Deck 25: Celestial Timekeeping and Navigation

Question 1

Which of the following statements about sidereal and solar days is not true?

A)A solar day is 4 minutes longer than a sidereal day.
B)A solar day represents more than 360° of rotation for Earth.
C)The time it takes for a star to make one circuit of our sky is one sidereal day.
D)The time it takes for the Sun to make one circuit of our sky is one solar day.
E)The time it takes for the Moon to make one circuit of our sky is one solar day.

Answer 1

E

Question 2

Suppose you live at latitude 40°N.Which of the following describes the conditions that make a star circumpolar?

A)Stars are circumpolar if they have declination > +50°.
B)Stars are circumpolar if they have declination > +40°.
C)Stars are circumpolar if they have right ascension > 6 hr.
D)Stars are circumpolar if they have right ascension < 6 hr.
E)No stars are circumpolar at this latitude.

Answer 2

A

Question 3

What is the hour angle of a star crossing your meridian?

A)-6 hours
B)0 hours
C)6 hours
D)It depends on your latitude.
E)It depends on the right ascension of the star.

Answer 3

B

Question 4

Which of the following best describes the Tropic of Cancer?

A)It is any place where it is always very warm.
B)It is another name for the equator.
C)It is a place where the Sun appears to remain stationary in the sky.
D)It is a place where the Sun is directly overhead at noon on the summer solstice.
E)It is a place where the Sun is directly overhead at noon on the spring equinox.

Question 5

Suppose the date is March 21 and the Sun passes through your zenith at noon.Where are you?

A)the equator
B)the Tropic of Cancer
C)the Tropic of Capricorn
D)the Arctic Circle
E)the Antarctic Circle

Question 6

Our calendar has leap years because

A)there is one more sidereal day in a year than solar days.
B)a tropical year is slightly more than 365 days.
C)there is a difference between a sidereal year and a tropical year.
D)the perihelion of Earth's orbit is slowly advancing.

Question 7

The lunar month is longer than the sidereal month because

A)the Moon completes the cycle of lunar phases before it completes a full orbit around Earth.
B)the Moon has to complete more than one full orbit around Earth to complete the cycle of lunar phases.
C)the Moon orbits Earth faster than Earth orbits the Sun.
D)the Moon orbits Earth faster than Earth rotates.
E)the lunar month is based on the Moon's orbit,while the sidereal month is based on Earth's orbit.

Question 8

Based on our current Gregorian calendar,which of the following years is not a leap year?

A)2000
B)2004
C)2008
D)2012
E)All of the above are leap years.

Question 9

What kind of time can be read directly from a sundial?

A)apparent solar time
B)mean solar time
C)standard time
D)daylight saving time
E)sidereal time

Question 10

Suppose you live at latitude 40°N.Which of the following describes the path of the celestial equator through your sky?

A)It goes from due south on your horizon,to your zenith,to due north on your horizon.
B)It goes from due east on your horizon,to your zenith,to due west on your horizon.
C)It goes from due east on your horizon,to an altitude of 50° in the south,to due west on your horizon.
D)It goes from due east on your horizon,to an altitude of 40° in the south,to due west on your horizon.
E)It goes from due east on your horizon,to an altitude of 40° in the north,to due west on your horizon.

Question 11

Which of the following is the reason for the leap years?

A)precession of Earth's axis
B)the tilt of Earth's axis
C)the combined effect of the rotation of Earth and its orbit about the Sun
D)Earth year being a non-integer number of Earth days
E)the non-circular orbit of Earth around the Sun

Question 12

The Sun is rising in the east and will be on your meridian in 2 hours.What time is it?

A)2 A.M.
B)2 P.M.
C)10 A.M.
D)10 P.M.
E)noon

Question 13

The time between rising and setting of a star

A)is always 12 hours.
B)depends on the star's declination.
C)depends on the star's right ascension.
D)depends on the observer's latitude.
E)depends on the observer's longitude.

Question 14

The amount of time between successive passes of any given star across the meridian is

A)23 hours 56 minutes.
B)24 hours.
C)365.25 days.
D)12 years.
E)26,000 years.

Question 15

Suppose you lived at Earth's equator.Which of the following statements would not be true?

