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Astronomer:
Astronomy 12 Unit Test Review
Charting the Sky
Part I- Multiple choice: Answer each question by shading the most appropriate bubble.
01. Astronomy is the study of
a. the stars and planets and their movements as well as their affects on the lives and behavior
of human beings.
b. the weather and of atmospheric processes.
c. the structure and evolution of the earth's crust.
d. everything in the universe that lies above Earth's atmosphere.
02. Which of the following terms would not be associated with astronomy?
a. horoscope b. telescope c. spectroscope d. celestial sphere
03. A planet is an object which
a. occurs only in our solar system. b. is too faint to see.
c. orbits a star. d. does not generate its own energy from nuclear reactions
04. In astronomical terms, one brief description of a star is
a. a small point of light seen only at night.
b. a radiant body at least 3 million times as massive as the Earth.
c. a bright object with a five-pointed shape.
d. a body which shines from its own internal source of energy.
05. A galaxy is
a. a large cloud of gas.
b. an exploding star.
c. the object from which all other objects in the universe were formed.
d. a collection of a large number of stars bound by gravity.
06. A(n) _____ is the totality of all space, time, matter, and energy.
a. universe b. galaxy c. planet d. star
07. Which of the following is arranged from the smallest to the largest in size?
a. planet, star, universe, galaxy b. star, planet, galaxy, universe
c. planet, star, galaxy, universe d. universe, galaxy, star, planet
08. What are constellations?
a. galaxies of stars
b. configurations of bright stars patterned by humans
c. areas of the sky, each 15 x 15 degrees
d. physical groupings of stars all at the same distance from Earth
09. The picture below shows Orion’s Belt.
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Orion’s Belt
Orion’s Belt is an example of a(n)
a. constellation. b. asterism. c. star cluster. d. galaxy.
11. A band of the celestial sphere extending on either side of the ecliptic that represents the
path of the different celestial bodies (i.e. Moon, Sun, planets) and contains constellations like
Gemini and Aquarius is called the
a. North Celestial Pole. b. South Celestial Pole. c. Celestial Equator. d. Zodiac.
12. An imaginary sphere of infinite extent with Earth at its center on which the stars, planets,
and other heavenly bodies appear to be located is known as the
a. Zodiac. b. celestial sphere. c. atmosphere. d. lithosphere.
14. FILL IN THE BLANKS: Declination is analogous to geographical ______________. Right
ascension is analogous to geographical ______________.
a. latitude; longitude b. longitude; latitude c. north pole; south pole d. south pole; north pole
15. The time needed for a star on the celestial sphere to make one complete rotation in the
sky is referred to as a
a. sidereal month. b. solar year. c. sidereal day. d. solar day.
16. The period of time between the instant when the Sun is directly overhead to the next time
it is directly overhead is referred to as a
a. sidereal month. b. solar year. c. sidereal day. d. solar day.
17. Relative to the stars on the celestial sphere, over the course of a year, the ecliptic is the
apparent path of what celestial body?
a. Moon b. Sun c. Alpha Centauri d. Earth
18. The Sun rises in the east and sets in the west because
a. the Earth rotates on its axis. b. the Earth revolves around the Sun.
c. the Moon revolves around the Earth. d. the Earth ‘wobbles’ on its axis.
19. The point on the ecliptic where the Sun is at its northernmost point above the celestial
equator, occurring on or near June 21, is known as
a. winter solstice. b. vernal equinox. c. summer solstice. d. autumnal equinox.
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20. The point on the ecliptic where the Sun is at its southernmost point below the celestial
equator, occurring on or near December 21, is known as
a. winter solstice. b. vernal equinox. c. summer solstice. d. autumnal equinox.
21. The date on which the Sun crosses the celestial equator moving southward, occurring on
or near September 22 is known as
a. winter solstice. b. vernal equinox. c. summer solstice. d. autumnal equinox.
22. The date during which the Sun crosses the celestial equator, moving northward, occurring
on or near March 21.
a. winter solstice. b. vernal equinox. c. summer solstice. d. autumnal equinox.
23. The time required for the constellations to complete once cycle around the sky and return
to their starting points, as seen from a given point on Earth, is referred to as a
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a. synodic month. b. sidereal month. c. tropical year. d. sidereal year.
24. The time interval between one vernal equinox and the next is referred to as a
a. synodic month. b. sidereal month. c. tropical year. d. sidereal year.
25. The slow but relatively uniform motion of the earth's rotational axis that causes changes in
the coordinate systems used for mapping the sky is known as
a. rotation. b. parallax. c. precession. d. revolution.
