MasteringAstronomy Assignment #1

Sorting Task: Testable and Not Testable by Science
Part A
Listed following are a series of statements that each make a claim. Classify these as either testable by accepted methods of science or non-testable by accepted methods of science. Be sure to note that this question does not ask whether a statement would pass or fail a test; it only asks whether it is testable in principle.

Ranking Task: Altitude of a Star
Part A
Listed following are the latitudes of several locations on Earth. Rank these latitudes from left to right based on the maximum altitude (on the meridian) at which the celestial equator passes through the local sky, from lowest altitude (nearest the horizon) to highest altitude (farthest above the horizon).

Part B

Listed following are the latitudes of several locations on Earth. Rank these latitudes from left to right based on the maximum altitude (on the meridian) at which you would see a star with a declination of 0°, from lowest altitude (nearest the horizon) to highest altitude (farthest above the horizon).

Part C

Listed following are the declinations of five different stars. Rank these declinations from left to right based on the maximum altitude (on the meridian) each star reaches for an observer at latitude 60°N, from lowest altitude (nearest the horizon) to highest altitude (farthest above the horizon).

Ranking Task: Lunar Phases II

Part A

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 from left to right based on the amount of the Moon’s illuminated surface that is visible from Earth, from greatest to least. (If two diagrams have an equal amount of illumination as seen from Earth, put one on top of the other.)

Part B

Shown following are five different phases of the Moon as seen by an observer in the Northern Hemisphere. Imagine that tonight the Moon is in the waxing gibbous phase (as shown at the far left (labeled “first”) in the following ranking box). Rank the pictured phases from left to right based on the order in which you would see them over the next four weeks, from first seen to last.

Visual Activity: Conditions for Eclipses

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. (Click “Show Moon with flat orbit” to see this situation.) 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

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.

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.

If you could change the layout of the solar system, which of the following would cause a lunar eclipse to occur at least once every month in this hypothetical situation?

Change the Moon’s orbital plane so it is in the same plane as Earth’s orbit around the Sun.

Sorting Task: Phases of the 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.

Process of Science: Geometric Distance Measurements

Part A

Geometric reasoning can be used to measure distances both on Earth and in space. Surveyors on Earth and astronomers both use the geometric technique of triangulation to determine the distances and sizes of remote objects. In order to determine the distance using the triangulation method, a few key geometric components must be known. Once the baseline and the sightline angles are determined, then the distance can be calculated with simple geometric reasoning.

In the figure below, label the essential components used to triangulate the distance to the tree located on the opposite side of the river.

Part B

Use the figure to determine how the measured parallax changes in each of the following situations:

Match the words in the left column to the appropriate blanks in the sentences on the right. Make certain each sentence is complete before submitting your answer.

Part C

Consider the Moon and Sun. Their angular diameters are both equal to about .5 degree. If the Sun is roughly 400 times more distant than the Moon, how much bigger is the Sun’s diameter than the Moon’s?

about 400 times bigger

Sorting Task: Solstices and Equinoxes

Part A

Listed following are observable characteristics of equinoxes and solstices in the continental United States (which means temperate latitudes in the Northern Hemisphere). Match each characteristic to the corresponding equinox or solstice.

Ranking Task: Sidereal and Synodic Periods 

Part A

Each item following represents an amount of time. Recall from your reading that “sidereal” refers to events that are timed with respect to the distant stars, and “synodic” refers to special alignments of astronomical bodies, such as the Earth, Moon, and Sun. Rank the items from left to right in order of the amount of time they represent, from shortest time to longest time. If two items represent equal amounts of time, show this equality by dragging one on top of the other.

Vocabulary in Context: Describing Eclipses of the Sun and Moon

Part A

Match the words in the left-hand column to the appropriate blank in the sentences in the right-hand column. Use each word only once.

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A long, thin cloud that stretched from directly overhead to the western horizon would have an angular size of

90º

When a thin crescent of the Moon is visible just before sunrise, the Moon is in its

waning phase

If the Moon's orbit were a little larger, solar eclipses would be

more likely to be annular

In Figure 1.28 in the textbook ("Triangulation"), using a longer baseline would result in

a smaller angle at point B

What would the measured angle in Discovery 0-1 have been if Earth's circumference were 100000 km instead of 40000 km? (Express your answer using two significant figures.)
Angle = 2.8 degrees

What angle would Eratosthenes have measured had Earth been flat?
0 degrees

What is precession, and what causes it?
Answer Key: Discovered by the Greek astronomer Hipparchus, precession is a slow shift in the orientation of the Earth's axis of spin. Although Earth's axis maintains an axis tilt of 23.5 degrees compared to the axis of the Sun, the axis moves in a circle over the course of 26 000 years. This causes the location of the celestial poles to shift, along with the entire sky. It is caused by the gravitational influence of the Moon and Sun.

Like latitude on Earth, ________ in the sky is measured in degrees north and south of the equator.
declination

The time interval of 365.242 days is defined as the ________.
tropical year

The apparent annual path the Sun takes through the sky is called the ________.
ecliptic

One of the requirements of the Scientific Method is that an experiment must be ________.
repeatable

The star Wolf 1061 has a parallax of 2.34 arcseconds, while the star Ross 652 has a parallax of 1.70 arcseconds. What can you correctly conclude?
Wolf 1061 is closer to Earth than Ross 652.

The synodic month is
29.5 days.

A solar eclipse can only happen during a:
new moon.

The fact that the Earth has moved along its orbit in the time it took to rotate once is the reason for
the difference between solar and sidereal time.

In general, what is true of the alpha star in a constellation?
It is the brightest star in the constellation.

The south celestial pole is located at a declination of -90 degrees.
True