Download Star Constellations

Star Constellations
Dana Desonie, Ph.D.
Say Thanks to the Authors
Click http://www.ck12.org/saythanks
(No sign in required)
To access a customizable version of this book, as well as other
interactive content, visit www.ck12.org
CK-12 Foundation is a non-profit organization with a mission to
reduce the cost of textbook materials for the K-12 market both
in the U.S. and worldwide. Using an open-content, web-based
collaborative model termed the FlexBook®, CK-12 intends to
pioneer the generation and distribution of high-quality educational
content that will serve both as core text as well as provide an
adaptive environment for learning, powered through the FlexBook
Platform®.
Copyright © 2014 CK-12 Foundation, www.ck12.org
The names “CK-12” and “CK12” and associated logos and the
terms “FlexBook®” and “FlexBook Platform®” (collectively
“CK-12 Marks”) are trademarks and service marks of CK-12
Foundation and are protected by federal, state, and international
laws.
Any form of reproduction of this book in any format or medium,
in whole or in sections must include the referral attribution link
http://www.ck12.org/saythanks (placed in a visible location) in
addition to the following terms.
Except as otherwise noted, all CK-12 Content (including CK-12
Curriculum Material) is made available to Users in accordance
with the Creative Commons Attribution-Non-Commercial 3.0
Unported (CC BY-NC 3.0) License (http://creativecommons.org/
licenses/by-nc/3.0/), as amended and updated by Creative Commons from time to time (the “CC License”), which is incorporated
herein by this reference.
Complete terms can be found at http://www.ck12.org/terms.
Printed: November 9, 2014
AUTHOR
Dana Desonie, Ph.D.
www.ck12.org
C HAPTER
Chapter 1. Star Constellations
1
Star Constellations
• Define constellation.
• Explain the difference between apparent and real distances.
Is this pattern of stars meaningful?
This is a constellation, a pattern of stars in the night sky. This constellation is called Orion. The features you can see
best are his belt and sword. You can see Orion’s belt in the sky from many locations. These stars are very bright.
For many constellations, the stars are not near each other. They just happen to appear near each other in our sky.
Stars
When you look at the sky on a clear night, you can see hundreds of stars. A star is a giant ball of glowing gas that is
very, very hot. A star generates energy by nuclear fusion reactions. Most of these stars are like our Sun. However,
some stars are smaller than our Sun, and some are larger. Except for our own Sun, all stars are so far away that they
only look like single points—even through a telescope.
Constellations
The stars that make up a constellation appear close to each other from Earth. In reality, they may be very distant
from one another. Constellations were important to people, like the Ancient Greeks. People who spent a lot of time
outdoors at night, like shepherds, named the constellations. They told stories about them. Pictured below is one of
the most easily recognized constellations ( Figure 1.1). The ancient Greeks thought this group of stars looked like a
hunter. They named it Orion, after a great hunter in Greek mythology.
The constellations stay the same night after night. The patterns of the stars never change. However, each night the
constellations move across the sky. They move because Earth is spinning on its axis. The constellations also move
with the seasons. This is because Earth revolves around the Sun. The constellations in the winter are different from
1
www.ck12.org
FIGURE 1.1
Orion has three stars that make up his
belt. Orion’s belt is fairly easy to see in
the night sky.
those in the summer. For example, Orion is high up in the winter sky. In the summer, it’s only up in the early
morning.
Constellations are useful. They help astronomers and other observers orient in the night sky. The star Betelgeuse,
for example, is Orion’s right shoulder. Betelgeuse is the eighth brightest star in the sky. The star is an excellent
example of a red supergiant.
Apparent Versus Real Distances
The stars in a constellation appear close together in our night sky. But they are not at all close together out in space.
In the constellation Orion, the stars visible to the naked eye are at distances ranging from just 26 light-years (which
is relatively close to Earth) to several thousand light-years away.
What is Astrology?
Ancient Babylonian astronomers created the Zodiac. The Zodiac is a circle that divides the ecliptic into twelve
30-degree zones. Each zone contains a constellation, many of them animals. Horoscopes based on these astrological
signs first appeared in Ptolemaic Egypt in around 50 BC. These early people used astrology to explain things that
are now much better explained by science. You can see an example of a Zodiac below ( Figure 1.2).
There is no reason to think that the alignment of the stars has anything to do with events that happen on Earth. The
2
www.ck12.org
Chapter 1. Star Constellations
FIGURE 1.2
How did astrology come to be?
constellations are patterns made from stars in the sky. The patterns do not reflect any characteristics of the stars
themselves. When scientific tests are done to provide evidence in support of astrological ideas, the tests fail. When
a scientific idea fails, it is abandoned or modified. Astrologers do not change or abandon their ideas when they fail.
So astrology is not science.
Vocabulary
• constellation: Group of stars that appear to form a pattern in the sky; most often these stars are unrelated and
are not near each other in space. Constellations are used to locate objects in space.
• star: Glowing sphere of gases that produces light through nuclear fusion reactions.
Summary
• The points of light in the night sky are stars that are balls of gas. They are lit by nuclear fusion.
• Constellations are patterns of stars seen from Earth. These stars are usually not near each other.
• Stars in a constellation may be fairly close together. More likely, though, they are extremely far apart.
Explore More
Use the resource below to answer the questions that follow.
• The Universe: The Constellations at http://www.youtube.com/watch?v=QXeEAQtC75g (3:10)
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/1491
1.
2.
3.
4.
5.
6.
What does the word constellation mean?
What are the names of the constellations based on?
What was Orion? Why did the Greeks say the constellation disappeared for part of the year?
Why do constellations change position in the sky?
How many constellations are there?
How do zodiac constellations differ from other constellations?
3
www.ck12.org
Review
1.
2.
3.
4.
Why are constellations so important to people when they think about stars?
Are constellations useful?
Are stars in a constellation close to each other?
What is astrology? How is it different from astronomy?
References
1. IAU and Sky Telescope magazine (Roger Sinnott Rick Fienberg). Star map of the stars in the constellation
orion. CC BY 3.0
2. Courtesy of NASA. An ancient zodiac. Public Domain
4