26. The difference in position of a star as seen from the Earth at different locations around the
orbit of the Sun is known as
a. revolution. b. transit. c. stellar parallax. d. precession.
27. The appearance of the sunlit face of the Moon at different points along its orbit, as seen
from Earth, is referred to as a
a. parallax.
b. phase.
c. lunar eclipse.
d. solar eclipse.
28. A _____ eclipse occurs whenever the Moon passes through some portion of the Earth's
shadow.
a. solar
b. lunar
c. total
d. partial
29. A _____ eclipse occurs when the Moon passes between Earth and the Sun, thereby
obscuring Earth's view of the Sun.
a. solar
b. lunar
c. total
d. partial
30. The darkest part of the shadow is called the
a. penumbra.
b. umbra.
c. baseline.
d. dark zone.
31. The part of a shadow where the light source is only partially blocked is called the
a. penumbra.
b. umbra.
c. baseline.
d. light zone.
32. TRUE or FALSE. Moonlight is the emission of light from the Moon, produced at its core.
Answers: 1.d; 2.a; 3.c; 4.d; 5.d; 6.a; 7.c; 8.b; 9.b; 11.d; 12.b; 14.a; 15.c; 16.d; 17.b; 18.a; 19.c; 20.a; 21.d; 22.b;
23.d; 24.c; 25.c; 26.c; 27. b; 28. b; 29. a; 30. b; 31. a; 32. F
Part II- Short Answer: Answer each question on the test paper in the space provided.
33. Label the various parts of the celestial sphere below:
A ___________________________
B ___________________________
C ___________________________
D ___________________________
E ___________________________
A – celestial equator; B – ecliptic; C – north celestial pole; D – south celestial pole; E – Earth
34. The solar day is 3.9 minutes longer than the sidereal day. Why is this so?
The solar day is longer than the sidereal day because, since it is measured from successive positions of the
Sun in the sky or ‘noon times’, it accounts for not only the Earth’s rotation about its axis but also the small
change in its orbit around the Sun.
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35. Why does Earth experience seasons? Be sure to mention Earth’s rotational axis and the Sun’s energy in your answer.
The Earth experiences seasons because it is tilted on its axis. At summer solstice, the Earth is tilted towards the
Sun, causing solar rays to fall on the Earth’s atmosphere more directly. At this time of year, the Sun remains longer
in the sky. These two factors cause the temperature of the atmosphere to increase, leading to summer. At winter
solstice, the Earth is tilted away from the Sun, causing solar rays to fall on the Earth’s atmosphere less directly. At
this time of year, the Sun remains in the sky for shorter periods. These two factors cause the temperature of the
atmosphere to decrease, leading to winter.
36. The sidereal year is about 20 minutes longer than the tropical year.
a. Why is this so?
b. If modern calendars were based on the sidereal year, what would be the effect on timekeeping?
The sidereal year is longer than the tropical (solar) year because it is measured as the length of time it takes
Earth to revolve around the Sun, based on the position of fixed stars. Precession causes ‘fixed star’ position
to change slightly, leading to approximately 20 additional minutes to the year. If modern calendars used the
sidereal year for timekeeping, major events like Easter would fall at different times of the year.
37. Why are some stars seen throughout the year? What do we call these stars?
Some stars are seen throughout the year because they are high enough in the sky so that our horizon includes
them and they never set. These stars are considered circumpolar.
38. Describe a distance measuring scenario in which the following units would be appropriate: AU, light year and
kiloparsec.
AU is appropriate for solar system distances; light year and kiloparsec are appropriate for stellar and galactic
distances.
39. Describe three ways in which ancient civilizations used constellations.
astronomy; timekeeping/calendars; religious observances; oral traditions; navigation
40. Mars is 58 000 000 km from Earth. How long would it take a beam of light sent from Earth to reach Mars?
time = (distance)/(speed of light) = t = d/c = (58 000 000 km)/(3.0 x 105 km/s) = 193 seconds
41. The Hubble Space Telescope has a resolution of about 0.05 arc seconds. What is the smallest object it can see on the
surface of the Moon? Give your answer in kilometers and meters. Note: the distance from the Earth to the Moon is 384 000
km.
d
D
206265
D = (0.05’’)(384 000 km)/(206265) = 0.93 km = 93 m (BTW…this is why even the best telescopes could never resolve
the image of a person standing on the Moon…unless they stood 93 m high!)
