Download FREE Sample Here

C H A P T E R
2
THE SKY
CHAPTER OUTLINE
2-1
2-2
The Stars
Constellations
The Names of the Stars
The Brightness of Stars
Reasoning with Numbers 2-1
Magnitudes
The Sky and Its Motion
The Celestial Sphere
The Sky Around Us
Window on Science 2-1
Scientific Arguments: The Structure of Science
Precession
Window on Science 2-2
Frameworks for Thinking about Nature: Scientific Models
Window on Science 2-3
Understanding Versus Naming: The True Goal of Science
KEY CONCEPTS
This chapter focuses on the appearance of the night sky. Many of the concepts presented were
common knowledge before time became quantified on clocks and city lights blocked our nightly view of the
sky. Most people today no longer have an understanding of the basic appearance or motions of the sky.
The three Window on Science (WOS) discussions in this chapter present very important concepts in
all sciences. WOS 2-1 focuses on the development of scientific arguments. It is important to emphasize
here that science is not about who is right but about what explanation is most correct. Scientific arguments
need to address all possible data and theories so that the best scientific explanation can be formulated. WOS
2-2 presents the concept of a scientific model and should be stressed. It is important to understand that
scientific models do not have to be 100% accurate, 100% of the time to be useful. The discussion of the
celestial sphere as a scientific model points out both the usefulness and limitations inherent in most scientific
models. Other more familiar models might be briefly discussed as examples of scientific models (e.g. Bohr
model of the atom). The concepts of model, theory, and hypothesis are used consistently and coherently
throughout the book.
The WOS 2-3 discusses the difference between naming something, or knowing the name of
something, and understanding the process, object or phenomena. An excellent example of this is a star.
Most people can point to a star when asked what one is, but few can give a reasonably clear definition of
one, describe what it is made of, how it produces energy, and/or how it changes with time. This illustrates
that most people know that the name for one of those little points of light is "star,” but their understanding of
stars ends there. The goal of science is not to name or memorize the names of objects, processes or
phenomena, but instead to understand what they are and how they operate.
One topic presented in this chapter that is confusing for many students is the magnitude of a star. It
is important to cover this topic because magnitudes will be used in later chapters. Most Hertzsprung-Russell
diagrams used in connection with stellar evolution employ absolute visual magnitude, so the magnitude
system will be encountered again.
Finally, this chapter uses numerous diagrams and pictures to communicate critical information.
Emphasize the importance of looking at the figures and reading the figure captions. Astronomy is a visual
10
Chapter 2
Full file at http://testbank360.eu/solution-manual-horizons-10th-edition-seeds
science and pictures greatly add to the understanding of a concept. Think of a picture as a miniature
scientific model. One of the things that many of us who teach general education science courses believe we
do is to help students learn to critically observe pictures and learn to read graphs and charts. Yet, few of us
test this skill. Several of the exam questions in the test bank make use of pictures, tables, and graphs. It will
help the students greatly in the course, and their development of critical reading skills, if they know at the
beginning that understanding the diagrams, pictures, charts, and graphs is important and something they will
be tested on.
Demonstration Idea:
Have the class meet outside at night at least once during the first week or two of the term. A
flashlight with a fairly well focused beam makes a good pointer when working outside as long as the
humidity is not too low. The location of the north celestial pole, zenith, celestial equator, and ecliptic can be
adequately pointed out with a flashlight even to groups of more than 100. Some constellations, asterisms
and selected bright stars can also be presented. Working outside also helps students begin to notice the
natural world above them. It makes astronomy personal and something beyond the books, pictures, and
classroom.
TheSky Idea:
The primary function of The Sky software is to serve as a planetarium on your computer. There are
many demonstrations you can do or have your students do as lab experiments to illustrate concepts from this
chapter.
