Chapter 2:
88- In a penumbral lunar eclipse,
all parts of the Moon are partially (not totally) shaded from the Sun.
The synodic or lunar month is the time
approximately 29½ days) between identical phases of the moon; e.g. from full moon to full moon.
Scales
are very large: measure in light-years, the distance light travels in a year—about 10 trillion miles
91- The Moon does not look completely dark when it is in the Earth's shadow during a total solar eclipse because
atmospheric refraction bends red solar light onto the Moon.
15- Which of the following statements describing the situation at a mid-latitude site at the time of equinox is correct?
Day and night are of equal length.
45- Why do we see different phases of the Moon?
The illuminated half of the Moon becomes more or less visible from Earth as the Moon orbits the Earth.
Purpose of constellations?
The time to plant seeds was predicted from i. the positions of the constellations; ii. the height of the noontime Sun. Planning sea travel often depended on the tides, which are influenced by the positions of the Moon and the Sun. The positions of the Sun in the day and the constellations at night were used for navigation at sea. In particular, the North Star, Polaris, was very important in navigation (in the northern hemisphere), because it closely marks the direction of due north, and its altitude in the sky gives the latitude from which it is observed.
87- During which type of lunar eclipse does the Moon remain longest in the Earth's shadow?
Total
16- How often does the Sun cross the celestial equator in a given year?
Twice
63- A full Moon will always be at its highest in our sky at about
midnight.
48- If the Moon is between the Sun and the Earth and almost in line with the Sun, we call its phase
new Moon.
9- At what time of the year will the shadow of a vertical pole (a sundial) at any site in the northern hemisphere be the shortest?
noon, June 21, at the beginning of summer
82- If the plane of the Moon's orbit were the same as the ecliptic plane, there would be a lunar eclipse
once per month.
55- How much of the total surface of the Moon is illuminated by the Sun when it is at quarter phase?
one half
68- One synodic month is longer than
one sidereal month by about 2.2 days.
14- The vernal equinox is
one time of the year when the Sun crosses the celestial equator.
75- There is about a 5° angle between the
orbit of the Moon and the plane of the ecliptic, or the Earth's orbit.
76- The line of nodes of the Moon's orbit is the line of intersection of the
orbit with the ecliptic plane
81- A lunar eclipse does not occur at every full Moon because the
plane of the Moon's orbit is at an angle to the plane of the Earth's orbit.
99- The accurate prediction of the time and position of a total solar eclipse is
relatively easy since the motions of Earth and Moon in space are predictable and accurately known.
83- The maximum number of eclipses (both solar and lunar) that can occur in one calendar year is
seven.
34- The true orbital period of the Earth around the Sun, defined as the time taken to complete one orbit with respect to the background stars, is one
sidereal year.
35- The time that elapses before the Sun returns to the same point in space in the solar system compared to the background stars in our sky is one
sidereal year.
40- Precession is the
slow coning motion of the spin axis of the Earth, similar to that of a spinning top.
5- In the southern hemisphere, summertime occurs when
sunlight falls more directly on this hemisphere, heating it more than at other times of the year.
3- Summertime in the northern hemisphere is when
sunlight falls more directly on this hemisphere, heating it more than average.
6- Winter in the northern hemisphere occurs when
sunlight falls most obliquely on that region of the Earth.
64- Full Moon can be on the horizon only at
sunrise or sunset.
2- The reason Earth experiences seasons is
that Earth's rotation axis is not perpendicular to the ecliptic.
50- On a given evening, you notice that the sunlit portion of the Moon has a crescent shape. This simple observation tells you
that the Moon is closer to the Sun than the Earth is on that evening.
7- When the northern hemisphere is experiencing winter,
the Earth is closer to the Sun than it is during northern summer.
44- The tropical year is different from the sidereal year because
the Earth precesses on its axis.
27- In general, a sundial is NOT a good timekeeper because
the Earth's orbital speed around the ecliptic is variable.
Our solar system is named
the Milky Way
74- The total number of eclipses is limited to seven or fewer per year because one condition that must be met for a lunar or solar eclipse is that
the Moon be close to or crossing the ecliptic plane.
78- A solar eclipse can occur ONLY when
the Moon comes between the Earth and the Sun.
84- A lunar eclipse is caused by
the Moon passing into the shadow of the Earth.
95- During a particular solar eclipse (when the Moon and Sun are precisely in line), the eclipse can be either total (Sun completely covered) or annular (Sun not quite covered) when viewed from the eclipse centerline because
the Moon's distance from the Earth varies from eclipse to eclipse.