A)The north celestial pole is directly on your horizon,due north (with Polaris quite nearby).
B)The south celestial pole is directly on your horizon,due south.
C)Every day of the year,the Sun is above your horizon for 12 hours and below it for 12 hours.
D)The celestial equator goes through your sky from due east on your horizon,through 50° altitude in the south,to due west on the horizon.
E)No stars are circumpolar.

Question 16

The average length of a solar day is

A)23 hours 56 minutes.
B)24 hours.
C)365.25 days.
D)12 years.
E)26,000 years.

Question 17

Which of the following is the reason for the solar day being longer than a sidereal day?

A)precession of Earth's axis
B)the tilt of Earth's axis
C)the combined effect of the rotation of Earth and its orbit about the Sun
D)Earth year being a non-integer number of Earth days
E)the non-circular orbit of Earth around the Sun

Question 18

Suppose the date is March 21 and the Sun crosses your meridian at an altitude of 23.5° in the north.Where are you?

A)the equator
B)the Tropic of Cancer
C)the Tropic of Capricorn
D)the Arctic Circle
E)the Antarctic Circle

Question 19

The south celestial pole appears on your meridian at an altitude of 30° in the south.Where are you?

A)latitude = 30°S
B)latitude = 60°S
C)latitude = 30°N
D)latitude = 60°N
E)the South Pole

Question 20

All the following statements are true.Which one explains why mean solar time differs from apparent solar time?

A)The length of a solar day is not always exactly 24 hours.
B)Earth's rotation period is actually about 23 hours 56 minutes,not 24 hours.
C)Earth's axis precesses with a period of 26,000 years.
D)The Sun reaches the meridian at different times at different longitudes within the same time zone.
E)The path of the Sun through the sky depends on both latitude and date.

Question 21

The constellation shaped like a W is

A)Cassiopeia.
B)Pegasus.
C)Canis Major.
D)Taurus.
E)Andromeda.

Question 22

Our calendar is based on the length of the tropical year rather than the sidereal year.

Question 23

Which of the following explains why navigators a few hundred years ago found it much more difficult to determine their longitude than their latitude?

A)Determining longitude requires mathematical techniques that were not known at the time.
B)Determining longitude without modern instruments requires being able to see the Moon.
C)Determining longitude requires much more precise measurements of angles in the sky than does latitude.
D)Determining longitude requires having an accurate clock.

Question 24

The celestial coordinates of the Sun change from day to day.

Question 25

No matter where you live on Earth,except the poles,your meridian extends from due south on your horizon,through your zenith,to due north on your horizon.

Question 26

Suppose the date is June 21 and the Sun never sets,just touching your northern horizon at midnight.Where are you?

A)the equator
B)the Tropic of Cancer
C)the Tropic of Capricorn
D)the Arctic Circle
E)the Antarctic Circle

Question 27

No matter where you live on Earth,the Sun is always directly overhead at noon.

Question 28

The Sun is on your meridian,and you have a UT clock that tells you it is midnight in Greenwich.What is your longitude?

A)12° west of Greenwich
B)12° east of Greenwich
C)60° west of Greenwich
D)60° east of Greenwich
E)180° of longitude from Greenwich

Question 29

The three bright stars that make up the Winter Triangle are

A)Polaris,Aldebaran,and Algol.
B)Polaris,Betelgeuse,and Sirius.
C)Betelgeuse,Procyon,and Sirius.
D)Betelgeuse,Rigel,and Aldebaran.
E)Capella,Procyon,and Sirius.

Question 30

Which of the following statements about Betelgeuse is not true?

A)It is distinctly red in color.
B)We now know that it is a very massive star near the end of its life.
C)Its Arabic name means "the demon star."
D)It is one star of the three stars of the Winter Triangle,along with Procyon and Sirius.
E)It is the upper left shoulder star of the constellation Orion.

Question 31

The three stars of the Summer Triangle are

A)Antares,Arcturus,and Spica.
B)Arcturus,Vega,and Algol.
C)Deneb,Spica,and Vega.
D)Vega,Deneb,and Altair.
E)Altair,Antares,and Arcturus.

Question 32

All directions are south from the North Pole.

Question 33

The coordinates used to locate a position on the celestial sphere are altitude and declination.

Question 34

The summer solstice is east of the vernal equinox by 6 hours of right ascension.

Question 35

The Sun is on your meridian,and you have a UT clock that tells you it is 3 P.M.in Greenwich.What is your longitude?