Set the program up for your current location, date and time. Make sure that you are in Daytime Sky
Mode and facing the northern horizon. Set the Time Step to 5 minutes. Under the View Tab select Filters
and set the magnitude limit to -30.0 to 5.0 and turn off the display of all objects except stars, planets, moon,
and sun. For now turn off all reference lines, including the constellation reference lines. Now you’re ready
to begin the demonstration. Press Alt+> and the program will display the daily motion of the sky in 5 minute
increments. At the 5-minute time step, a full 24 hours passes in about 35 seconds. Point out the circumpolar
stars and the general counterclockwise motion of the stars about the north celestial pole. Now click on the
icon in the tool bar to display the constellation lines. This will show where the constellations are during the
daylight hours as well, while still showing the blue sky of day. Next click on the tool bar icon to view the
eastern horizon. You can observe the general motion of objects as they rise at your location. Do this also
looking at the South and West horizons.
You can also demonstrate the effects of latitude on the apparent motion of the night sky with The
Sky. Perform The Sky Idea described above. Then alter your location to a new latitude. Go to the equator
or North Pole and run the demonstration again. Point out the difference in the size of the circumpolar region
and the angle at which objects climb above the eastern horizon and dive into the western horizon.
11
Chapter 2
RESOURCE INTEGRATION
Class Preparation/
Lecture Tools
Multimedia Manager Instructor’s Resource
CD-ROM
Customizable lecture tool with images,
animations, and video.
JoinIn™ on TurningPoint®
Book-specific student response system.
Great Ideas for Teaching Astronomy
Chapter 2 Science and Pseudoscience
Chapter 3 Observational and Historical
Astronomy
Transparency Package
Acetates 7–21
WebTutor™ ToolBox on WebCT and
Blackboard
http://webtutor.thomsonlearning.com
Free online course management option.
Book Companion Website
www.thomsonedu.com/astronomy/seeds Online
instructional resources and study tools
Student Mastery:
Homework/Tutorials/Labs
AceAstronomy
www.thomsonedu.com/astronomy/seeds Select
Chapter 2.
Active Figures
 Constellations from Different Latitudes
 The Celestial Sphere
 Rotation of the Sky
Introductory Astronomy Exercises
Exercise 2 Constellations and the Celestial
Sphere
TheSky™ Student Edition CD-ROM/
Workbook
Chapter 4 Naming Objects in TheSky
Chapter 5 Locating Objects in TheSky
Chapter 6 Motions in TheSky
Chapter 7 Keeping Time in TheSky
Chapter 8 Seasons in TheSky
Chapter 9 Phases and Eclipse in TheSky
RedShift™ College Edition CD-ROM/
Workbook
Chapter 3 Finding Your Way Around (in the
Dark!)
Chapter 4 Address UnKnown
Chapter 5 Timing is Everything
Out of the Classroom: Observations and
Investigations in Astronomy
Exercise 1 Using a Planisphere
Exercise 2 Altitude and Azimuth
Exercise 3 Apparent Magnitudes of Stars
Exercise 4 The Number of Stars Visible to the
Naked Eye
Exercise 8 Exploring the Winter Sky
Exercise 9 Exploring the Spring Sky
Exercise 10 Exploring the Summer Sky
Exercise 11 Exploring the Autumn Sky
12
Chapter 2
Full file at http://testbank360.eu/solution-manual-horizons-10th-edition-seeds
EDUCATIONAL RESOURCES
 Videos and Films
The Sky, 1994, (28 minutes) Produced by Coast Telecourse. Part of the Universe: The Infinite Frontier video
series. This program describes how the motions of Earth determine the length of the day and year and
the cause of the seasons. Additionally, it describes how different cultures viewed the sky.
Cycles of the Sky, 1994 (28 minutes) Produced by Coast Telecourse. Part of Universe: The Infinite Frontier.
This video describes the phases of the moon and eclipses.
Computer Software and CD-ROMs
There are several planetarium programs that simulate the night sky. These include RedShift College Edition
and TheSky Student Edition.
