UARK Astronomy HW #2
Suppose you use the Southern Cross to determine that the south celestial pole appears 40 degrees above your horizon. Then you must be located at _________.
latitude 40 degrees south
An angle of 1 arcsecond is _________.
less than the thickness of a human hair held at arm's length
Again consider the position of the Moon shown in part A. How much of the Moon's surface is covered by Earth's shadow?
none
Again consider the position of the Moon shown in part A. What does the Moon look like in our sky at this time?
waxing crescent
The shadow cast by a simple stick or obelisk allowed ancient people to
tell the time of day
The Sun's path, as viewed from the equator, is highest in the sky on _________.
the March and September equinoxes
This diagram represents a person's local sky. What does the red semicircle represent?
the Meridian
This diagram represents a simplified model of the celestial sphere. The unlabeled circle that is highlighted in purple represents __________.
the celestial equator
If our year were twice as long (that is, if Earth took twice as many days to complete each orbit around the Sun), but Earth's rotation period and axis tilt were unchanged, then _________.
the four seasons would each be twice as long as they are now
Which of the following planets has essentially no seasons at all?
Jupiter (axis tilt = 3.1°)
What is the approximate latitude and longitude of the South American location marked by the black dot on this diagram?
Latitude = 15°S, longitude = 45°W
Based on what you have learned from your rankings in Parts A and B, which of the following planets would you expect to have seasons most like Earth's?
Mars (axis tilt = 25.2°)
Which of the following statements about constellations is false?
Most constellations will be unrecognizable hundreds of years from now.
When would you expect to see Venus high in the sky at midnight?
Never
A total solar eclipse can only happen during what lunar phase?
New
Suppose it is full moon. What phase of Earth would someone on the Moon see at this time?
New Earth
The Sun-centered system pictured in the lower window of the video offers a simple explanation for observations of apparent retrograde motion. Should these facts alone have been enough to convince the ancient Greeks that Earth really does go around the Sun?
No, because the Greeks had an Earth-centered model that also accounted for apparent retrograde motion.
In the Northern Hemisphere, the day that the Sun is up the longest in the sky is on the June solstice.
True
Which of the following planets should have the most extreme seasons?
Uranus (axis tilt = 97.9°)
The Andromeda Galaxy is faintly visible to the naked eye in the constellation Andromeda. Suppose instead it were located in the same direction in space as the center of the Milky Way Galaxy (but still at its current distance). How would it appear to the eye in that case?
We could not see it at all.
In Ptolemy's Earth-centered model for the solar system, Venus always stays close to the Sun in the sky and, because it always stays between Earth and the Sun, its phases range only between new and crescent. The following statements are all true and were all observed by Galileo. Which one provides evidence that Venus orbits the Sun and not Earth?
We sometimes see gibbous (nearly but not quite full) Venus.
Suppose that instead of being inclined to Earth's orbit around the Sun, the Moon's orbit was in the same plane as Earth's orbit around the Sun. In this hypothetical situation, approximately how many solar eclipses would occur each year?
12
When traveling north from the United States into Canada, you'll see the North Star (Polaris) getting _________.
Higher in the sky
In reality, the Moon's orbit about Earth is tilted (by about 5°) with respect to Earth's orbit about the Sun. As a result, the actual number of solar eclipses that occur each year is approximately _____.
2
Which position in this diagram represents Earth on the day that we have the longest amount of daylight in the continental United States?
2
Which position in this diagram represents Earth at the beginning of spring for the Southern Hemisphere?
3
You observe a full moon rising at sunset. What will you see at midnight?
A full moon high in the sky
During the period each year when we see Mars undergoing apparent retrograde motion in our sky, what is really going on in space?
Earth is catching up with and passing by Mars in their respective orbits.
What is really happening in space during the periods when we see Mars going through apparent retrograde motion?
Earth is passing by Mars in its orbit around the Sun
Kepler's first law states that the orbit of each planet is an ellipse with the Sun at one focus. Which of the following statements describe a characteristic of the solar system that is explained by Kepler's first law?
Earth is slightly closer to the Sun on one side of its orbit than on the other side, The Sun is located slightly off-center from the middle of each planet's orbit.
For most of history, the lack of observable stellar parallax was interpreted to mean that _________.
Earth is stationary at the center of the universe
The Sun rises and sets each day because
Earth rotates once each day
Consider the Moon when it is in the position shown in the moon phase diagram below. How much of the Moon's total surface is illuminated by sunlight at this time?
Exactly half
The science of astrology (studying effects of the planets on our lives) exists as an alternative scientific methodology to astronomy.
False
Which photo shows what the Moon looks like when it is in the position shown in the following moon phase diagram?
Full
Which of the following best summarizes the reason we see phases of the Moon?
Half the Moon is always illuminated by the Sun, but the phase we see depends on how much of this half we are looking at from Earth.
Kepler's third law states that a planet's orbital period, p, is related to its average (semimajor axis) orbital distance, a, according to the mathematical relationship p2=a3. Which of the following statements describe a characteristic of the solar system that is explained by Kepler's third law?
