around its orbit.

What can we learn by comparing the planets to one another?

At first glance the worlds of the solar system all appear to be unique

Comparative Planetology

• Comparing the planets reveals common patterns. Those patterns provide insights that help us understand Earth

• Stay focused on processes common to multiple worlds instead of individual facts specific to a particular world.

• We can learn more about a world like our Earth by studying in context with other worlds in the solar system.

What are the major features of the Solar System?

Density and Composition

Density = = mass _ volume

• Measure a planet’s volume• Measure a planet’s spin => calculate mass

• Result is a world’s bulk density.

g/cm3

Density and Composition

• Common materials• Metals (mostly Iron) 7.9 g/cm3

• Rock (mostly Basalt) 3.3 g/cm3

• Carbon & hydrogen ices 0.4-1.5 g/cm3

(volatiles)• H and He gases <<0.01 g/cm3

Density and Composition

• Earth 5.5 g/cm3 composition- iron, rock

• Saturn 0.7 g/cm3 composition- some rock, volatiles and lots H&He

• Callisto 1.9 g/cm3 Titan 2 g/cm3 composition -rock and ice

Thought Question

Planet Mars has a bulk density of 3.9 g/cmg/cm33 What materials is it made of ?

A) Metal and Rock B) Rock and volatilesC) Rock and H&HeD) Volatiles and H & He

What have we learned?• What does the solar system look like?

– Planets orbit Sun in the same direction and in nearly the same plane.

• What can we learn by comparing the planets to one another?– Comparative planetology looks for patterns

among the planets. – Those patterns give us insight into the general

processes that govern planets– Studying other worlds in this way tells us

about our own Earth

What have we learned?• How can we tell what planets are made of?

– The bulk density of the planets reflect the type of materials the planets are composed of.

– There are 4 main common types of material

– Most planets are made of a mixture of these materials that are not necessarily represented on the surface.

• Over 99.9% of solar system’s mass• Made mostly of H/He gas (plasma)

Sun

What are the major features of the Solar System?

Three Main Types of Large Bodies• Terrestrial planets

(rocky worlds)• Jovian planets • (gas giant worlds)

• Ice worlds (mostly moons and dwarf planets)

Terrestrials vs Jovians• The terrestrial (or rocky) worlds are the 4 inner

planets plus our Moon– They have a solid rock surface with an iron

core and a weak to no atmosphere or magnetic field.

• There are 4 jovian (or gas giant) planets– These planets have NO solid surfaces – just gas

and clouds that get denser as you move to their center.

– They are mostly atmosphere around rocky cores and have a strong magnetic field

gas giant worlds are far from the Sun

Rockyworlds are

close to the Sun.

Jupiter – largest gas giant world

Earth – largest rocky world

gas giant worlds are much larger than rocky worlds

Rocky worlds have no rings and no, or few, moons.

Gas Giant worlds have rings and many moons.

Ice Worlds• Enough self-gravity to be spherical.• Metal/rock core, ice mantle and crust.• Some geological activity• Two main locations:

– Larger Icy moons orbiting gas giant planets– Largest objects in Kuiper belt in the outermost

solar system (Pluto, Sedna, Quoaor and others)

Swarms of Smaller Bodies• Many rocky asteroids

and icy comets populate the solar system

• Solar system debris can be found everywhere, but close to the sun it is rocky and far from the sun, icy.

What have we learned?• What are the major features of the Solar

System– Motions of large bodies: All in same direction

and plane– Two main planet types: Terrestrial and jovian– Minor type: ice worlds– Swarms of small bodies: Asteroids and

comets

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Which planets DO have rings?

A.Saturn onlyB.Saturn and Uranus onlyC.Saturn, Uranus and Neptune onlyD.Saturn, Jupiter, Uranus and Neptune onlyE.All the planets have rings.

© 2014 Pearson Education, Inc.

At what location(s) within the solar system would one find comets?

A.the Oort cloud and the Kuiper belt

B.the asteroid belt onlyC.the Kuiper belt and the

asteroid beltD.the Kuiper belt onlyE.the Oort cloud only