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The Solar SystemThe Solar System

Essential QuestionsEssential Questions

�� What are planets?What are planets?

�� What are the types of planets?What are the types of planets?

�� How do we determine how far apart the How do we determine how far apart the

planets are?planets are?

�� What is the difference between a meteor What is the difference between a meteor

and a meteorite?and a meteorite?

�� What is an asteroid?What is an asteroid?

�� What are comets?What are comets?

�� What are the types of comets?What are the types of comets?

What are Planets?What are Planets?

IAU definition of PlanetIAU definition of Planet

� Former definition

• A non-luminous celestial body larger than an asteroid or comet, illuminated by light from a star, such as the sun, around which it revolves.

� A planet is a celestial body that • (a) is in orbit around the Sun,

• (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and

• (c) has cleared the neighbourhood around its orbit.

What are the Types of Planets?What are the Types of Planets?

Types of PlanetsTypes of Planets

�� Terrestrial PlanetsTerrestrial Planets

�� Jovian PlanetsJovian Planets

�� Dwarf PlanetsDwarf Planets

Terrestrial PlanetsTerrestrial Planets

�� Smaller size and massSmaller size and mass

�� Higher densityHigher density

�� Made mostly of rock and metalMade mostly of rock and metal

�� Solid surfaceSolid surface

�� Few, if any, moonsFew, if any, moons

�� No ringsNo rings

�� Closer to the Sun and each otherCloser to the Sun and each other

�� Warmer surfacesWarmer surfaces

�� Mercury, Venus, Earth, MarsMercury, Venus, Earth, Mars

VideoVideo

�� ““A Spin Around the Solar System: A Spin Around the Solar System:

Our Rocky Neighbors: The Inner Our Rocky Neighbors: The Inner

PlanetsPlanets””

MercuryMercury

�� Diameter = 4872 kmDiameter = 4872 km

�� Distance to the Sun =57.9 million Distance to the Sun =57.9 million

km km

VenusVenus

�� Diameter =12 104kmDiameter =12 104km

�� Distance to the Sun = 108.2 million Distance to the Sun = 108.2 million

kmkm

EarthEarth

�� Diameter =12 756 kmDiameter =12 756 km

�� Distance to the Sun =149.6 million Distance to the Sun =149.6 million kmkm

�� Orbit period = 356.26 daysOrbit period = 356.26 days

�� Orbit speed = 108 000 km/sOrbit speed = 108 000 km/s

�� Axis rotation = 23.93 hoursAxis rotation = 23.93 hours

�� Axis tilt = 23.5Axis tilt = 23.5oo

�� Acceleration = 9.81 m/sAcceleration = 9.81 m/s22

MarsMars

�� Diameter =6 780 kmDiameter =6 780 km

�� Distance to the Sun =227.9 million Distance to the Sun =227.9 million

kmkm

Jovian PlanetsJovian Planets

�� Larger size and massLarger size and mass

�� Lower densityLower density

�� Mostly made of hydrogen, helium, and Mostly made of hydrogen, helium, and hydrogen compoundshydrogen compounds

�� No solid surfaceNo solid surface

�� Many moonsMany moons

�� RingsRings

�� Farther from the sun and each otherFarther from the sun and each other

�� Cool temperatures at cloud topsCool temperatures at cloud tops

�� Jupiter, Saturn, Uranus, NeptuneJupiter, Saturn, Uranus, Neptune

VideoVideo

�� ““A Spin Around the Solar System: A Spin Around the Solar System:

The Outer Planets the Gas GiantsThe Outer Planets the Gas Giants””

JupiterJupiter

�� Diameter =142 984 kmDiameter =142 984 km

�� Distance to the Sun =778.4 million Distance to the Sun =778.4 million

kmkm

SaturnSaturn

�� Diameter =120 536 kmDiameter =120 536 km

�� Distance to the Sun =1.4 billion kmDistance to the Sun =1.4 billion km

UranusUranus

�� Diameter =51 118 kmDiameter =51 118 km

�� Distance to the Sun =2.4 billion kmDistance to the Sun =2.4 billion km

NeptuneNeptune

�� Diameter =49 532 kmDiameter =49 532 km

�� Distance to the Sun = 4.5 billion kmDistance to the Sun = 4.5 billion km

Dwarf PlanetsDwarf Planets

�� Pluto, Ceres, ErisPluto, Ceres, Eris

IAU definition of a Dwarf PlanetIAU definition of a Dwarf Planet

� A "dwarf planet" is a celestial body that

• (a) is in orbit around the Sun,

• (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape2,

• (c) has not cleared the neighbourhood around its orbit, and

• (d) is not a satellite.

