The Planets

Starter Questions What is a planet? How many planets are there? Where do the planets get their English names from? Why is Earth special?

What is a planet?

How many planets are there?

Where do the planets get their English names from?

Why is Earth special?

Planet Vocabulary Astronomy Astronomer Planet types Terrestrial Gas giants Dwarf planets Elements Composition Atmosphere Crust Mass Gravity Orbit Position “ Years” Axial tilt Relative to sun Rotation Speed of rotation Direction

Astronomy

Astronomer

Planet types

Terrestrial

Gas giants

Dwarf planets

Elements

Composition

Atmosphere

Crust

Mass

Gravity

Orbit

Position

“ Years”

Axial tilt

Relative to sun

Rotation

Speed of rotation

Direction

Vocabulary Part Two Albedo Crater Rings Moon Asteroid belt Mars-Jupiter asteroid belt Kuiper belt Solar system

Albedo

Crater

Rings

Moon

Asteroid belt

Mars-Jupiter asteroid belt

Kuiper belt

Solar system

Outline of Lecture Today, we’ll look at the topic of planets in our solar system We’ll begin by looking at how the solar system was created After that, we’ll take a tour of the solar system Then, we’ll look at the debate over Pluto Finally, we’ll end with a discussion

Today, we’ll look at the topic of planets in our solar system

We’ll begin by looking at how the solar system was created

After that, we’ll take a tour of the solar system

Then, we’ll look at the debate over Pluto

Finally, we’ll end with a discussion

Birth of the Solar System

Theories of the Solar System Early man believed in geocentrism The Earth is the center of the solar system Shown in this picture Science led to the discovery of heliocentrism The Sun is the center of the solar system

Early man believed in geocentrism

The Earth is the center of the solar system

Shown in this picture

Science led to the discovery of heliocentrism

The Sun is the center of the solar system

The Nebular Hypothesis The Sun, like all stars, was born in a giant hydrogen cloud This is called a nebula As the Sun formed, it pulled matter together Some of this matter joined the Sun, some became planets Let’s watch a video

The Sun, like all stars, was born in a giant hydrogen cloud

This is called a nebula

As the Sun formed, it pulled matter together

Some of this matter joined the Sun, some became planets

Let’s watch a video

After the Sun Was Born… Gas giants formed from planets with heavy mass Terrestrial planets formed from lighter planets Smaller planets were destroyed or became moons or asteroids

Gas giants formed from planets with heavy mass

Terrestrial planets formed from lighter planets

Smaller planets were destroyed or became moons or asteroids

What Is a Planet, Anyway? The International Astronomical Union gives us this definition of a planet: A celestial body that is (a) 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 (it is independent). According to this definition, there are only eight planets in our solar system What are they?

The International Astronomical Union gives us this definition of a planet:

A celestial body that is (a) 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 (it is independent).

According to this definition, there are only eight planets in our solar system

What are they?

Order of the Planets Now we have an activity Some of your classmates will represent each of the planets, plus the Sun and Pluto Help your classmates to get into the right order from left to right – from the Sun to the farthest planet away from the Sun

Now we have an activity

Some of your classmates will represent each of the planets, plus the Sun and Pluto

Help your classmates to get into the right order from left to right – from the Sun to the farthest planet away from the Sun

Touring the Solar System

The Terrestrial Planets

The Gas Giants

A Visit to Mercury Closest to the Sun Dimensions Size about 10% of Earth Mass about 5% of Earth Low gravity Composition Almost no atmosphere Silicon-iron crust

Closest to the Sun

Dimensions

Size about 10% of Earth

Mass about 5% of Earth

Low gravity

Composition

Almost no atmosphere

Silicon-iron crust

Features of Mercury Often hard to see Completes an orbit every 88 days Has a small axial tilt Covered in craters, like the Earth’s Moon (see picture) Extremely hot surface Has no moons

Often hard to see

Completes an orbit every 88 days

Has a small axial tilt

Covered in craters, like the Earth’s Moon (see picture)

Extremely hot surface

Has no moons

A Visit to Venus 2 nd closest to the Sun Dimensions Almost the same size as Earth Mass 80% of Earth Gravity 90% of Earth’s Composition Carbon-Nitrogen atmosphere Crust not well known

2 nd closest to the Sun

Dimensions

Almost the same size as Earth

Mass 80% of Earth

Gravity 90% of Earth’s

Composition

Carbon-Nitrogen atmosphere

Crust not well known

Features of Venus Hot Atmosphere filled with clouds of sulfuric acid Very bright, called the “Evening Star” Completes an orbit every 224 days Surface covered by inactive volcanoes No moons

Hot Atmosphere filled with clouds of sulfuric acid

Very bright, called the “Evening Star”

Completes an orbit every 224 days

Surface covered by inactive volcanoes

No moons

A Visit to Mars 4 th from the Sun Dimensions About half the size of Earth Mass 10% of Earth Gravity 38% of Earth Composition Light Carbon-Nitrogen atmosphere Basalt and iron crust

