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SCI-103 Introductory Astronomy Exam #1 Spring 2012
Name_____________________
Class Meeting Time_____________
Grade Summary
HW #1_____________ (out of 20 points)
HW #2_____________(out of 20 points)
Exam #1 ___________ (58 points total)
Grade So Far _______
This is a pretty meaningless measure of your performance in the course as a
whole given that we were only 2 weeks into the course, but it does say
something as to your success in learning the new material.
Answer the following Multiple Choice Questions by circling the correct response. (1 or 2 (the last
four questions) points each for a total of 23 points)
1) Imagine that you are visiting Antarctica on a cruise to see penguins. You step outside at night and
look at the stars. Where would you look to see the South Celestial
Pole?
A) North, near the horizon (0 altitude)
B) Near the zenith (90altitude)
C) North, near 43 altitude
D) Northwest, in the direction towards the U.S.A.
E) The SCP cannot be seen from this location.
2) During Spring Break you and your friends plan to travel south to Cancun, Mexico for a week of sun
and fun. You arrive in Cancun on a clear night. You look up at the stars and notice that they appear
different that the stars you see in Syracuse, NY. Which of the statements below is true regarding the
appearance of the stars in Cancun? Circle all that are true.
A) Polaris will appear higher in the sky than as seen in Syracuse.
B) The circumpolar region will appear smaller compared to its size in Syracuse.
C) Stars will complete one cycle in the same time as seen in Syracuse.
D) You can see stars in the southern sky that are not visible from Syracuse.
3) The long exposure image of star trails shown
below was taken while looking toward the east.
From which of the locations listed below was the
image obtained?
A) Sydney, Australia (Latitude 34 S)
B) Lima, Peru (Latitude 12 S)
C) Quito, Equador (Latitude 0 N)
D) Canary Islands (Latitude 29 N)
E) Berlin, Germany (Latitude 52 N)
The Slant to the South tells you its a
Northern latitude.
Slant Angle = Obs. Lat
This is angle is less than 45 degrees.
EASTERN HORIZON
4) Which of the following locations is closest to the
north celestial pole?
A) RA = 14 h
dec = -85
B) RA = 0 h
dec = -43
C) RA = 23 h
dec = +43
D) RA = 14 h
E) RA = 8 h
dec = +85
dec = -2
5) Which of the following coordinates in your local horizon system (in Syracuse, NY at 43 N) is closest to
the zenith?
A) Az. = 180, Al. =43
D) Az. = 35,
Al. = 2
B) Az. = 273, Al. =52
E) Az. = 3,
Al. = 48
C) Az. = 90,
Al. = 90
6) Imagine that you are observing the stars at an observatory located outside El Paso, Texas (latitude =
32N). You may find the diagram below helpful.
CE, 0° dec
NCP, 90° dec
32°
Southernmost visible star
0°-58° = -58° dec
S
58°
58°
32°
N
Boundary of Circumpolar
Region 90°-32° = 58° dec
A) At what altitude would Polaris appear above the northern horizon?
Polaris would appear 32 degrees above the northern horizon (Dr.
Fred’s Rule #1)
B) Would a star with a declination of +60 be circumpolar? Explain.
A star with a declination of +60° would be 2° inside the circumpolar
boundary and would thus be circumpolar. (Dr. Fred’s Rule #2)
C) What would be altitude of the Celestial Equator looking south?
The altitude of the celestial equator would be 58° above the southern
horizon. (Read from the diagram above)
D) Would you be able to observe stars as far south as -50 declination? Explain.
The southernmost visible star has a declination of -58°. A star at -50° would be 8°
north of that star and would briefly be visible above the southern horizon. (Dr.
Fred’s Rule #4)
E) Where would the celestial equator intersect the horizon?
The celestial equator intersects the horizon exactly due east and due west for all
observers. (Dr. Fred’s Rule #3)
Questions 7 and 8 below address the apparent motion of the stars as seen by an observer in El Paso,
Texas. A map of the United States below indicates the location of this city.
Syracuse, NY
El Paso, TX
7) If a particular star passed through the meridian in Syracuse, NY, how many hours before that same
star crossed the meridian in El Paso TX (see map at the beginning of the problem)?
A) 1 hr
C) 3 hr
E) 5 hr
D) 4 hr
B) 2 hr
8) In each of the boxes below, sketch carefully the apparent motion of the stars as seen in El Paso Texas
looking north, east and south. Include all quantitative information and timescales regarding the apparent
motions. Use the margins to record any notes regarding the apparent motions you think are relevant.
Boundary of the circumpolar region is
58 declination
60
Stars are above
the horizon for
more than 12
hours looking
North.
Stars circle counter
clockwise around the NCP
every 23 h 56 m
50
40
Polaris (NCP really)
Azimuth=0 (due North)
Altitude = 32
Altitude
30
20
10
Apparent Motion of the Stars Looking North
Celestial Equator
intersects the horizon due
East (and West) for all
observers
Stars are above
the horizon for
about12 hours
looking East.
Slant Angle =
32 relative to
the vertical
32
32
32
32
Apparent Motion of the Stars Looking East
Stars are above
the horizon for
less than12
hours looking
South.
The SCP is below the
horizon
Apparent Motion of the Stars Looking South
Name__________________________________
1) The concept of the celestial sphere is ancient appearing in the oldest records of astronomical writings. In
spite of its ancient beginnings, the celestial sphere concept is still taught today as a core component in
celestial navigation classes for mariners and pilots. In a brief essay (10 to 20 sentences), describe the
celestial sphere. Include its “geography”, its relation to the Earth’s geography, its apparent motion and any
quantitative information pertaining to the apparent motion of the celestial sphere.
Use this page to construct the outline of your response. Take a few minutes to jot down some points regarding
the essay topic that will help you organize your final essay. Write your final essay on the next page. Additional
blank pages are available if needed.
Points to include in the essay:
 The celestial sphere is a conceptual model not a real physical model of the heavens.
 The Earth is located at the center of the celestial sphere.
 “Geography” of the celestial sphere
o North Celestial pole and South Celestial pole are two fixed points on the celestial
sphere.
o Celestial Equator divides the celestial sphere into northern and southern
hemispheres.
o The celestial sphere can be gridded into latitude and longitude like celestial
coordinates called Right Ascension and Declination.
 Relation to Earth’s geography
o The NCP and SCP are directly above the Earth’s north geographic pole and south
geographic pole.
o The celestial equator is directly above the Earth’s equator.
o The declination of the zenith for any observer equals the observer’s latitude.
 Apparent Motion of the celestial sphere
o The celestial sphere appears to rotate westward once every 23 h 56 m 4.09 s.
o To an observer in the Earth’s northern hemisphere:
 Looking North - the stars appear to move ccw around Polaris (NCP really).
Some of the stars are circumpolar looking north.
 Looking East - stars rise along slanted paths toward the south, slant angle
equals the observer’s latitude.
 Looking South – Stars appear to move on downward curving arcs centered
on the SCP that is hidden below the horizon.
 Looking West - stars set along slanted paths from the south, slant angle
equals the observer’s latitude.
The Celestial Sphere
Name__________________________
Solve the following problems showing your work. (4 points each for a total of 12 points)
1) The Earth is quite small and far from the Sun. Calculate how many Earth’s could fit side-by-side between
the Sun’s center and the orbit of the Earth.
Use a ratio of the distance to the Sun over the diameter of the Earth
Distance to Sun
1 AU
150 106 km