A)3° west of Greenwich
B)3° east of Greenwich
C)45° west of Greenwich
D)45° east of Greenwich
E)30° west of Greenwich

Question 36

Each of the following lists a constellation and a bright star.In all cases but one,the star is part of the constellation.Which one is the mismatch?

A)Scorpio,Vega
B)Cygnus,Deneb
C)Boötes,Arcturus
D)Virgo,Spica
E)Auriga,Capella

Question 37

All of the following are true.Which of the following gives evidence that Earth's orbit is not perfectly circular?

A)The Sun's angular size changes throughout the year.
B)Earth's seasons are not of exactly equal length.
C)In North America,it is hotter in July than January.
D)Both A and C
E)Both A and B

Question 38

On the equator,days and nights are always 12 hours long,no matter what time of year.

Question 39

The constellation shaped like a big square (the "great square of ...")is

A)Cassiopeia.
B)Pegasus.
C)Canis Major.
D)Taurus.
E)Andromeda.

Question 40

No matter where you live on Earth,the Sun always rises and sets each day.

Question 41

The Winter Triangle is formed by the stars Betelgeuse,Rigel,and Aldebaran.

Question 42

Note to instructors: The following question assumes you gave a "lost at sea" question on your midterm.

Question 43

For the following questions,refer to Figure S1.1,which shows a portion of the sky visible in the early evenings in the fall.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which bright star (lowercase letters)is Aldebaran?

Question 44

For vacation,you decide to take a solo boat trip.While contemplating the universe,you lose track of your location.Fortunately,you have some astronomical tables and instruments,as well as a UT clock.You thereby put together the following description of your situation:
a.What is your latitude? How do you know?
b.What is your longitude? How do you know?

Question 45

For vacation,you decide to take a solo boat trip.While contemplating the universe,you lose track of your location.Fortunately,you have some astronomical tables and instruments,as well as a UT clock.You thereby put together the following description of your situation:
∙ Your local time is midnight.
∙ Polaris appears at an altitude of 67° in the north.
∙ The UT clock reads 01:00.
a.What is your latitude? How do you know?
b.What is your longitude? How do you know?

Question 46

For vacation,you decide to take a solo boat trip.While contemplating the universe,you lose track of your location.Fortunately,you have some astronomical tables and instruments,as well as a UT clock.You thereby put together the following description of your situation:
∙ It is the day of the summer solstice.
∙ The Sun is on your meridian at an altitude of 67.5° in the north.
∙ The UT clock reads 06:00.
a.What is your latitude? How do you know?
b.What is your longitude? How do you know?

Question 47

For the following questions,refer to Figure S1.1,which shows a portion of the sky visible in the early evenings in the fall.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which constellation (capital letters)is Pegasus?

Question 48

Suppose that you live in Sydney,Australia (latitude 34°S).Describe the path of the Sun through your sky for each of the following days:
a.the day of the spring equinox
b.the day of the summer solstice
c.the day of the winter solstice

Question 49

For the following questions,refer to Figure S1.1,which shows a portion of the sky visible in the early evenings in the fall.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which constellation (capital letters)is Cassiopeia?

Question 50

A year at the south pole consists of 6 months of darkness and 6 months of daylight.

Question 51

For vacation,you decide to take a solo boat trip.While contemplating the universe,you lose track of your location.Fortunately,you have some astronomical tables and instruments,as well as a UT clock.You thereby put together the following description of your situation:
∙ It is the day of the spring equinox.
∙ The Sun is on your meridian at an altitude of 75° in the south.
∙ The UT clock reads 22:00.
a.What is your latitude? How do you know?
b.What is your longitude? How do you know?

Question 52

For the following questions,refer to Figure S1.1,which shows a portion of the sky visible in the early evenings in the fall.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which constellation (capital letters)is Taurus?

Question 53

The Summer Triangle is formed by the stars Deneb,Vega,and Altair.

Question 54

Suppose you live at the equator.Describe the path of the Sun through your sky for each of the following days:
a.the day of the spring equinox
b.the day of the summer solstice
c.the day of the winter solstice

Question 55

Suppose you live at the North Pole.Describe the path of the Sun through your sky for each of the following days:
a.the day of the spring equinox
b.the day of the summer solstice
c.the day of the winter solstice

Question 56

Your Local Sky
a.Where is the north (or south)celestial pole in your sky?
b.Describe the meridian in your sky.
c.Describe the celestial equator in your sky.
d.What is the range of declinations that makes a star circumpolar in your sky? Explain.
e.Describe the path of the Sun through your sky on the fall equinox.
f.Describe the path of the Sun through your sky on the winter solstice.

