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Galaxies
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Printed: November 16, 2013
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C ONCEPT
Concept 1. Galaxies
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Galaxies
Lesson 26.2: True or False
Name___________________ Class______________ Date________
Write true if the statement is true or false if the statement is false.
_____ 1. There are a total of about 5 million galaxies in the universe.
_____ 2. Star clusters contain greater numbers of stars than galaxies do.
_____ 3. The Pleiades, or Seven Sisters, is an example of a star cluster.
_____ 4. Globular clusters have a lot of dust in addition to stars.
_____ 5. The Andromeda Galaxy is an example of an irregular galaxy.
_____ 6. The reason we can’t see many dwarf galaxies is that they are so distant.
_____ 7. The Milky Way Galaxy has a disk and central bulge.
_____ 8. Our solar system is at the outermost edge of our galaxy.
_____ 9. Constellations are binary or multiple star systems.
_____ 10. More than half of the bright stars we see in our galaxy are actually star systems.
Lesson 26.2: Critical Reading
Name___________________ Class______________ Date________
Read this passage based on the text and answer the questions that follow.
Types of Galaxies
Galaxies are the biggest groups of stars in the universe. They can contain anywhere from a few million to many
billions of stars. Galaxies are divided into three types according to shape: spiral, elliptical, and irregular galaxies.
• Spiral galaxies spin and appear as a rotating disk of stars and dust, with a bulge in the middle. Several spiral
arms reach outward from the central bulge like the arms of a pinwheel. Spiral galaxies have lots of gas and
dust. Most of their stars are young and blue in color.
• Elliptical galaxies are more-or-less egg shaped. The smallest elliptical galaxies are as small as some globular
clusters. The largest elliptical galaxies can contain over a trillion stars. Most stars in elliptical galaxies are
reddish to yellowish in color because they are old stars. Most elliptical galaxies contain very little gas and
dust because these particles have already formed into stars.
• Irregular galaxies are neither elliptical nor spiral in shape. Most irregular galaxies were once spiral or elliptical
galaxies that were then deformed. This may have happened by gravitational attraction to a larger galaxy or by
collision with another galaxy.
Dwarf galaxies are small galaxies containing only a few million or billion stars. Dwarf galaxies are the most common
type of galaxies in the universe. However, because they are small, they are also dim, so we don’t see very many
dwarf galaxies from Earth. Most dwarf galaxies are irregular in shape. However, there are also dwarf elliptical
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galaxies and dwarf spiral galaxies. Dwarf galaxies are often found near larger galaxies. They sometimes collide and
merge with their larger neighbors.
Questions
1. What are galaxies?
2. Compare and contrast spiral, elliptical, and irregular galaxies.
3. Describe dwarf galaxies.
Lesson 26.2: Multiple Choice
Name___________________ Class______________ Date________
Circle the letter of the correct choice.
1. Stars in an open cluster are generally
a.
b.
c.
d.
red.
old.
from the same nebula.
two of the above
2. Groups of stars that contain the greatest numbers of stars are
a.
b.
c.
d.
globular clusters.
open clusters.
star systems.
galaxies.
3. Types of galaxies by shape include
a.
b.
c.
d.
dwarf galaxies.
elliptical galaxies.
regular galaxies.
all of the above
4. Dwarf galaxies are
a.
b.
c.
d.
relatively rare.
not very bright.
mostly spiral shaped.
two of the above
5. The Milky Way Galaxy
a.
b.
c.
d.
is a dwarf galaxy.
is an elliptical galaxy.
has spiral arms.
has 1 to 2 million stars.
6. Which statement(s) about irregular galaxies is (are) true?
a.
b.
c.
d.
Most were once spiral or elliptical galaxies.
They became irregular when they were deformed.
They were changed by gravity or a collision.
all of the above
7. Globular clusters
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a.
b.
c.
d.
Concept 1. Galaxies
are spherical in shape.
contain mostly blue stars.
have widely spaced stars.
contain billions of stars.
Lesson 26.2: Matching
Name___________________ Class______________ Date________
Match each definition with the correct term.
Definitions
_____ 1. group of up to a few thousand stars held loosely together by gravity
_____ 2. type of galaxy that forms a rotating disk
_____ 3. group of many thousand stars held tightly together by gravity
_____ 4. type of galaxy that is shaped like an egg
_____ 5. type of galaxy that is most common in the universe
_____ 6. any group of millions, billions, or even trillions of stars
_____ 7. type of galaxy that has no definite shape
Terms
a. dwarf galaxy
b. elliptical galaxy
c. globular cluster
d. irregular galaxy
e. open cluster
f. spiral galaxy
g. galaxy
Lesson 26.2: Fill in the Blank
Name___________________ Class______________ Date________
Fill in the blank with the appropriate term.
1.
2.
3.
4.
5.
6.
7.
Our solar system is located in the __________ Galaxy.
A set of stars that are grouped closely together is called a star __________.
Hundreds or thousands of stars that are grouped closely together make up a star __________.
A system of two stars orbiting each other is called a(n) __________.
A spiral galaxy has projections called __________.
Based on its shape, the Milky Way Galaxy is classified as a(n) __________ galaxy.
At the center of most galaxies is a supermassive __________.
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Lesson 26.2: Critical Writing
Name___________________ Class______________ Date________
Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.
Explain how scientists determined the shape of the Milky Way Galaxy, including the types of evidence they used.
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