A few internet sites related to this material:
http://skytonight.com/
http://domeofthesky.com/
http://aa.usno.navy.mil/data/docs/RS_OneDay.html
http://www.space.com/spacewatch/
http://www.nightskyinfo.com/
http://nightsky.jpl.nasa.gov/planner.cfm
Lists events in the night sky
Online night sky with constellations
Sun and moon location data
Current observational events
Night sky events for the week
Planning tools for night sky
observations.
ANSWERS TO REVIEW QUESTIONS
1.
Most of the constellations that were not handed down from ancient civilizations were added during the
15th to 17th centuries. Some of the added constellations were very small constellations composed of
faint stars located in the Northern Hemisphere. These constellations filled in gaps between larger and
brighter constellations. Also added were constellations in the Southern Hemisphere that had not been
observed by western civilization. When sailors and explores began to sail south of the tropics, new star
patterns were observed and named to help in remembering them for navigation.
2.
An asterism is a group of stars that is not formally recognized as a constellation by the International
Astronomical Union (IAU). Many asterisms are part of larger constellations. There are 88
constellations officially recognized by the IAU. Examples of asterisms include the Big Dipper (part of
Ursa Major), the Great Square (part of Pegasus), the Water Jug (part of Aquarius), the Summer Triangle
(composed of three bright stars in the constellations of Lyra, Cygnus, and Aquilla), Medusa's Head (part
of Perseus.
3.
The stars in a constellation or an asterism are generally close to each other in the sky and have a shape
that suggests a particular object, person, or animal to the people of a given culture.
4.
People from different cultures all see the same stars, but the asterisms and constellations are different.
Technically, we would now all see the same constellations, because these have official definitions and
borders; however, this designation might not be well accepted by people of various cultures. The
asterisms are certainly dependent on the culture. The images we see in the sky depend on how we view
different objects and the value we place on them. Even within a culture we can have different asterisms.
My son sees a small duck in the sky. I have had him point it out in the planetarium, and see only a loose
collection of faint stars, but year after year he points out the same group of stars as a duck, so something
definitely appears as a duck to him.
13
Chapter 2
5.
The Greek letter designations generally indicate the brightnesses because the stars in a given
constellation were given Greek letter designations running in alphabetical order from brightest to
faintest within that constellation. This system does not allow us to compare the relative brightnesses of
stars in different constellations with certainty since the brightest star in each constellation is generally
designated , but not all constellations contain a really bright star.
6.
The magnitude system is sometimes said to be backwards because the brightest stars have the smallest
magnitudes. The reverse order of the system comes about from placing the stars in order of brightness.
The brightest stars were placed in the first group, magnitude 1, the next brightest stars were placed in the
second group, magnitude 2 and so on. Consequently, bright stars have small numerical magnitude
values, while faint stars have very large numerical magnitude values. This seems backwards because a
5th magnitude star is fainter than a 1st magnitude star.
7.
The word apparent in apparent visual magnitude means simply that it is the magnitude of the star as it
appears to us when viewing the star from here on Earth. Apparent visual magnitude does not take into
account any corrections for the star's distance or size or temperature or the amount of dust between us
and the star. It is simply the brightness as it appears to us in the night sky.
8.
The celestial sphere is an excellent scientific model. It is an accurate representation of what we observe
when we view the night sky. Note that as we look out at the night sky, all the stars appear to be an equal
distance away as if they were dots painted on a giant ceiling. Consequently, the celestial sphere does
represent what we see, and permits us to discuss what would happen if Earth is at the center and Earth
rotated on its axis, and/or revolved around the sun. It provides us with a way to step back and picture in
our minds what is going on as Earth rotates on its axis and revolves around the sun.
9.
The use of the word on instead of the word in when referring to angular distance between celestial
objects comes about because all of the objects appear to be on the celestial sphere and at an
indeterminable distance. While we know that objects are at different distances in the sky, their distance
from Earth is irrelevant in determining the angular distance between the two objects as viewed from
Earth.
10. The celestial poles and celestial equator exist because Earth rotates on an axis. If Earth did not rotate we
could define the ecliptic and the poles of the ecliptic, but there would not be a separate set of celestial
poles and celestial equator. Under such a circumstance, we would have difficulty defining a geographic
equator and geographic poles. The geographic equator would most likely be defined as the intersection
between the ecliptic and Earth's surface and the geographic poles would be 90° from this equator.
