Chapter 11 discusses the structures of the solar system, defining key vocabulary such as asteroids, comets, and the astronomical unit. It explains the sun's central role as the largest object, along with the classification of planets and dwarf planets, while also addressing the differences between inner and outer planets. The chapter concludes with an overview of planetary motion, including concepts of revolution, rotation, and elliptical orbits.

1. Chapter 11 Lesson 1: The Structures of the Solar System – p. 374-380 – page 1
Vocabulary
• Asteroid (377) – millions of small, rocky objects that orbit the Sun in the asteroid belt
between the orbits of Mars and Jupiter.
• Comet (377) – an object made of gas, dust, and ice and moves around the Sun in an oval-
shaped orbit
• Astronomical Unit (AU) (378) – the average distance from Earth to the Sun – about 150
million km
• Period of Revolution (378) – the time it takes and object to travel once around the Sun
• Period of Rotation (378) – the time it takes an object to complete one rotation
What is the solar system?
• When looking at the night sky, you will likely see stars and
planets. Sometimes, the first star-like object you see at
night is not a star at all.
• A few of the tiny lights that you can see are part of our
_______________________.
• Almost all of the other specks of light
are______________.
Objects in the Solar System
• Ancient observes looking at the night sky saw many stars but only
five______________________– Mercury, Venus, Mars, Jupiter, and Saturn.
• The invention of the _____________________in the 1600s led to the
discovery of additional planets and many other space objects.
The Sun
• The ____________________object in the solar system is the Sun, a star.
• Its diameter is about ________________________ km.
• Its made mostly of ___________________ gas
• Its mass makes up about _______________ percent of the entire
___________ of the solar system
• Inside the Sun, a process called nuclear ____________________produces
an enormous amount of energy.
• Some of the energy is emitted as ___________________
• The Sun also applies ____________________________ forces to objects in the solar system.
• Gravitational forces cause the planets and other objects to move around,
or_______________, the Sun.
Objects That Orbit the Sun
• Planets, dwarf planets, _____________________, and comets orbit the Sun.
• These ______________ emit light.
• Planets
• An object is a planet only if it orbits the Sun and
has a nearly _______________________ shape.
• The mass of a planet must be much
_________________ than the total mass of all

2. Chapter 11 Lesson 1: The Structures of the Solar System – p. 374-380 – page 2
other objects whose orbits are close by.
• Our solar system has _______________________ objects classified as planets.
• Inner Planets and Outer Planets
• The four planets closet to the Sun are the ____________________ planets.
• _______________________________________________________________________
• These planets are mainly made of ________________________ rocky materials
• The four planets farthest from the Sun are called the _____________________ planets
• ______________________________________________________________________
• These planets are mainly made of ice and gases such as
________________and___________________.
• Because they are much larger than Earth, we also call them ___________________.
• Dwarf Planets
• A ________________ planet is a spherical object that
orbits the Sun.
• It is not a ___________________ of another planet
and is in a region of the solar system where there are
many objects orbiting ________________ it.
• Unlike a planet, a dwarf planet does not have more
__________________ than objects in nearby orbits
• They are made of rock and ice and are much
____________________ than Earth.
• They include Ceres, Eris, Pluto, and__________________________.
• Asteroids
• Millions of small, rocky objects called asteroids orbit the Sun in the
asteroid belt between the orbits of _______________ and Jupiter
• They range in size from less than a __________________ to
several hundred kilometers in length
• Unlike planets and dwarf planets, asteroids usually aren’t
__________________________
• Comets
• A comet is made of________________, dust, and
ice and moves around the Sun in an
________________-shaped orbit.
• Comets come from the ________________
parts of the solar system.
• There might be __________________comets
orbiting the Sun.
The Astronomical Unit
• On Earth we use meters or_____________.
• Objects in the solar system, are so far apart that astronomers use a larger distance unit.
• An __________________________________________________(AU) is the average distance
from Earth to the Sun – about 150 million km.

3. Chapter 11 Lesson 1: The Structures of the Solar System – p. 374-380 – page 3
The Motion of the Planets
• Revolution and Rotation
• The time it takes an object to travel once around
the Sun is its period of ___________________
• Earth’s period of revolution is one__________.
• The time it takes an object to complete one
rotation is its period of _____________________
• Earth’s period of rotation is one _________
• Planetary Orbits and Speeds
• Unlike a ball swinging on the end of a string, planets do not move in ________________
• Instead, a planet’s orbit is an__________________
– a stretched-out circle
• Inside an ellipse are two special points, each
called a_____________________.
• These focus points, or foci, determine the
__________________ of the ellipse.
• The foci are ___________________ distances
from the center of the ellipse.
• A planet’s ________________also changes as it
orbits the Sun. The ___________________the
planet is to the Sun, the ________________________it moves.
• This also means that planets farther from the Sun have longer periods
of_______________________.
• For example, Jupiter is more than 5 times farther from the Sun
than_______________.
• It takes Jupiter _______________ times longer than Earth to revolve around
the Sun.