Astronomy 1040: Chapter 2 HW

Use the procedure shown in the video to determine the approximate rise, highest point, and set times for different phases of the Moon, then complete the following sentences.

A first quarter moon rises at about noon, reaches its highest point in the sky at about sunset, and sets around midnight.

Use the procedure shown in the video to determine the approximate rise, highest point, and set times for different phases of the Moon, then complete the following sentences.

A full moon rises at about sunset, reaches its highest point in the sky at midnight, and sets around sunrise.

What is the cause of the lunar phases (i.e. why doesn't the Moon look the same every day)?

The Moon's orbit around Earth causes different amounts of the illuminated side of the Moon to be visible from Earth.

For any particular location on Earth, why are lunar eclipses observed more frequently than solar eclipses?

The Moon's shadow covers only a small portion of the Earth.

If we have a new moon today, when we will have the next full moon?

in about 2 weeks

If the Sun rises precisely due east:

it must be the day of either the spring or fall equinox.

Two stars that are in the same constellation:

may actually be very far away from each other.

A total solar eclipse can only happen during what lunar phase?

new

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

Match the correct names for regions of eclipse shadows to their descriptions. Drag words from the left to the blanks in the sentences at the right.

Partial shadow (penumbra): the larger, surrounding region of an object's shadow in which light from the Sun is only partially blocked

Step 2 is to place a person in the position on Earth where the Moon would be overhead or at its highest point in the sky and determine the time for that person. At which of the four numbered positions shown below would the person be seeing the third quarter moon be at its highest point in the sky?

Position 4

For people in Australia, the first day of spring is approximately ____________.

September 21

Sort each item into the correct bin based on whether it describes lunar eclipses or solar eclipses.

Solar eclipse -occurs when the Moon comes directly between Earth and the Sun -occurs when the Moon's shadow falls on Earth -can be seen only along a relatively narrow path on Earth -can occur only at new moon

Why doesn't a total lunar eclipse occur every month?

Sometimes the Moon is above or below Earth's shadow during a full moon.

Not true anywhere on Earth

Sun reaches zenith (altitude 90 degrees) every day at noon

True everywhere on Earth

Sun rises due east and sets due west on March equinox

Why will total solar eclipses no longer be possible after about 600 million years from now?

The Moon will have moved too far from Earth for it to fully block the Sun.

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

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

Why do we essentially see the same face of the Moon at all times?

Because the Moon's rotational and orbital periods are equal.

Suppose the Moon were three times smaller than it really is, but its distance from Earth remained the same. Which type of eclipse would never occur?

Total solar eclipses.

During an annular solar eclipse, ____________.

the Moon is too far away from Earth to block the entire Sun

If a person were standing in the Moon's partial shadow (penumbra) during a solar eclipse, he/she would see ____________.

the Sun with a portion of it blocked by the Moon

In winter, Earth's axis points toward the star Polaris. In spring:

the axis also points toward Polaris.

If you are watching a lunar eclipse in which the Moon is in Earth's partial shadow, you will see ____________.

the entire Moon, but slightly dimmer than normal.

What is the ecliptic?

the path the Sun appears to trace around the celestial sphere each year

A week after full moon, the Moon's phase is:

third quarter.

On Dec. 21, the Sun is directly above the ____________.

tropic of Capricorn (latitude = 23.5 degrees S)

Approximately how often do eclipse seasons occur?

twice a year

True for Northern Hemisphere

- Sun reaches highest point in local sky on June solstice - At high latitudes, Sun never rises on December solstice

True for Southern Hemisphere

- Sun traces shortest path across the local sky on June Solstice - Sun is above horizon for the longest time on December solstice - At high latitudes, Sun never sets on December solstice

Which of the following accurately describe an eclipse season? Select all that apply.

-During an eclipse season, there will be a lunar eclipse at full moon. -During an eclipse season, there will be a solar eclipse at new moon. -An eclipse season occurs when the nodes of the Moon's orbit are lined up with Earth and 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. Closest to the Sun 2nd closest to the Sun 3rd closest to the Sun Farthest from the Sun

-Summer (147.2 million km) -Fall (149.0 million km) -Spring (150.2 million km) -Winter (152.0 million km)

Which of the following statements are true about summer compared to winter?