11. To see the north and south celestial poles at the same time, one needs to be at Earth's equator. Due to
the refraction of light by the atmosphere, an observer on the equator would observe the north celestial
pole approximately 0.5° above the northern horizon and the south celestial pole about 0.5° above the
southern horizon. An observer at latitudes between 0.5° S and 0.5° N could see both celestial poles
above their horizon.
12. A celestial pole will be on your zenith if you are at a latitude of 90° N, the north geographic pole, or at
90° S, the south geographic pole.
13. Your latitude can be determined by observing the angle between your northern horizon and the north
celestial pole. Since Polaris, the North Star, is within 1° of the north celestial pole, Polaris can be used
as a fairly accurate marker of the north celestial pole. Determining latitudes in the southern hemisphere
is more difficult because there is no bright star within a few degrees of the south celestial pole.
14. Circumpolar constellations are those constellations close enough to the celestial pole so that they never
pass below an observer's horizon, but instead pass directly between the observer's celestial pole and
northern or southern horizon at their lowest points in the sky. At different latitudes the celestial pole
will be at different distance above an observer's horizon. If the observer is at a latitude of 60° N, then all
constellations within 60° of the north celestial pole will be circumpolar. However, if an observer is at a
14
Chapter 2
Full file at http://testbank360.eu/solution-manual-horizons-10th-edition-seeds
latitude of only 30° N, then only those constellations within 30° of the north celestial pole will be
circumpolar.
15. One of the easiest ways to detect the existence of precession by examining ancient Egyptian star charts
would be to look at which stars they show as circumpolar and which are circumpolar in Egypt now.
Since the location of the north celestial pole moves relative to the stars because of precession, the stars
that appear within the circumpolar zone also changes. If on the ancient charts, Thuban is listed as
"nearest the pole", then at the latitude of approximately 30° N, Polaris would have been circumpolar, but
would have been very near the horizon at its lowest point. Additionally, all of the Big Dipper asterism
would have been circumpolar, while today only one of the seven bright stars forming the Big Dipper is
circumpolar at Egypt's latitude.
16. It appears to be upside down compared to the way northern hemisphere observers are used to seeing the
constellation.
ANSWERS TO PROBLEMS
1.
2.
3.
4.
5.
4
2800
Star A is the brightest, Stars A and B are visible to the unaided eye, Star A is 16 times brighter than Star
B.
The sun is about 1,000,000(1 million) times brighter than the full moon.
Angle from northern horizon to north celestial pole is 35°; Angle from southern horizon to south
celestial pole is 35°.
ANSWERS TO BUILDING SCIENTIFIC ARGUMENTS
1.
Astronomers continue to use the magnitude system after two millennia because we can compare the
magnitude of a star today with the magnitude determined many years ago. There now exists a large
body of information in terms of magnitudes, so it is easiest if we continue the system. Additionally, like
many things that seem confusing or awkward at first, it becomes easy to use once you have learned to
use it.
2.
A more exact definition of circumpolar constellations would be; a constellation that is located entirely
within an angular distance of a celestial pole that is equal to the observer's latitude. With this definition
of a circumpolar constellation, Ursa Major would not be a circumpolar constellation for any observer
south of about 58°N latitude since some of the stars of Ursa Major extend roughly 58° (Alula Australis)
from the north celestial pole. Orion would not be a circumpolar constellation for any observer because a
portion of Orion is more than 90° away from the north celestial pole, and another portion of Orion is
more than 90° away from the south celestial pole. With this definition, any constellation that extends
across the celestial equator, as Orion does, could not be a circumpolar constellation for any observer.
TEST QUESTIONS
Multiple Choice Questions
1.
*
Seen from the northern latitudes, the star Polaris
a. is never above the horizon during the day.
b. always sets directly in the west.
c. is always above the northern horizon.
d. is never visible during the winter.
e. is the brightest star in the sky.