20- The autumnal equinox is the time of the year when
the Sun crosses the equatorial plane, moving south.
13- The "Land of the Midnight Sun" is so-named because
the Sun is above the horizon for a full 24 hours at a certain time of the year.
23- At the summer solstice in the northern hemisphere,
the Sun is at its highest angle in the sky for the whole year.
92- The difference between an umbral eclipse and a penumbral eclipse is
the distance of the Moon above or below the ecliptic.
42- Precession of the Earth's axis of rotation is caused by
the gravitational pull of the Moon and the Sun on the equatorial bulge of the Earth.
4- Summertime in the northern hemisphere is when
the northern hemisphere is tilted toward the Sun.
73- What is the phase of the Moon when it rises at midnight? You may want to sketch a diagram to work this out. Earth rotates toward the east, and the Moon's motion around Earth is also eastward.
third quarter
94- A total solar eclipse is visible (assuming clear skies everywhere)
to only people in a long narrow path, much smaller than a hemisphere.
36- The time that elapses before the Sun returns to the position of the vernal equinox in our sky is known as one
tropical year.
39- Precession is the
very slow coning motion of the Earth's axis of rotation.
46- Which of the following is the correct sequence of appearances of Moon phases in the sky?
waxing crescent, first quarter, waxing gibbous, full Moon
59- The full Moon always occurs
when the Moon is farther from the Sun than the Earth is.
How far is earth from the Sun?
93 million miles (One Astronomical unit)
29- The direction of Earth's rotation about its axis is the same as the direction of its revolution about the Sun. How does a solar day compare to a sidereal day on Earth?
A solar day is always longer.
How many starts are visible at one time? But how many are only visible to the human eye at one time?
6,000 and 3,000 but human brain sees half so we actually are exposed to around 9,000
57- When the Moon is at new Moon phase, what percentage of the area of the Moon illuminated by the Sun can we see from the Earth?
0%
89- What is the maximum length of totality for a lunar eclipse?
1 hour 47 minutes
71- The Moon will appear to an observer at midlatitudes on Earth to rise in the east, in solar time, about (You might attempt to verify this by observation!)
1 hour later each evening.
How big across is our galaxy?
100,000 light years across
43- Polaris, the "pole star," is at present within
1° of the north celestial pole.
How many stars are estimated to me in our galaxy?
200 billion
38- Because of precession, how long will it be before the spin axis of the Earth points toward the present pole star again?
26,000 years
70- If you were on the Moon at the dividing line between dark and light (the terminator) at a particular time, say, sunrise, how long would it be before the dividing line returned to your position?
291⁄2 days
28- In winter, clocks in New York (maintaining civil time, or mean solar time) compared to those in California will be
3 hours ahead.
How far is Neptune away from Sun?
3 million miles away
31- Leap-year corrections in the calendar are necessary to account for the fact that one year is not exactly
365 days.
37- The length of the Earth's year at the present time is approximately
3651⁄4 days.
26- Any star (except the Sun), when viewed from low latitudes and midlatitudes, will rise in the east about
4 minutes earlier each evening.
How many galaxies are their in the visible universe?
50 billion = 10 billion trillion stars (10^22)
93- Which of the following factors makes it far more likely that a person will have seen a total lunar eclipse than a total solar eclipse?
A total lunar eclipse can be seen by people on most of the nighttime side of the Earth, whereas a specific total solar eclipse can be seen only by people within a narrow strip of the Earth's surface.
A Galaxy:
A typical galaxy is a collection of a hundred billion stars, each separated by vast regions of nearly empty space. Our Sun is a rather undistinguished star in the Milky Way.
8- The lowest amount of solar energy per square meter is incident on the surface of Earth in the northern hemisphere on or about
December 21, the beginning of winter.
21- A particular location in the southern hemisphere experiences the longest day on about
December 21.
90- When in total lunar eclipse, the Moon shows a reddish color because only the red part of the solar spectrum is deflected onto it by the
Earth's atmosphere.
96- What is the major factor that governs whether a solar eclipse is total rather than annular when viewed from the center of the eclipse path on Earth?
Earth-Moon distance
What is constellation Orion?
Greek hunter
24- How would the Sun appear to move in the sky if you were at the South Pole on a midsummer day?
It would appear to move parallel to the horizon at an elevation angle of about 23.5° for a full 24 hours.
32- The person who introduced the leap year into our calendar was
Julius Caesar
22- In the southern hemisphere, day and night are of equal duration on about
March 21.
62- If the Moon is located at the vernal equinox on the first day of spring, what is the phase of the Moon?
New
80- What is the phase of the Moon during a total solar eclipse?