VideoVideo

�� ““A Spin Around the Solar System: A Spin Around the Solar System:

The Small Pieces: Asteroids, Comets, The Small Pieces: Asteroids, Comets,

and and PlutoPluto””

CeresCeres

�� Diameter = 974.6kmDiameter = 974.6km

�� Distance to the Sun = Distance to the Sun =

413 832 587.5 km413 832 587.5 km

PlutoPluto

�� Diameter =2 306kmDiameter =2 306km

�� Distance to the Sun =Distance to the Sun =

5 906 376 272km5 906 376 272km

ErisEris

�� Diameter =2 600kmDiameter =2 600km

�� Distance to the Sun = 67.665AUDistance to the Sun = 67.665AU

How do we determine how far apart How do we determine how far apart

the planets are?the planets are?

Bode’s Law•A rough rule that predicts the spacing of the planets in the Solar System

•To find the mean distances of the planets, beginning with the following simple sequence of

numbers:

0 3 6 12 24 48 96 192 384

•With the exception of the first two, the others are simple twice the value of the preceding

number.

•Add 4 to each number:

4 7 10 16 28 52 100 196 388

•Then divide by 10:

0.4 0.7 1.0 1.6 2.8 5.2 10.0 19.6 38.8

PlanetPlanet Actual Distance (AU)Actual Distance (AU) BodeBode’’ss LawLaw

MercuryMercury 0.390.39 0.40.4

VenusVenus 0.720.72 0.70.7

EarthEarth 1.001.00 1.01.0

MarsMars 1.521.52 1.61.6

Jupiter Jupiter 5.205.20 5.25.2

SaturnSaturn 9.549.54 10.010.0

UranusUranus 19.219.2 19.619.6

NeptuneNeptune 30.130.1 38.838.8

Works for

moons

too!

What is the Difference Between a What is the Difference Between a

Meteor and a Meteorite?Meteor and a Meteorite?

�� meteoroidmeteoroid is a is a sandsand-- to boulderto boulder--

sized particle of debris in the Solar sized particle of debris in the Solar

SystemSystem

�� meteormeteor is the visible path of a is the visible path of a

meteoroid that enters meteoroid that enters Earth's (or Earth's (or

another body's) atmosphereanother body's) atmosphere

What is an Asteroid?What is an Asteroid?

IAU DefinitionIAU Definition

�� (a) orbits the Sun inside the orbit of (a) orbits the Sun inside the orbit of Jupiter Jupiter

�� (b) does not have sufficient mass for (b) does not have sufficient mass for its selfits self--gravity to overcome rigid gravity to overcome rigid body forces so that it assumes a body forces so that it assumes a hydrostatic equilibrium shape (it is hydrostatic equilibrium shape (it is not round shaped), not round shaped),

�� (c) has not cleared the (c) has not cleared the neighbourhood around its orbit, and neighbourhood around its orbit, and

�� (d) is not a satellite.(d) is not a satellite.

AsteroidsAsteroids�� Small bodies Small bodies

�� Believed to be left over from the beginning of Believed to be left over from the beginning of

the solar system billions of years agothe solar system billions of years ago

�� 100,000 asteroids lie in belt between Mars 100,000 asteroids lie in belt between Mars

and Jupiterand Jupiter

�� Largest asteroids have been given namesLargest asteroids have been given names

�� made of rocky and metallic minerals made of rocky and metallic minerals

�� random shapes random shapes

�� appear more clear than comets appear more clear than comets

when viewed through a telescopewhen viewed through a telescope

Most asteroids are Most asteroids are

located in two located in two

regions:regions:

••Asteroid beltAsteroid belt

••Orbit of JupiterOrbit of Jupiter…… the the

HildasHildas (the orange (the orange

"triangle" just inside "triangle" just inside

the orbit of Jupiter) the orbit of Jupiter)

and the and the Jovian TrojansJovian Trojans

(green). The group (green). The group

that leads Jupiter are that leads Jupiter are

called the "Greeks" called the "Greeks"

and the trailing group and the trailing group

are called the are called the

"Trojans" "Trojans"

Where are the asteroids?