15
Chapter 2
2.
*
3.
*
4.
*
An observer on Earth's equator would find
a. Polaris directly overhead.
b. Polaris 40° above the northern horizon.
c. that the celestial equator coincides with the horizon.
d. that the celestial equator passing directly overhead.
e. that the ecliptic coincides with the horizon.
The celestial equator is
a. a line around the sky directly above Earth's equator.
b. the dividing line between the north and south celestial hemispheres.
c. the path that the sun appears to follow on the celestial sphere as Earth orbits the sun.
d. a and b.
e. a and c.
The ________ is the point on the celestial sphere directly above any observer.
a. north celestial pole
b. south celestial pole
c. zenith
d. celestial equator
e. asterism
5.
*
Constellation names are in
a. Latin.
b. Greek.
c. Arabic.
d. English.
e. Italian.
6.
Most star names, such as Aldebaran and Betelgeuse are
a. Latin.
b. Greek.
c. Arabic.
d. English.
e. Italian.
*
7.
*
8.
*
9.
*
The magnitude scale
a. originated just after the telescope was invented.
b. can be used to indicate the apparent intensity of a celestial object.
c. was devised by Galileo.
d. is no longer used today.
e. was used to determine the rate of precession.
The apparent visual magnitude of a star is a measure of the star's
a. size.
b. intensity.
c. distance.
d. color.
e. temperature.
The apparent visual magnitude of a star is 7.3. This tells us that the star is
a. one of the brighter stars in the sky.
b. bright enough that it would be visible even during the day.
c. not visible with the unaided eye.
d. very far from Earth.
e. very close to Earth.
16
Chapter 2
Full file at http://testbank360.eu/solution-manual-horizons-10th-edition-seeds
10. The star Vega has an apparent visual magnitude of 0.03 and the star HR 4374 has an apparent visual
magnitude of 4.87. It has been determined that both stars are at the same distance from Earth. What
does this information tell us about the two stars?
a. Vega must be closer to Earth than HR 4374.
b. Vega must be farther from Earth than HR 4374.
c. Vega must produce less energy than HR 4374.
* d. Vega must produce more energy than HR 4374.
e. Vega will appear fainter to us than HR 4374.
11. The _______________ of an object depends on the diameter of the object and the distance to the object.
a. apparent brightness
b. apparent magnitude
c. zenith
* d. apparent diameter
e. apparent distance
12. An observer’s nadir is
* a. the point directly opposite the observer’s zenith.
b. the north point on the observer’s horizon.
c. located at the center of Earth.
d. always located near a circumpolar constellation.
e. directly opposite the north celestial pole.
13. A(n) __________________ is one-3,600th of a degree.
a. precession
* b. second of arc
c. minute of arc
d. nadir
e. angular diameter
14. The Big Dipper is
a. a circumpolar constellation for southern hemisphere observers.
b. always on an observer’s zenith.
* c. an asterism.
d. only visible from the southern hemisphere.
e. a constellation.
15. Precession of the rotation axis of Earth is caused by
* a. the force of gravity from the sun and moon on Earth's equatorial bulge.
b. the force of gravity from the sun and Jupiter on the Earth-moon system.
c. the magnetic field of Earth.
d. the formation and subsequent melting of glaciers during the ice-ages.
e. the impact of asteroids.
16. An observer in the Northern Hemisphere watches the sky for several hours. Due to the motion of Earth,
this observer notices that the stars near the north celestial pole appear to move
* a. counter clockwise around the celestial pole.
b. clockwise around the celestial pole.
c. from left to right.
d. from right to left.
e. nearly vertically upward.
17
Chapter 2
17. You live at a latitude of 73° N. What is the angle between the northern horizon and the north celestial
pole?
* a. 73°
b. 27°
c. 17°
d. 23½°
e. 5°
18. You live at a latitude of 39° S. What is the angle between the southern horizon and the south celestial
pole?
a. 45°
b. 23.5°
* c. 39°
d. 51°
e) The answer depends on the day of the year.
