CHAPTER 23 The Planets & The Solar System. The Inner Planets - Mercury, Venus, Earth, and MarsInner Planets- Mercury, Venus, Earth, and Mars Called planets.

CHAPTER CHAPTER 2323

The The Planets Planets & The & The Solar Solar

SystemSystem

The Inner PlanetsThe Inner Planets

• Inner Planets- Mercury, Venus, - Mercury, Venus, Earth, and MarsEarth, and Mars

• Called Called Terrestrial planets planets Terra means Earth so… EarthlikeTerra means Earth so… Earthlike

• These planets have a These planets have a rocky crust, , denserdenser mantle, and , and very dense core

MERCURMERCURYY

VENUSVENUS

EARTHEARTH

MARSMARS

The “Grand Canyon” of Mars – Valles Marineras The “Grand Canyon” of Mars – Valles Marineras

It’s length is the distance from NY to California!It’s length is the distance from NY to California!

It’s widest point is the distance from NY to Georgia!It’s widest point is the distance from NY to Georgia!

Mars sure looks a lot like Arizona, eh?Mars sure looks a lot like Arizona, eh?

The Outer PlanetsThe Outer Planets

• Outer Planets- Jupiter, Saturn, Uranus and - Jupiter, Saturn, Uranus and NeptuneNeptune

• Called Called Jovian planets (Jupiter-like) planets (Jupiter-like)

• These planets are much These planets are much larger, more , more gaseous, and , and less dense than the inner than the inner planets planets

• Pluto is not an outer planet as it 1) is not Pluto is not an outer planet as it 1) is not Jovian and 2) does not meet the new criteria Jovian and 2) does not meet the new criteria of the definition of a planet so scientists have of the definition of a planet so scientists have deleted Pluto from their list of Planets…now deleted Pluto from their list of Planets…now it’s a Dwarf Planetit’s a Dwarf Planet

JUPITERJUPITER

IoIo

EuropEuropaa

CalistoCalisto

GanymedeGanymede

The Galilean Moons – The Galilean Moons – The Largest of the 63 The Largest of the 63 Moons of JupiterMoons of Jupiter

SATURNSATURN

The The Largest Largest

of the 57 of the 57 Moons of Moons of Saturn – Saturn – NOT TO NOT TO

SCALE!!!!SCALE!!!!

URANUURANUSS

Uranus and 5 of its 27 moons!Uranus and 5 of its 27 moons!

NEPTUNNEPTUNEE

NeptunNeptune has e has

13 13 MoonsMoons

PLUTO –PLUTO – the oddball• On August 24, 2006, 424 of the world’s On August 24, 2006, 424 of the world’s

astronomers (less than 5% astronomers (less than 5% ) voted on ) voted on a new definition of a planet. a new definition of a planet.

• Because of the path of Pluto’s orbit and Because of the path of Pluto’s orbit and size, it is now considered a “Dwarf size, it is now considered a “Dwarf Planet”Planet”

• The following is the International The following is the International Astronomical Union’s (IAU) definition of Astronomical Union’s (IAU) definition of planet, dwarf planet and other objects planet, dwarf planet and other objects in the Solar System.in the Solar System.

RESOLUTION 5AThe IAU therefore resolves that planets and other bodies in our Solar System be defined into three distinct categories in the following way:(1) 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 neighborhood around its orbit. (the planet’s orbit doesn’t cross another planet’s orbit…this is where Pluto doesn’t “make the cut”…)(2) 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) shape, (c) has not cleared the neighborhood around its orbit, and (d) is not a satellite.(3) All other objects orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".

Data on the planets is Data on the planets is located in your Handy located in your Handy

Dandy ESRT’s, page 15Dandy ESRT’s, page 15 (Basically, everything you

ever wanted to know about the Planets that NYS can

ask you about is right there at your fingertips…)

Comets, Asteroids, and

Meteoroids

COMETSCOMETS

• masses of masses of rock, dust, ice and gases that revolve around the sun that revolve around the sun in their own orbitsin their own orbits

• orbits are usually very orbits are usually very eccentric (stretched out), which means that (stretched out), which means that one complete orbit of the sun may one complete orbit of the sun may take many years take many years – Ex. Halley’s Comet is only viewable Ex. Halley’s Comet is only viewable

on Earth every 76 years! It will next on Earth every 76 years! It will next appear to us in the year 2062!appear to us in the year 2062!

Comet Hyakutake  Comet Hale-Bopp

Comet Tails always point away from the Sun. Gas (Ion) tails point straight away from the Sun. Dust tails curves toward the orbital path.

Orbit of Comet

Tails get longer the closer the comet gets to the Sun.

ION TAIL

DUST TAIL

ION TAIL

DUST TAIL

The orbit of Haley’s Comet is highly eccentric, The orbit of Haley’s Comet is highly eccentric, and therefore the comet can only be seen on and therefore the comet can only be seen on

Earth every 72 years!Earth every 72 years!

ASTEROIDSASTEROIDS

• Solid chunks of rock in space in space• Most asteroids are found in a Most asteroids are found in a nearly

circular orbit between Mars and between Mars and Jupiter, revolving in the Jupiter, revolving in the same direction as the planets do as the planets do– This orbital cluster is called the This orbital cluster is called the

Asteroid beltAsteroid belt• A few are large, but most asteroids A few are large, but most asteroids

are less than 1 meter long!are less than 1 meter long!

The Inner Planets and the Sun are in the tiny circle right here…

METEOROIDSMETEOROIDS

• Fragments of rocks or ice traveling traveling through spacethrough space

• Occasionally, these fragments may get Occasionally, these fragments may get pulled into Earth’s atmosphere by its pulled into Earth’s atmosphere by its gravitygravity

• As the meteoroid shoots through the As the meteoroid shoots through the atmosphere, atmosphere, friction causes heat to build up and the meteoroid begins to glow– The object is now called a The object is now called a METEOR

(shooting star) (shooting star)

• Sometimes many meteoroids enter our Sometimes many meteoroids enter our atmosphere at one time, this is called a atmosphere at one time, this is called a meteor shower

• If the meteor survives its trip through If the meteor survives its trip through the atmosphere and hits the Earth’s the atmosphere and hits the Earth’s surface, it is then called a surface, it is then called a meteorite

• Impact craters are “potholes” in the are “potholes” in the Earth’s crust caused by meteorites Earth’s crust caused by meteorites hitting the ground with great speed and hitting the ground with great speed and forceforce– Ex. the Barringer Crater in Arizona (1,300m Ex. the Barringer Crater in Arizona (1,300m

wide, 200m deepwide, 200m deep).).

METEOROIDSMETEOROIDS

Question of the Day…Question of the Day…

Why are there so many Why are there so many more craters on the more craters on the moon than on the Earth? moon than on the Earth? There’s a couple of There’s a couple of explanations – but they explanations – but they are all a result of the are all a result of the same reason…same reason…