New
53- Approximately what time will the first-quarter Moon rise?
Noon
33- The most recent correction to the calendar to keep the yearly date in tune with the seasons (resulting in the present calendar) was instituted by
Pope Gregory XIII
52- Which of the Moon's phases is most easily seen during the daytime?
Quarter
17- The vernal equinox is the time of the year when the
Sun crosses the equatorial plane, or celestial equator, moving northward.
51- At approximately what time does the crescent Moon just after new Moon rise?
Sunrise
58- Approximately when does a full Moon rise,?
Sunset
68- Why is the period between two successive full Moons NOT equal to the Moon's orbital period, or sidereal month?
The Earth-Moon system is also orbiting the Sun.
79- Which of the following conditions holds for relative distances during a solar eclipse?
The Moon is closer to the Sun than the Earth is.
47- From the northern hemisphere, where in the sky would you expect to see true astronomical new Moon?
The Moon is not visible at new Moon.
86- Which of the following statements describes a necessary condition for lunar or solar eclipses?
The Moon must be close to or crossing the ecliptic plane.
100- What is the cause of an annular eclipse?
The Moon's position in its orbit is near apogee, its farthest point from Earth.
66- The Moon is seen to keep one face toward the Earth at all times. If viewed from a point directly above the plane of the planetary system, how does it have to rotate to maintain this alignment?
The moon must rotate once per month, or once per orbit around the Earth.
Twelve constellations Sun moves through during the year are called the...
Zodiac
41- Precession of the Earth's spin axis results in
a gradual shift of the vernal equinox along the ecliptic.
97- A person standing in the Moon's penumbra will see
a partial solar eclipse.
11- At what average speed does the Sun appear to move across our sky with respect to the stars in order to move through one full circle in one year?
about 1° per day
69- The length of time for the Moon to move from new Moon to new Moon is known as one synodic month. Compared to one full orbital period with respect to the star background, or one sidereal month, the synodic month is
about 2 days longer.
25- If observed carefully night by night, a particular star will be seen to rise
about 4 minutes earlier every night.
12- From the Earth's North Pole, how long does the Sun remain above the horizon once it first appears at the beginning of spring?
about 6 months
98- What is the maximum time of totality for any total solar eclipse observed from the Earth's surface?
about 7.5 minutes
56- How much of the Moon's surface is illuminated by the Sun at quarter-moon phase?
about one half
2 pointer stars?
big dipper to polaris
61- When does the third-quarter Moon rise?
close to midnight
49- At approximately what time does the new Moon rise?
close to sunrise
18- When the Sun is at one of the equinoxes,
day and night are of equal length everywhere on the Earth.
65- The Moon is visible in the sky in the
daytime from most places on the Earth about half the time, or for two weeks in every month.
77- The line of nodes of the Moon's orbit is the
line of intersection between the Moon's orbit and the Earth's orbit (the ecliptic plane).
54- The phase of the Moon when Sun and Moon are separated by 6 hours of right ascension is always
either first or third quarter.
67- Which of the following phrases is the only one that truly and meaningfully describes the side of the Moon away from the Sun?
far side of the Moon
10- At what time of the year in the northern hemisphere will your shadow in sunlight at midday be shortest?
first day of summer, about June 21
85- Eclipses of the Moon can occur only at
full Moon.
60- When the Sun and Moon are separated by 12 hours of right ascension, the phase of the Moon is always
full.
19- The equinoxes are located at the
intersections of the ecliptic and the celestial equator.
A siderial period
is a period measured with respect to the distant stars. The sidereal day is the time (23 hours 56 min.) taken for a planet to make one complete revolution.
72- The motion of the Moon across the sky, against the background of stars,
is approximately 13° per day.
The solar day
is the average time (24 hours) between successive noon-times, as measured at 0o longitude in Greenwich, England (the prime meridian).
A synodic period
is the period measured from a planet (or moon). The solar day is the synodic day measured from Earth, which is longer than the siderial day by about 4 min.
Astronomy
is the study of the universe
The tropical year
is the synodic year, measured between successive vernal equinoxes, which is shorter than the siderial year by about 20 minutes.
The sidereal month
is the time (approximately 27.3 days) it takes the Moon to make one full orbit (360o) around the Earth.
Holistic path
is the way the earth moves around sun and in solar system
1- The Earth would NOT have seasons if
its axis of rotation were perpendicular to its orbital plane.
30- Leap years— years that contain an extra day—are necessary because the
length of a year is not an exact number of days.
What is Astrology?
which makes predictions about individuals based on the star patterns at their birth