19. You live at a latitude of 28° N. What is the angle between the northern horizon and the north celestial
pole?
a. 62°
* b. 28°
c. 40°
d. 23½°
e. 5°
20. You live at a latitude of 16° S. What is the angle between the southern horizon and the south celestial
pole?
a. 74°
b. 164°
* c. 16°
d. 23½°
e. 5°
21. You live at a latitude of 39° S. What is the angle between the southern horizon and the south celestial
pole?
a. 45°
b. 23.5°
* c. 39°
d. 51°
e) The answer depends on the day of the year.
22. If the north celestial pole appears on your horizon, what is your latitude?
a. 90° N
b. 90° S
* c. 0°
d. 45° N
e. The latitude of the observer can not be determined from the information given.
23. What is the approximate latitude of the observer in the diagram to the right?
a. 90° N
b. 90° S
* c. 50° N
d. 50° S
e. 0°
18
North
Celestial
Pole
E
N
S
W
Chapter 2
Full file at http://testbank360.eu/solution-manual-horizons-10th-edition-seeds
24. What is the approximate latitude of the observer in the diagram to the
right?
a. 20° N
* b. 20° S
c. 70° N
d. 70° S
e. 0°
25. An observer in the Northern Hemisphere takes a time
exposure photograph of the night sky. If the illustration to the
right depicts the photograph taken by the observer, which
direction was the camera pointing?
a. straight north
b. straight east
* c. straight south
d. straight west
e. straight up, directly overhead
26. An observer in the Northern Hemisphere takes a time
exposure photograph of the night sky. If the illustration to the
right depicts the photograph taken by the observer, which
direction was the camera pointing?
a. straight north
b. straight east
c. straight south
* d. straight west
e. straight up, directly overhead
27. An observer in the Southern Hemisphere takes a time
exposure photograph of the night sky. If the illustration to the
right depicts the photograph taken by the observer, which
direction was the camera pointing?
a. straight north
b. straight east
* c. straight south
d. straight west
e. straight up, directly overhead
28. An observer in the Southern Hemisphere takes a time
exposure photograph of the night sky. If the illustration to the
right depicts the photograph taken by the observer, which
direction was the camera pointing?
a. straight north
* b. straight east
c. straight south
d. straight west
e. straight up, directly overhead
19
E
N
South
Celestial
Pole
S
W
Star Trails
Horizon
Star Trails
Horizon
Star Trails
Horizon
Star Trails
Horizon
Chapter 2
29. An observer in the Northern Hemisphere takes a time
exposure photograph of the night sky. If the illustration to the
right depicts the photograph taken by the observer, which
direction was the camera pointing?
* a. straight north
b. straight east
c. straight south
d. straight west
e. straight up, directly overhead
Star Trails
Horizon
30. An observer in the Southern Hemisphere takes a time
exposure photograph of the night sky. If the illustration to the
right depicts the photograph taken by the observer, which
direction was the camera pointing?
a. straight north
b. straight east
c. straight south
* d. straight west
e. straight up, directly overhead
31. Which star in the table to the right would appear the
brightest to an observer on Earth?
a.  Cet
* b.  CMa
c. Nim
d.  Per
e.  Dra
32. Based on the information in the table to the right, what
is the ratio of the intensity of  Dra to that of Nim?
a. 2.512
b. 5
c. 8.07
d. 11.14
* e. 100
33. Which star in the table to the right would not be visible
to the unaided eye of an observer on Earth?
a.  Cet
b.  Cma
* c. Nim
d.  Per
e.  Dra
20
Star Trails
Horizon
Star
Name
 Dra
 Cet
 Per
Nim
 Cma
Star
Name
 Dra
 Cet
 Per
Nim
 Cma
Star
Name
 Dra
 Cet
 Per
Nim
 Cma
Apparent Visual
Magnitude
3.07
2.53
3.98
8.07
-1.46
Apparent Visual
Magnitude
3.07
2.53
3.98
8.07
-1.46
Apparent Visual
Magnitude
3.07
2.53
3.98
8.07
-1.46
Chapter 2
Full file at http://testbank360.eu/solution-manual-horizons-10th-edition-seeds
34. Star A has an apparent visual magnitude of 13.4 and star B has an apparent visual magnitude of 15.4.
Star A is _________________ than star B.