-The Sun follows a longer and higher path through your sky in summer. -You have more daylight and less darkness in summer. -Temperatures tend to be warmer in summer.

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. Closest to the Sun 2nd closest to the Sun 3rd closest to the Sun Farthest from the Sun

-Winter (147.2 million km) -Spring (149.0 million km) -Fall (150.2 million km) -Summer (152.0 million km)

Which of the following statements about phases of the Moon are true? Select all that apply. Select all that apply.

-if it is full moon, the Moon will rise around sunset -the time between new moon and full moon is about two weeks -at new moon, we see only the "night" side of the Moon -at new moon, the half of the Moon facing the Sun is fully illuminated

What conditions must exist for a lunar eclipse to occur? Select all that apply.

-it must be full moon -the Moon must be passing through Earth's orbital plane

What conditions must exist for a solar eclipse to occur? Select all that apply.

-it must be new moon -the Moon must be passing through Earth's orbital plane

The Sun reaches the zenith (directly overhead) at midday ___________.

-on the equator only on the March and September equinoxes -everywhere within the tropics (between latitudes 23.5°N and 23.5°S) on two dates each year

Observations of stellar parallax therfore provide direct evidence that:

-some stars are more distant than others -Earth orbits the Sun

Use the procedure shown in the video to determine the approximate rise, highest point, and set times for different phases of the Moon, then complete the following sentences.

A new moon rises at about sunrise, reaches its highest point in the sky at about noon, and sets around sunset.

Use the procedure shown in the video to determine the approximate rise, highest point, and set times for different phases of the Moon, then complete the following sentences.

A waning gibbous moon rises at about 9pm, reaches its highest point in the sky at about 3am, and sets around 9am.

Use the procedure shown in the video to determine the approximate rise, highest point, and set times for different phases of the Moon, then complete the following sentences.

A waxing crescent moon rises at about 9am, reaches its highest point in the sky at about 3pm, and sets around 9pm.

Use the procedure shown in the video to determine the approximate rise, highest point, and set times for different phases of the Moon, then complete the following sentences.

A waxing gibbous moon rises at about 3pm, reaches its highest point in the sky at about 9pm, and sets around 3am.

The choices below are for the following question. For each question, choose the letter for the real motion that is responsible for the apparent motion as seen from Earth. A. Earth rotates once each day. B. Earth revolves around the Sun once each year. C. The direction of Earth's axis in space precesses with a period of 26,000 years. D. Stars appear to move randomly in the local solar neighborhood. E. The universe is expanding. The Moon rises in the east and sets in the west.

A: Earth rotates once each day.

When is the next opportunity to see a total solar eclipse in the United States?

April 8, 2024

Drag words from the left to the blanks at the right to complete the sentence correctly.

At most times, Mars appears to move eastward relative to the stars. The exceptions are during its periods of apparent retrograde motion, when Mars appears to move westward relative to the stars.

The choices below are for the following question. For each question, choose the letter for the real motion that is responsible for the apparent motion as seen from Earth. A. Earth rotates once each day. B. Earth revolves around the Sun once each year. C. The direction of Earth's axis in space precesses with a period of 26,000 years. D. The universe is expanding. No one on Earth can see the constellation Orion in June.

B: Earth revolves around the Sun once each year.

Complete the sentence correctly by dragging a word representing Mars's appearance to the first blank and a time of day to the second blank.

Consider a time when Mars is in the middle of one of its periods of apparent retrograde motion. During this time, Mars appears brightest in our night sky and crosses the meridian around midnight.

Roughly what time of day is a Third Quarter Moon highest in the sky?

Dawn

Suppose the moon's orbital position is located as shown in the figure below. At what time will the moon be highest in the sky?

Dusk

When we see Saturn going through a period of apparent retrograde motion, it means

Earth is passing Saturn in its orbit, with both planets on the same side of the Sun.

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.

The Sun rises and sets each day because

Earth rotates once each day

What is the basic reason that we have seasons on Earth?

Earth's axis is tilted relative to the ecliptic plane.

While an observer on Earth sees a total solar eclipse, an astronaut is on the near side of the Moon. What would the astronaut see?

Earth's day side with a dark spot moving across it.