 11,759
Diameter of Earth 2  6,378 km 2  6,378 km
Almost 12,000 Earth’s would fit in the distance between the Sun’s center and the Earth’s orbit.
2) If the Earth were scaled down to a sphere 1 foot in diameter, what would be the distance to Proxima
Centauri, the nearest star beyond the Sun that is actually 4.3 ly away?
Use a proportion to solve this scale problem.
Model Distance to Proxima Centauri Actual Distance to Proxima Centauri

Model Diameter of Earth
Actual Diameter of Earth
x
4.3 ly

1 ft 2  6,378 km
x
4.3  9.46 1015 m

1 ft
2  6.378 106 m
4.3  9.46 1015
x
1 ft
2  6.378 106
x  3.19 109 ft
x  603,964 miles
Proxima Centauri would be 3.19 billion feet or about 604,000 miles away from the 1 foot diameter Earth. This
distance is over twice the actual distance to the Moon.
3) If astronauts were to travel to the center of the Milky Way galaxy using a spacecraft that travelled at
commercial airliner speeds (1,000 km/hour or 278 m/s), how much time would be required to make the
journey? The distance from the Earth to the center of the Milky Way is 28,000 ly. Express your answer in
seconds and in years.
d
problem.
v
d 28,000 ly 28,000  9.46 1015 m
t 

 9.52 1017 s  3.02 1010 yr  30 Billion years
m
m
v
278
278
s
s
This is a t 
The journey would take 9.521017 seconds or about 30 billion years. Note that the Universe is believed to be
only 13 billion years old. So the trip would take three times longer than the Universe is old.
Astronomy Formula and Constants Sheet for Exams
Conversions
Formulas
A
L

2D
360 
Main Sequence Lifetime t 
M
1010 yr
L