a. 2 times fainter
b. 2 times brighter
c. 6.3 times fainter
* d. 6.3 times brighter
e. 29.8 times fainter
35. Polaris is a second magnitude star, and Phi Pegasi is about 16 times fainter than Polaris. What is the
approximate magnitude of Phi Pegasi?
a. 18
b. -14
c. 3
d. -3
* e. 5
36. Do the appearance of the constellations follow a seasonal pattern?
a. No, all of the constellations are on any clear night of the year.
b. Yes. As the year progresses, the constellations move to different areas of the sky.
c. Yes, during a winter night all the constellations you can see are different from the ones that appear
during a summer night.
* d. Yes, during a summer night many of the constellations you can see are different from those you can
see on a winter night. However, there are some constellations that are visible all year long.
37. Which of the following statements correctly describes the relationship between stars and constellations?
a. Only stars close to the ecliptic (the Earth's orbital plane) are located in constellations.
* b. Every star is located in a constellation.
c. Only the brighter stars are in constellations.
d. Only those stars that were visible to the ancient Greeks are located in constellations.
38. How much of the night sky is north of the celestial equator?
a. Less than one-half, because of the tilt of the equator to the ecliptic plane.
b. More than one-half, because of the precession of the poles.
* c. Exactly one-half.
d. All of the night sky.
39. If you point toward the zenith right now and then point there again 6 hours later, you will have pointed
twice in the same direction relative to
* a. your horizon.
b. the Sun.
c. the Moon.
d. the fixed stars.
40. If an observer walks north toward increasing latitude, the number of circumpolar stars would
a. remain constant.
b. decrease.
* c. increase.
d. Unknown unless you also state the longitude of the observer.
41. If you were standing on the Earth’s equator, which of the following point in the sky would pass through
your zenith at some time during one full day (24 hours)?
a. The north celestial pole
b. The summer solstice
* c. The vernal equinox
d. The ecliptic pole
21
Chapter 2
42. If the Sun passes directly overhead on at least one day per year, then
* a. you are within 23½° latitude of the equator.
b. you are within 66½° latitude of the equator.
c. you must be exactly on the equator.
d. you could be anywhere because this occurs at least once per year at any location on the Earth.
43. In Brazil, the longest period of daylight occurs during the month of
* a. December.
b. March.
c. September.
d. June.
44. If you are standing at the Earth’s North Pole, which of the following would be located at the zenith?
a. The nadir
b. The star Vega
c. The celestial equator
* d. The north celestial pole
45. For stars the same constellation they
a. probably formed at the same time.
b. must be part of the same cluster of stars in space.
c. must have been discovered at about the same time.
* d. may actually be very far away from each other.
46. During the month of June the north celestial pole points towards Polaris but during the month of
December it points
a. just north of Polaris.
b. just south of Polaris.
c. towards the star Vega.
d. towards the star Thuban.
* e. still towards Polaris.
47. If the Earth’s period of rotation doubled, but the period of revolution stayed the same
a. the night would be twice as long.
* b. the night would be half as long.
c. the year would be half as long.
d. the year would be twice as long.
e. the length of the day would be unchanged.
Fill in the Blank Questions
1.
__________ is a measure of the light energy that hits one square meter in one second.
** Intensity
2.
The ________ is the point on the celestial sphere directly above an observer, regardless of where the
observer is located on Earth.
** Zenith
3.
Star A has an apparent visual magnitude of 6.3 and star B has an apparent visual magnitude of 5.3. Star
A is _________ times ________ than star B.
** 2.5
fainter
22
Chapter 2
Full file at http://testbank360.eu/solution-manual-horizons-10th-edition-seeds
4.
