Objects in Our Solar System

Vers. 08/2020 © Kesler Science, LLC

Planets and
Gravity

© Kesler Science, LLC

Planets and Gravity

Essential Questions:

Reflect on the
Essential Questions
before you dive in…

1. If you were quizzed
today, which questions
would you know the
answers to already?

2. Which questions would
you need to learn more
about to answer
confidently?

1.

Can you describe the
physical properties of
planets and their
location?

2.

Can you describe the
movements of the
sun, the planets and
the Galilean moons?

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Planets and Gravity

Planet:
A celestial body moving in an elliptical orbit around a star

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Some Planet
Characteristics
Include:
• Color
• Proximity to Sun
• Size
• Speed
• Density
• Physical/Chemical

make up

​

Planets and Gravity

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Planets and Gravity

Inner Planets
(compared to Outer
Planets)

• Mercury, Venus, Earth, Mars

• Closer together
• Terrestrial, rocky
• More dense

• Smaller
• Shorter revolution

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Outer Planets
(compared to Inner Planets)

• Jupiter, Saturn, Neptune, Uranus

• Farther apart
• Made up mostly of gas
• Less dense

• Larger
• Longer revolution

• Less is known about them

Why do you think

less is known about
the outer planets?

Categorize

Options (8)

Mercury

Venus

Earth

Mars

Jupiter

Saturn

Uranus

Neptune

Organize these options into the right categories

Inner Planet

Outer Planet

Labelling

Label the planets.

Drag labels to their correct position on the image

Venus

Mercury

Earth

Neptune

Uranus

Saturn

Mars

Jupiter

Labelling

Label the planets.

Drag labels to their correct position on the image

Mars

Uranus

Saturn

Venus

Mercury

Neptune

Jupiter

Earth

Multiple Choice

The inner planets are smaller and closer together.

• True

• False

Multiple Choice

The inner planets are made of gas.

• True

• Falce

Fill in the Blank

A celestial body moving in an elliptical orbit around a star is called a _____.

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Planets and Gravity

A natural force of attraction exerted by
a celestial body on the mass of objects
that are on or near its surface

What is Gravity?

What is Gravity?

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Planets and Gravity

How does the mass of an object affect gravity?

The greater the mass of an
object, the more gravitational
force is exerted on other
objects around it.

How does the mass of an
object affect the gravity?

Multiple Choice

Would your mass change if you travelled to another planet?

• Yes

• No

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Planets and Gravity

The Sun’s gravity is what causes the planets
to orbit in our solar system.

Image not to scale

What force governs all planetary
movement in the solar system?

What force governs all planetary movement in the solar

system?

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Planets and Gravity

The closer the two objects are the more
gravitational force they have.

• Ex: The Moon has a much larger impact on our

tides than the Sun does

How does the distance between two
objects affect the force of gravity?

How does the distance between two objects affect the

force of gravity?

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Planets and Gravity

How do planets move?

• Planets orbit (revolve) counter-clockwise around the Sun

• All planets spin on their axis (rotate) counter-clockwise

(except for Venus and Uranus).

• The Sun’s gravity keeps them in their orbits

• The planets’ orbits are elliptical shaped

Multiple Choice

To spin on an axis...

• rotation

• revolution

Fill in the Blank

To move around another object

Fill in the Blank

The force that keeps objects moving around the Sun.

Multiple Choice

The closer the objects are together, the stronger the gravitational force is.

• True

• False

Fill in the Blank

The shape of a planets orbit is ____.

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Mercury
• Closest planet to the

Sun

• Smallest planet in

solar system

• 2nd hottest planet

• No atmosphere

• Revolution takes

88 Earth days

• Craters

Spacecraft MESSENGER (NASA) has been surveying Mercury’s minerals
and surface, using their Visual and Infrared Spectrometer (VIRS).

Image Credit: NASA/Johns Hopkins Univ. Applied Physics Laboratory/Carnegie Inst. of

Washington

List 2

characteristics

of Mercury.

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Planets and Gravity

Venus
• 2nd closest planet to the Sun
• “Sister” to Earth in size
• Thick atmosphere
• Hottest planet because of

Greenhouse Effect

• Revolution 225 Earth days, making

its “day” (243 Earth days) longer
than its year

List 2 characteristics of Venus.