Inner planets orbit the Sun at higher speeds than outer planets, Venus orbits the Sun faster than Earth orbits the Sun
How does Earth's varying distance from the Sun affect our seasons?
It doesn't. Earth's orbital distance plays no significant role in the seasons.
Kepler's second law states that as a planet orbits the Sun, it sweeps out equal areas in equal times. Which of the following statements describe a characteristic of the solar system that is explained by Kepler's second law?
Pluto moves faster when it is closer to the Sun than when it is farther from the Sun.
Refer to the data in the introduction. Rank the seasons for the Southern Hemisphere based on Earth's distance from the Sun when each season begins, from closest to farthest.
Summer, Fall, Spring, Winter
Which of the following statements about the celestial sphere is not true?
The "celestial sphere" is another name for our universe.
Suppose Earth's axis tilt was significantly greater than its current 23.5 degrees, but Earth's rotation period and orbital period were unchanged. Which statement below would not be true?
The length of each season (for example, the number of days from the summer solstice to the fall equinox) would be significantly longer than it is now.
All the following statements are true. Which one explains the reason that there is not a solar eclipse at every new moon?
The orbital plane of the Moon is tilted slightly (by about 5 degrees) to the ecliptic plane.
What conditions must exist for a lunar eclipse to occur?
The phase of the Moon must be full and the Moon must be passing through Earth's orbital plane.
What conditions must exist for a solar eclipse to occur?
The phase of the Moon must be new and the Moon must be passing through Earth's orbital plane.
In the Greek geocentric model, the retrograde motion of a planet occurs when:
The planet actually goes backward in its orbit around Earth.
What happens during the apparent retrograde motion of a planet?
The planet appears to turn around in its eastward path through the stars and backs up for many nights traveling westwardly.
You've now seen that Earth's varying distance cannot be the cause of our seasons. So what is the cause of the seasons?
The tilt of Earth's axis causes different portions of the Earth to receive more or less direct sunlight at different times of year.
Based on what you have learned from your rankings in Parts A and B, which statement best describes how variation in the Earth-Sun distance affects the seasons?
The variation in Earth-Sun distance over the course of each year has virtually no effect on the seasons.
It's 6 am and the Moon is at its highest point in your sky (crossing the meridian). What is the Moon's phase?
Third quarter
Suppose you are facing north and you see the Big Dipper close to your northern horizon, with Polaris (and the Little Dipper) above it. Where will you see the Big Dipper in six hours?
To the right of Polaris; that is, 90 degrees counterclockwise from its current position
Refer to the data in the introduction. Rank the seasons for the Northern Hemisphere based on Earth's distance from the Sun when each season begins, from closest to farthest.
Winter, Spring, Fall, Summer
Suppose you live in the United States and you see a crescent moon in your evening sky tonight. What will a friend in South America see tonight?
Your friend will also see a crescent moon.
If the Moon is 3rd quarter phase, what shape does it have in the sky?
a half circle
We cannot see a new moon in our sky because _________.
a new moon is quite near the Sun in the sky
Suppose you see a photo showing Jupiter half in sunlight and half in shadow (that is, a first-quarter Jupiter). This photo might have been taken by _________.
a spacecraft orbiting Jupiter
What is a circumpolar star?
a star that always remains above your horizon
Diagrams like this one are commonly used in discussions of seasons and they can be quite useful. However, this diagram greatly exaggerates ______________________
all of the answers.
Imagine that Venus is in its full phase today. If we could see it, at what time would the full Venus be highest in the sky?
at Noon
When would a new Venus be highest in the sky?
at Noon
Consider a time when Mars is in the middle of one of its periods of apparent retrograde motion. During this time, Mars appears ______ in our night sky and crosses the meridian around _________
brightest, midnight
At most times, Mars appears to move _____ relative to the stars. The exceptions are during its periods of apparent retrograde motion, when Mars appears to move ______ relative to the stars.
eastward, westward
As seen from Earth, the Sun appears to follow the annual path that we call the __________ around the celestial sphere.
ecliptic
During a lunar eclipse the Moon's phase must be
full
In Ptolemy's Earth-centered model for the solar system, Venus's phase is never full as viewed from Earth because it always lies between Earth and the Sun. In reality, as Galileo first recognized, Venus is __________.
full whenever it is on the opposite side of the Sun from Earth
Which of the following statements about phases of the Moon are true? Select all that apply.
if it is full moon, the Moon will rise around sunset at new moon, we see only the "night" side of the Moon the time between new moon and full moon is about two weeks at new moon, the half of the Moon facing the Sun is fully illuminated
In any particular place on Earth, certain constellations are visible in the evening only at certain times of the year because _________.
our evening view of space depends on where Earth is located in its orbit around the Sun
If you wanted to document the apparent retrograde motion of Mars, you would need to measure and record Mars' ________ over a period of ______ .
position among the constellations, several months
The Sun
seems to move around the celestial sphere daily to the East.
This multiple exposure photograph shows the apparent retrograde motion of Mars. To make this picture, the photographer needed to combine individual photos of Mars taken over a period of _________.
several months