Earth's rotation axis _______________ slowly so that in a few thousand years Polaris will no longer be
the North Star.
** precesses
5.
The full moon has an angular diameter of approximately _______ arc minutes for an observer located on
the surface of Earth.
** 30
True-False Questions
F
1.
The constellations were created by the Greeks.
T
2.
A second magnitude star in Ursa Major is brighter than a fourth magnitude star in Orion.
T
3.
The Greek letter designation conveys information about a star's location and brightness.
F
4.
The celestial equator always passes directly overhead.
T
5.
The celestial equator always crosses the horizon at the east point and west point.
T
6.
Navigators can find their latitude in the northern hemisphere by measuring the angle from the
northern horizon to the north celestial pole.
T
7.
A scientific model is a mental conception that provides a framework that helps us think about some
aspect of nature.
F
8.
The constellation of Orion is currently visible in the evenings in January. Precession will not affect
this and Orion will still be visible in January 13,000 years from now.
F
9.
A 3rd magnitude star is 3 times brighter than a 1st magnitude star.
T
10. As Earth rotates, circumpolar stars appear to move counterclockwise around the north celestial pole.
Essay Questions
1.
Describe the path that a star on the celestial equator follows from the time it rises until it sets for a
person at a latitude of 60° N and a person at the equator.
2.
Describe the location of Polaris in the sky relative to the horizon as seen by observers in Alaska (lat. =
60° N), Texas (lat. = 33° N), Ecuador (lat. = 0°), and Australia (lat. = 30° S)
3.
What information does a star's Greek-letter designation convey?
4.
What advantage is there in referring to a star by its Greek-letter designation and constellation name
rather using its traditional name?
5.
How are the celestial poles and equator defined by Earth's rotation?
6.
How is a constellation different from an asterism?
RECOMMENDED READING
Allen, Richard Hinckley Star Names: Their Lore and Meaning, New York: Dover, 1963.
23
Chapter 2
Aveni, Anthony "A Stairway to the Stars." Astronomy 25 (Nov. 1997), p. 92.
Condos, Theony Star Myths of the Greeks and Romans: A Sourcebook, Grand Rapids, MI, Phanes Press,
1997.
Gurshtein, Alexander A. "In Search of the First Constellations." Sky and Telescope 93 (June 1997), p. 46.
Haynes, Roslynn "Looking Back Cosmologically." Sky and Telescope 94 (Sept. 1997), p. 72.
Kunitzch, Paul "How We Got Our 'Arabic' Star Names." Sky and Telescope 65 (Jan. 1983), p. 20.
Levy, David H. "Ten Dark-Sky Years." Sky and Telescope 96 (Sept. 1998), p. 32.
MacRobert, Alan M. "Backyard Astronomy: Dissecting Light Pollution." Sky and Telescope 92 (Nov.
1996), p. 44.
Pasachoff, Jay M. and Wil Tirion A Field Guide to the Stars and Planets. Boston: Houghton Mifflin, 2000.
Monroe, Jean Guard, and Ray A. Williamson They Dance in the Sky: Native American Sky Myths. Boston:
Houghton Mifflin, 1987.
Norton, A.P. A Star Atlas. Cambridge, Mass.: Sky Publishing, 1964.
Rao, Joe "The Return of the Leonid Meteors." Sky and Telescope 96 (Nov. 1998), p. 38.
Staal, Julius, D.W. The New Patterns in the Sky: Myths and Legends of the Stars. Blacksburg, VA:
McDonald and Woodward Publishing, 1988.
Schaefer, Bradley E. “The Origin of the Greek Constellations.” Scientific American 295 (Nov. 2006), p. 96.
Serviss, Garret P. Astronomy with the Naked Eye - A New Geography of the Heavens. Standard Publications,
Incorporated, 2006.
Whitney, Charles A. Whitney's Star Finder. New York: Alfred A. Knopf, 1980.
Williamson, Ray A. Living the Sky: The Cosmos of the American Indian. Boston: Houghton Mifflin, 1984.
24
Chapter 2