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Planets and Gravity

Earth
• Our home
• Made of 2/3 water
• Only planet known to support life
• Has a magnetosphere which deflects harmful

electromagnetic rays from the Sun

• Revolution every 365 1/4 Earth days

The Moon moving over the Pacific Ocean
near North Americaas seen by the Deep
Space Climate Observatory (DSCOVR)
spacecraft.

Source: NASA/NOAA

List 2 characteristics of Earth.

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Planets and Gravity

Mars
• The “red planet”

• Grand Canyon of Mars

dwarfs Earth’s Grand Canyon

• Largest dust storms

• Unmanned rovers currently

exploring Mars

• Revolution 687 Earth days

Panorama from the rover Pathfinder at Ares Vallis

Image Credit: NASA/JPL
List 2 characteristics of Mars.

Multiple Choice

The hottest planet...

• Mercury

• Venus

• Earth

• Mars

Multiple Choice

The Red Planet...

• Mercury

• Venus

• Earth

• Mars

Multiple Choice

Has a day that is longer than it's year...

• Mercury

• Venus

• Earth

• Mars

Multiple Choice

Has no atmosphere...

• Mercury

• Venus

• Earth

• Mars

Multiple Choice

Earth's 'Sister planet'

• Mercury

• Venus

• Earth

• Mars

Multiple Choice

Has a revolution of 365 1/4 days...

• Mercury

• Venus

• Earth

• Mars

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Planets and Gravity

Jupiter

• Largest planet
• Great Red Spot can fit 2 Earth’s inside it
• Galileo discovered many of Jupiter’s moons
• Ganymede is the largest moon in the solar

system.

• Revolution 12 Earth years

List 2 characteristics of

Jupiter.

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Saturn
• Many rings made of

dust and ice

• Low density – could

float in a bathtub if one
were big enough

• Revolution 29 Earth

years

List 2 characteristics of Saturn.

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Planets and Gravity

Uranus
• Axis is sideways and

rotates north and south

• Thirteen sets of rings,

some partial

• Voyager 2 passed by
• Revolution 84 Earth

years

Images of the planet Uranus taken

by the spacecraft Voyager 2 in 1986.

Image Credit: NASA/JPL

List 2 characteristics of

Uranus.

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Planets and Gravity

Neptune
• Smaller than Uranus

but with greater mass

• Has a Great Dark Spot similar to

Jupiter's Great Red Spot

• Voyager 2 passed by it in 1989

• Revolution 165 Earth years

Voyager 2 captures the rings of Neptune

List 2 characteristics of Neptune.

Multiple Choice

Axis is turned sideways...

• Jupiter

• Saturn

• Uranus

• Neptune

Multiple Choice

Density is so low it would float...

• Jupiter

• Saturn

• Uranus

• Neptune

Multiple Choice

Largest planet

• Jupiter

• Saturn

• Uranus

• Neptune

Multiple Choice

Has the Great Dark Spot

• Jupiter

• Saturn

• Uranus

• Neptune

Multiple Choice

Has the Great Red Spot

• Jupiter

• Saturn

• Uranus

• Neptune

Multiple Choice

Farthest planet from the Sun

• Jupiter

• Saturn

• Uranus

• Neptune

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Planets and Gravity

Galilean Moons: Io
• Innermost moon to Jupiter

• Highest density

• Driest and most geologically active

object in the solar system

Image Credit: NASA's Goddard Space Flight Center Cover image courtesy of NASA/JPL/University of Arizona

NASA’s New Horizons spacecraft caught a volcanic

explosion on Io, Jupiter’s third-largest moon

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Planets and Gravity

Galilean Moons: Europa
• Smallest of Galilean Moons
• Smoothest surface of any known

solid object in the solar system

Source: NASA/JPL-Caltech/SETI Institute

“Ocean Moon” – astronomers believe there is
saltwater ocean under Europa’s icy crust

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Planets and Gravity

Galilean Moons: Callisto
• Almost as big as Mercury
• Same hemisphere always faces Jupiter
• Heavily cratered

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Planets and Gravity

Galilean Moons: Ganymede
• Largest moon in the solar system

(8% larger than Mercury)

• Underground ocean and magnetic

field

• First observed by Galileo in 1610

Naturally colored Ganymede moon, as

seen from Galileo spacecraft

Give your best answer to...

1.

Describe the physical properties of the planets and
their locations.

2.

Describe the movements of the sun, the planets, and
the Galilean moons.

Check for

Understanding

Still have
questions?

Which essential questions do you still need help to understand?