Question 57

For the following questions,refer to Figure S1.1,which shows a portion of the sky visible in the early evenings in the fall.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which constellation (capital letters)is Auriga?

Question 58

For the following questions,refer to Figure S1.1,which shows a portion of the sky visible in the early evenings in the fall.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which constellation (capital letters)is Perseus?

Question 59

For the following questions,refer to Figure S1.1,which shows a portion of the sky visible in the early evenings in the fall.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which bright star (lowercase letters)is Capella?

Question 60

For the following questions,refer to Figure S1.1,which shows a portion of the sky visible in the early evenings in the fall.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which bright star (lowercase letters)is Algol,the "demon star"?

Question 61

Choose the appropriate star from Table S1.1 for the following questions:
Table S1.1

Suppose you live at latitude 20°N.Which star passes closest to your zenith on its daily path through your sky?

Question 62

For the following questions,refer to Figure S1.2,which shows a portion of the sky visible in the early evenings in winter.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which constellation (capital letters)is Orion?

Question 63

Choose the appropriate star from Table S1.1 for the following questions:
Table S1.1

Suppose you live at latitude 30°N.Which star is never visible in your sky?

Question 64

For the following questions,refer to Figure S1.2 which shows a portion of the sky visible in the early evenings in winter.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which constellation (capital letters)is Canis Minor?

Question 65

For the following questions,refer to Figure S1.2 which shows a portion of the sky visible in the early evenings in winter.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which bright star (lowercase letters)is Aldebaran?

Question 66

For the following questions,refer to Figure S1.2 which shows a portion of the sky visible in the early evenings in winter.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which bright star (lowercase letters)is Sirius?

Question 67

For the following questions,refer to Figure S1.2 which shows a portion of the sky visible in the early evenings in winter.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which bright star (lowercase letters)is Rigel?

Question 68

Choose the appropriate star from Table S1.1 for the following questions:
Table S1.1

Suppose it is late June.Which star crosses your meridian around midnight? Assume you live at a latitude where all the stars on this list rise above your horizon each day.

Question 69

Choose the appropriate star from Table S1.1 for the following questions:
Table S1.1

Suppose you live at latitude 20°S.Which star passes closest to your zenith on its daily path through your sky?

Question 70

Choose the appropriate star from Table S1.2 for the following questions:
Table S1.2

Which star remains above the horizon for the longest time each day at latitude 40°N?

Question 71

For the following questions,refer to Figure S1.2 which shows a portion of the sky visible in the early evenings in winter.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which bright star (lowercase letters)is Betelgeuse?

Question 72

Choose the appropriate star from Table S1.1 for the following questions:
Table S1.1

Which star lies closest to the south celestial pole on the celestial sphere?

Question 73

Choose the appropriate star from Table S1.1 for the following questions:
Table S1.1

Which star lies closest to the celestial equator on the celestial sphere?

Question 74

Choose the appropriate star from Table S1.2 for the following questions:
Table S1.2

Which star can never be seen at latitude 40°N?

Question 75

For the following questions,refer to Figure S1.2,which shows a portion of the sky visible in the early evenings in winter.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which constellation (capital letters)is Canis Major?

Question 76

For the following questions,refer to Figure S1.2,which shows a portion of the sky visible in the early evenings in winter.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which constellation (capital letters)is Taurus?

Question 77

Choose the appropriate star from Table S1.2 for the following questions:
Table S1.2

Which star appears nearest to the south celestial pole?

Question 78

Choose the appropriate star from Table S1.1 for the following questions:
Table S1.1

Which star lies closest to the north celestial pole on the celestial sphere?

Question 79

For the following questions,refer to Figure S1.2 which shows a portion of the sky visible in the early evenings in winter.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which bright star (lowercase letters)is Procyon?

Question 80

For the following questions,refer to Figure S1.2,which shows a portion of the sky visible in the early evenings in winter.Note that five bright stars are labeled with lowercase letters and five constellations are labeled with capitals.A few hints are also given.

Which constellation (capital letters)is Gemini?