As you saw in Part D, stellar parallax exists only because Earth orbits the Sun. Therefore, if the ancient Greeks had measured stellar parallax, they would have known that their belief in an Earth-centered universe was wrong. Why didn't the ancient Greeks measure stellar parallax?

Even for the nearest stars, parallax angles are too small to measure with the naked eye.

Where does the Sun remain above the horizon all day (never setting) on the December solstice?

Everywhere between the Antarctic Circle (latitude 66.5°S) and the South Pole

Complete the sentence correctly by dragging words representing something you can measure to the first blank and a time period to the second blank.

If you wanted to document the apparent retrograde motion of Mars, you would need to measure and record Mars's position among the constellations over a period of several months.

The following figures show a top view of Earth, sunlight, and six different positions of the Moon as it orbits Earth. Note that the distances shown are not drawn to scale. Rank each of the six lunar positions based on the amount of the Moon's total surface that is illuminated by sunlight. If two (or more) diagrams have an equal amount of surface illuminated by sunlight, put one on top of the other. (Assume that conditions for an eclipse are not met in any of these diagrams.)

Exactly half of the Moon's surface is illuminated by sunlight at all times. However, as you will see in Part B, the amount of the illuminated face that we see from Earth varies with the Moon's orbital position.

When is the Sun in the Northern part of the sky at noon for people who live on the equator?

From March 21 until Sep. 21

Which photo shows what the Moon looks like when it is in the position shown in the following moon phase diagram?

Full moon

Listed following are locations and times at which different phases of the Moon are visible from Earth's Northern Hemisphere. Match these to the appropriate moon phase.

Full moon -occurs 14 days after the new moon -rises at about the time the Sun sets -visible due south at midnight

Match the correct names for regions of eclipse shadows to their descriptions. Drag words from the left to the blanks in the sentences at the right.

Full shadow (umbra): the dark, central region of an object's shadow, in which light from the Sun is fully blocked

On your way to work about two hours after sunrise, you notice the moon setting. What phase is it in?

Gibbous

A couple hours before sunrise, the Moon appears near the western horizon as shown below in the View from Earth window. Which of the orbital positions marked by letters best corresponds to the orbital position of the Moon?

H

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.

The combination of the 173-day period between eclipse seaons and the Moon's approximately 29 1/2 - day cycle of phases leads to what we call the saros cycle, which lasts about 18 years, 11 1/3 days. Which of the following accurately describe something about the saros cycle?

If there is a solar eclipse in your home town today, there will be a solar eclipse in a different part of the world 18 years, 11 1/3 days from now.

What happens to Earth's axis as we orbit around the Sun over the course of each year?

It remains pointed in the same direction at all times.

What is special about the June solstice?

It's the day on which the Northern Hemisphere receives its most direct sunlight.

Which of the following planets has essentially no seasons at all?

Jupiter (axis tilt = 3.1°)

Sort each item into the correct bin based on whether it describes lunar eclipses or solar eclipses.

Lunar eclipse -occurs when the Moon is on the direct opposite side of Earth from the Sun -can be seen by anyone on Earth's night side at the time -occurs when Earth's shadow falls on the Moon -can occur only at full moon

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°)

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.

Consider again the portion of the video discussed in Part A. Notice that in the view through the cameara, the parallax is larger (the apparent movement is larger) for the man than for the trees, and that the mountains do not appear to shift at all. Why?

The amount of parallax depends on an object's distance, with larger parallax for nearer objects.

Suppose you see a first quarter moon in your evening sky. How will the Moon's appearance change over the next few days?

The moon will rise a little later each day, and with each passing day you will see a little more of the Moon's face illuminated.

How would a star's parallax change as its distance from Earth increases?

The parallax shift decreases as the star's distance from Earth increases.

Beginning about 55 seconds into the video, you'll see an animation of a photographer looking through her camera at a man, a set of trees, and distant mountains. Notice that, as viewed through the camera, the positions of the man and the trees change (relative to distant mountains) as the photographer moves. Which of the following statements correctly describes what is really happening in this situation?

The photographer is moving, but the man and the trees are staying still.

Which of the following best describes why we have seasons on Earth?

The tilt of Earth's axis causes different portions of Earth to receive more or less direct sunlight at different times of year.

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.