42. Label the phases of the Moon. Indicate phase name below its image.
New Moon
Waxing
Crescent
1st Quarter
Waxing
Gibbous
Full Moon
Waning
Gibbous
3rd Quarter
Waning
Crescent
43. Label the lunar eclipse diagram below. Write answers next to the appropriate letters.
A: Sun
B: Earth
C: Moon
D: Penumbra
E: Umbra
44. Label the solar eclipse diagram below. Write answers next to the appropriate letters.
F: Moon
G: Sun
H: Umbra
I: Penumbra
J: Earth
45. Explain why we do not see a solar eclipse at every new moon.
We do not see a solar eclipse at every new moon because the plane of the Moon’s orbit is tilted by about 5
to the plane of the Earth’s orbit (the ecliptic).
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46. Why do we always see the same side of the Moon?
We always see the same side of the Moon because the Moon is in synchronous rotation with the Earth.
This means that the amount of time it takes the Moon to rotate on its axis is the same as the amount of time
it takes the Moon to revolve around the Earth (a.k.a. ‘spin-orbit coupling’).
47. What is the difference between ‘waxing’ and ‘waning’? between ‘crescent’ and ‘gibbous’?
‘Waxing’ means approaching full moon phase, while ‘waning means approaching new moon phase.
‘Crescent means that less than half of the Moon appears illuminated, while ‘gibbous’ means more than
half of the Moon appears illuminated.
48. Describe different types of solar eclipses. Use the solar eclipse diagram above in your explanation.
For a total eclipse to occur, the Moon's angular diameter must be greater than that of the Sun. Areas on the Earth
upon which the umbra of the Moon’s shadow fall experience a total solar eclipse. Areas on the Earth upon which the
penumbra of the Moon’s shadow fall experience a partial solar eclipse. Occasionally, the Moon is too far away to
completely cover the Sun, and in this case the eclipse is called annular.
49. Describe different types of lunar eclipses. Use the lunar eclipse diagram above in your explanation.
A total lunar eclipse occurs when the Moon passes entirely through the umbra of the Earth’s shadow.
When the Moon passes through the penumbra, a penumbral lunar eclipse occurs. When the Moon is in
between the umbra and penumbra, a partial lunar eclipse occurs.
50. One sidereal month is 27.3 days. One synodic month is 29.5 days. Explain this difference.
The sidereal month is the time that the Moon takes to go around the Earth once relative to the stars.
The synodic month is the time that the Moon takes to go around the Earth relative to the Sun. The synodic
o
month is longer by about 2.3 days. During the sidereal month the Sun appears to move about 27 due to
the Earth’s orbital motion. It takes the extra 2.3 days for the Moon to catch up to the Sun.
51. How would the lunar phase cycle change if the Moon orbited in the same direction but with twice the speed?
The length of the phase cycle would be half as long as it is now.
52. Describe how Eratosthenes measured the circumference of the Earth.
Eratosthenes knew that the Sun never appeared at the zenith at his home in the Egyptian city of Alexandria,
which is on the Mediterranean Sea almost due north of Syene. Rather, on the summer solstice in Alexandria,
the position of the Sun at local noon was about 7° south of the zenith. This angle is about one-fiftieth of a
complete circle, so he concluded that the distance from Alexandria to Syene must be about one-fiftieth of
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Earth’s circumference. In Eratosthenes’s day, the distance from Alexandria to Syene was said to be 5000 stades.
Therefore, Eratosthenes found Earth’s circumference to be
50 X 5000 stades = 250,000 stades
Unfortunately, no one today is sure of the exact length of the Greek unit called the stade. One guess is that
the stade was about one-sixth of a kilometer, which would mean that Eratosthenes obtained a circumference
for Earth of about 42,000 kilometers. This is remarkably close to the modern value of 40,000 kilometers.
53. Describe how Aristarchus determined the relative sizes of the Earth, Moon and Sun.
From his observations of how long the Moon takes to move through Earth’s shadow during a lunar eclipse,
Aristarchus estimated the diameter of Earth to be about 3 times larger than the diameter of the Moon. To determine
the diameter of the Sun, Aristarchus simply pointed out that the Sun and the Moon have the same angular size in the
sky. Therefore, their diameters must be in the same proportion as their distances. In other words, because
Aristarchus thought the Sun to be 20 times farther from Earth than the Moon, he concluded that the Sun must
be 20 times larger than the Moon. Once Eratosthenes had measured Earth’s circumference, astronomers of the
Alexandrian school could estimate the diameters of the Sun and Moon as well as their distances from Earth.
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