4 th from the Sun

Dimensions

About half the size of Earth

Mass 10% of Earth

Gravity 38% of Earth

Composition

Light Carbon-Nitrogen atmosphere

Basalt and iron crust

Features of Mars Light atmosphere with polar ice caps Evidence of liquid water on surface Home to largest volcano in solar system, Olympus Mons (shown) Has two moons

Light atmosphere with polar ice caps

Evidence of liquid water on surface

Home to largest volcano in solar system, Olympus Mons (shown)

Has two moons

Phobos and Deimos Mars’ moons are two large asteroids They’re much smaller than the Moon Their names also come from Greek myth Phobos, the demigod of fear Deimos, the demigod of terror

Mars’ moons are two large asteroids

They’re much smaller than the Moon

Their names also come from Greek myth

Phobos, the demigod of fear

Deimos, the demigod of terror

A Visit to Jupiter 5 th from the Sun Dimensions 2.5 times bigger than all the planets combined Mass 300 times Earth Composition Hydrogen atmosphere Metallic hydrogen crust

5 th from the Sun

Dimensions

2.5 times bigger than all the planets combined

Mass 300 times Earth

Composition

Hydrogen atmosphere

Metallic hydrogen crust

Features of Jupiter Jupiter is a small, unfinished star Famous for giant red spot (shown) Has extremely powerful gravity Surrounded by a light series of rings and many moons

Jupiter is a small, unfinished star

Famous for giant red spot (shown)

Has extremely powerful gravity

Surrounded by a light series of rings and many moons

Jovian Moons Jupiter has more than 60 moons The most famous are the four discovered by Galileo (shown) Io Europa Ganymede Callisto

Jupiter has more than 60 moons

The most famous are the four discovered by Galileo (shown)

Io

Europa

Ganymede

Callisto

A Visit to Saturn 6 th from the Sun Dimensions 2 nd biggest planet in the solar system Mass 95 times Earth Strong gravity Composition Hydrogen atmosphere Icy hydrogen core Rings made of ice and rock

6 th from the Sun

Dimensions

2 nd biggest planet in the solar system

Mass 95 times Earth

Strong gravity

Composition

Hydrogen atmosphere

Icy hydrogen core

Rings made of ice and rock

Features of Saturn Famous for a brilliant series of rings around the planet Like Jupiter, also a failed star North pole covered by a rotating hexagonal cloud Home to many moons

Famous for a brilliant series of rings around the planet

Like Jupiter, also a failed star

North pole covered by a rotating hexagonal cloud

Home to many moons

Saturnian Moons Like Jupiter, Saturn has more than 60 moons The moons are a mix of compositions, such as silica, water ice, iron, and so on Some are dwarf planets, like Titan

Like Jupiter, Saturn has more than 60 moons

The moons are a mix of compositions, such as silica, water ice, iron, and so on

Some are dwarf planets, like Titan

A Visit to Uranus 7 th from the Sun Dimensions 14.5 times bigger than Earth Large but not dense Composition Hydrogen-Helium atmosphere Ammonia ice and water ice in core

7 th from the Sun

Dimensions

14.5 times bigger than Earth

Large but not dense

Composition

Hydrogen-Helium atmosphere

Ammonia ice and water ice in core

Features of Uranus Has a ring system (shown) Atmosphere has less features than the other gas giants Home to almost 30 moons Discovered in modern times because the planet is dimly lit

Has a ring system (shown)

Atmosphere has less features than the other gas giants

Home to almost 30 moons

Discovered in modern times because the planet is dimly lit

Moons of Uranus

A Visit to Neptune 8 th from the Sun Dimensions Seventeen times bigger than Earth Composition Hydrogen-Helium atmosphere Methane gives the planet a blue color Icy core

8 th from the Sun

Dimensions

Seventeen times bigger than Earth

Composition

Hydrogen-Helium atmosphere

Methane gives the planet a blue color

Icy core

Features of Neptune Combines features of Jupiter and Saturn Has a ring system and a series of “spots” – storms in the atmosphere Has 13 known moons Largest is called Triton Neptune is often difficult to see without a telescope

Combines features of Jupiter and Saturn

Has a ring system and a series of “spots” – storms in the atmosphere

Has 13 known moons

Largest is called Triton

Neptune is often difficult to see without a telescope

The Pluto Debate

Background Information Pluto is the largest object in the Kuiper belt It is primarily made of rock and ice and has its own moon, Charon For 76 years, Pluto was considered a planet In 2006, Pluto was reclassified as a dwarf planet Note: there are no photographs of Pluto

Pluto is the largest object in the Kuiper belt

It is primarily made of rock and ice and has its own moon, Charon

For 76 years, Pluto was considered a planet

In 2006, Pluto was reclassified as a dwarf planet

Note: there are no photographs of Pluto

Pluto and Dwarf Planets

Discussion

Discussion Questions Do you think there might be life on any other planets in our solar system? Do you think we’ll ever find another Earth? Will we ever live on the Moon? Should we send a man to Mars? Should we try and change Mars or Venus to make them like Earth? Can the position of planets influence our life?

Do you think there might be life on any other planets in our solar system?

Do you think we’ll ever find another Earth?

Will we ever live on the Moon?

Should we send a man to Mars?

Should we try and change Mars or Venus to make them like Earth?

Can the position of planets influence our life?