Do you think Northern Hemisphere summers are warmer or colder than Southern Hemisphere summers on Mars?

They are colder.

Do you think Northern Hemisphere winters are warmer or colder than Southern Hemisphere winters on Mars?

They are warmer.

Two observers, one in northern Canada and the other in Australia, are looking at the Moon on the same day. The observer in Canada sees a Third Quarter Moon. What does the observer in Australia see?

Third Quarter Moon

Which of the following planets should have the most extreme seasons?

Uranus (axis tilt = 97.9°)

Listed following are locations and times at which different phases of the Moon are visible from Earth's Northern Hemisphere. Match these to the appropriate moon phase.

Waning crescent moon -occurs about 3 days before new moon -visible near eastern horizon just before sunrise

Suppose you look up in the sky and the Moon appears as in the photo below. Which of the following diagrams correctly shows the Moon's location in its orbit around Earth for this phase?

Waning gibbous

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 moon

Listed following are locations and times at which different phases of the Moon are visible from Earth's Northern Hemisphere. Match these to the appropriate moon phase.

Waxing crescent moon -sets 2-3 hours after the Sun sets -visible near western horizon about an hour after sunset

Just as you found for parallax on Earth, stellar parallax is larger for stars that are nearer and smaller for stars that ar more distant. Which statement best summarizes why stellar parallax occurs? You may find it helpful to watch the animation of stellar parallax that begins at about 1:20 into the video.

We view nearby stars from different positions in Earth's orbit at different times of year.

When is the Sun highest in the sky at noon for people living in Sydney, Australia?

Winter solstice (Dec. 21)

We cannot see a new moon in our sky because _________.

a new moon is quite near the Sun in the sky

What is an annular eclipse?

a solar eclipse in which the Moon does not appear large enough to fully block the Sun

As discussed in the video, parallax measurements allow us to calculate distances to stars for which parallax is detectable. Suppose you have a telescope capable of measuring parallax shifts of a particular amount (for example, 0.001 arcsecond). Which of the following locations for the telescope would allow you to measure distances to the most distant stars?

a telescope on Mars

Eclipse seasons do not occur exactly twice a year. Instead, they occur slightly more often, coming about 173 days apart (which is a bit less than the roughly 182 to 183 days that make up 6 months). Why do they do this, rather than occurring exactly twice each year?

because the line of nodes gradually moves around the Moon's orbit

Stars that are visible in the local sky on any clear night of the year, at any time of the night, are called _________.

circumpolar

If the Earth did not have a tilt, the weather during June in Colorado would be ____________.

colder

If the Earth were tilted 45 degrees (rather than 23.5 degrees), winters in Colorado would be ____________.

colder

As seen from Earth, the Sun appears to follow the annual path that we call the __________ around the celestial sphere.

ecliptic

Based on their inability to detect stellar parallax, the ancient Greeks concluded that _________.

either Earth is the center of the universe or stars are extremely far away

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

Suppose you see a moon that is half bright and half dark in your early evening sky. Then you are seeing a __________ moon.

first quarter

Lunar eclipses can occur only during a _________.

full moon

Suppose you live at a mid-latitude in the Southern Hemisphere (such as in Australia, New Zealand, Chile, or South Africa). When will you have 12 hours of daylight and 12 hours of darkness?

on both the March and September equinoxes

If the Moon's orbit were not tilted with respect to the ecliptic, solar eclipses would occur ____________.

once a month

During the time that a planet is in its period of apparent retrograde motion, _________.

over many days or weeks, the planet moves westward relative to the stars, rather than the usual eastward relative to the stars

The final step is to determine the rise and set times for this phase. Which of the following are the correct times for a third quarter moon?

rise: about midnight; set: about noon

The fact that we always see the same face of the Moon tells us that the Moon

rotates with the same period that it orbits Earth.

About what time is it for the person who sees the third quarter moon at its highest point (position 4 in the diagram from Part B)?

sunrise

If the Earth were tilted 90 degrees (rather than 23.5 degrees), summer in the Arctic would be ____________ summer in Colorado.

warmer than

Beijing and Philadelphia have about the same latitude but very different longitudes. Therefore, tonight's night sky in these two places:

will look about the same.

When it is summer in Australia, the season in the United States is

winter.