Galaxy Lesson

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What are galaxies?

Photo credit: NASA/Getty Images

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What are galaxies? continued

Our solar system is made up of a single star, planets, rocks, and dust
particles. Billions of similar stars and star systems surround us. They
make up a galaxy, a huge group of stars, dust, gas, planets, and other
objects bound by gravity.

Photo credit: NASA/Getty Images

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Galaxy Organization

THEME Systems Use the image bank to show the parts of a
galaxy in order of increasing size.

Star

Galaxy

Star System

1

2

3

Photo credit:s GSFC/SDO/NASA; Triff/Shutterstock; Sciepro/Science Photo Library/Getty Images

Image Bank

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Galaxy Organization Answers

THEME Systems Use the image bank to show the parts of a
galaxy in order of increasing size.

Photo credit:s GSFC/SDO/NASA; Triff/Shutterstock; Sciepro/Science Photo Library/Getty Images

Image Bank

Star

Galaxy

Star System

1

Star

2

Star

system

3

Galaxy

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How can galaxies be categorized?

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How can galaxies be categorized? continued

Spiral

Elliptical

Astronomers categorize galaxies based on structure and star
arrangement. Spiral galaxies have a bulge in the center and arms
that spiral outward. Elliptical galaxies are shaped like round or
flattened balls, and they contain mostly old stars. Irregular galaxies
do not have regular shapes.

Irregular

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Categorizing Galaxies

Categorize Identify each galaxy pictured as spiral, elliptical,
or irregular.

Photo credits: NASA Image Collection/Alamy Stock Photo; B.A.E. Inc./Alamy Stock Photo; NASA Image Collection/Alamy Stock Photo

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Categorizing Galaxies Answers

Categorize Identify each galaxy pictured as spiral, elliptical,
or irregular.

Photo credits: NASA Image Collection/Alamy Stock Photo; B.A.E. Inc./Alamy Stock Photo; NASA Image Collection/Alamy Stock Photo

irregular

spiral

elliptical

irregular

spiral

elliptical

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Where is Earth’s solar system located in
the Milky Way galaxy?

Photo credit: NASA Image Collection/Alamy Stock Photo

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Where is Earth’s solar system located in
the Milky Way galaxy? continued

The Milky Way galaxy is
a barred spiral galaxy. It
has a bar-shaped area
of stars and gas at the
center and two main
spiral arms.

Our solar system is
about 26,000 light-years
away from the galaxy’s
center, on the edge of
the smaller Orion Arm.

Photo credit: NASA Image Collection/Alamy Stock Photo

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Locating the Solar System

SEP Use Models Identify
the correct location of
Earth’s solar system in the
Milky Way.

Photo credit NASA Image Collection/Alamy Stock Photo

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Locating the Solar System Answers

SEP Use Models Identify
the correct location of
Earth’s solar system in the
Milky Way.

X

Photo credit NASA Image Collection/Alamy Stock Photo

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Exit Ticket

Suppose a visitor from a nearby galaxy
wants to tour our solar system. Choose
one of the following ways to describe
how to find our solar system in the Milky
Way galaxy.

1.

Draw a space “road map” of our
galaxy with labels.

2.

Write an intergalactic email with
detailed directions.