Asteroid BeltAsteroid Belt

�� Discovered in 1801Discovered in 1801

�� Previously Previously

predicted by Franz predicted by Franz

XaverXaver Von ZachVon Zach

�� 18011801-- Piazza found Piazza found

CeresCeres

�� OlbersOlbers found Pallas found Pallas

and and VestaVesta

AsteroidAsteroid BeltBelt

�� The region of space between Mars and Jupiter; The region of space between Mars and Jupiter; about 2.8AUabout 2.8AU

�� Hundreds of thousands of asteroids known. Hundreds of thousands of asteroids known. Probably millions more!Probably millions more!

�� 3 types of asteroid: Carbonaceous, Silicate, 3 types of asteroid: Carbonaceous, Silicate, MetallicMetallic

�� Even the largest object in the belt, Ceres (dwarf Even the largest object in the belt, Ceres (dwarf planet), is too dim to see without aidplanet), is too dim to see without aid

�� Remnants of a planetRemnants of a planet--formation process that formation process that failed due to Jupiterfailed due to Jupiter’’s gravitational pull OR a s gravitational pull OR a planet that was broken apart during a collisionplanet that was broken apart during a collision

What are Comets?What are Comets?

CometsComets

�� Small icy bodiesSmall icy bodies

�� Travel past the SunTravel past the Sun

�� Give off gas and dust as they pass byGive off gas and dust as they pass by

�� made of chemical compounds that made of chemical compounds that vaporize when heated vaporize when heated

�� more elliptical (egg) shapedmore elliptical (egg) shaped

�� appear fuzzier than asteroids when appear fuzzier than asteroids when viewed through a telescopeviewed through a telescope

�� grow tails as they get closer to the Sungrow tails as they get closer to the Sun

�� highly elliptical orbitshighly elliptical orbits

Anatomy of a CometAnatomy of a Comet

Anatomy of a CometAnatomy of a Comet

Parts of a CometParts of a Comet

�� Nucleus= main mass of Nucleus= main mass of

ice/frozen gasice/frozen gas

�� Coma = cloud of gas surrounding Coma = cloud of gas surrounding

nucleusnucleus

�� Tail = forms when ice vaporizes Tail = forms when ice vaporizes

as comet approaches Sunas comet approaches Sun

�� Hydrogen cloud = Hydrogen cloud = cloudcloud of gas of gas

that surrounds coma (only some that surrounds coma (only some

comets have these)comets have these)

http://science.nationalgeographic.com/science/space/solar-system/asteroids-comets-article.html

Where are the comets?Where are the comets?

Kuiper BeltA large body of small objects orbiting (the short period comets <200 years) the Sun in a radial zone extending outward from the orbit of Neptune (30 AU) to about 100 AU. Pluto maybe the biggest of the KuiperBelt object.

Oort CloudLong Period Comets (period > 200 years) seems to come mostly from a spherical region at about 50,000 AU from the Sun.

KuiperKuiper BeltBelt

�� Discovered in 1992Discovered in 1992

�� Named for Dutch Astronomer Gerard Named for Dutch Astronomer Gerard

KuiperKuiper, who had , who had PREDICTEDPREDICTED its its

existence in 1951.existence in 1951.

KuiperKuiper BeltBelt

�� Region beyond Neptune; 30 to over Region beyond Neptune; 30 to over

50AU50AU

�� At least 70,000 small, icy, slowAt least 70,000 small, icy, slow--

moving, objectsmoving, objects

�� Very faint objects because small, far Very faint objects because small, far

and reflect light from Sunand reflect light from Sun

�� A million times fainter than faintest A million times fainter than faintest

we can see with nakedwe can see with naked--eyeeye

OortOort CloudCloud

�� Hypothetical spherical cloud. No Hypothetical spherical cloud. No

direct observations.direct observations.

�� Proposed by Ernst Proposed by Ernst OpikOpik (1932), Jan (1932), Jan

HenrikHenrik OortOort (1950)(1950)

OortOort CloudCloud

�� 50,000AU; defines gravitational boundary 50,000AU; defines gravitational boundary of solar systemof solar system

�� Source of longSource of long--period comets (comets that period comets (comets that have an orbit of hundreds or thousands of have an orbit of hundreds or thousands of years)years)

�� Objects composed of ices (water, Objects composed of ices (water, methane, and ammonia)methane, and ammonia)

�� 2 regions: 2 regions: •• outer sphereouter sphere

•• inner discinner disc

What are the Types of Comets?What are the Types of Comets?

�� ShortShort--period cometsperiod comets

•• periods of less than 200 years, periods of less than 200 years,

•• are returning as predicted on wellare returning as predicted on well--

known orbits known orbits

�� LongLong--period cometsperiod comets

•• periods of more than 200 yearsperiods of more than 200 years

•• among the brightest have been several among the brightest have been several