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Astronomy, section 1, Fall 2019
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Seeds et al - Astro 4/e (Homework)

James Finch

Astronomy, section 1, Fall 2019

Instructor: Dr. Friendly

Current Score : 1 / 48

Due : Monday, January 28, 2030 00:00 EST

Last Saved : n/a Saving... ()

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Question

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1/48 (2.1%)

Instructions

In this Sample Assignment, you will see several of the question types found in Astronomy, 4th edition, by Michael A. Seeds, Dana Backman, and Eric Wegryn and published by Cengage Learning.

Many of these question types provide scaffolding to build skills and confidence in the use of simple algebra, geometry, and proportional reasoning to solve astronomy problems. Many provide targeted feedback to address specific student errors. Finally, the Virtual Astronomy Laboratories provide rich interaction elements—samples from two different VALs appear at the end of this sample assignment. This demo assignment allows many submissions and allows you to try another version of the same question for practice wherever the problem has randomized values.

The answer key and solutions will display after the first submission for demonstration purposes. Instructors can configure these to display after the due date or after a specified number of submissions.

Assignment Submission

For this assignment, you submit answers by question parts. The number of submissions remaining for each question part only changes if you submit or change the answer.

Assignment Scoring

Your last submission is used for your score.

1. –/2 points Astro4 2.DIG.OP.004. My Notes

This is an Optimized Problem. Optimized Problems offer randomized parameters and provide immediate feedback to students who have incorrectly answered any part of the problem. Try putting in an incorrect answer to see an example of this just-in-time assistance.

If you are at latitude 47 degrees north of Earth's equator, what is the angular distance (in degrees) from your zenith to the north celestial pole?

What is the shortest angular distance (in degrees) from your nadir to the north celestial pole?

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2. –/15 points Astro4 13.DIG.Ord.001. My Notes

This is a Sense-of-Proportion question. These are brief ranking/analytical questions that help students comprehend the breadth of different proportionalities that exists within Astronomy.

Answer the questions below.

An H-R diagram is shown with the names of specific stars plotted. This diagram has 4 axis labels, one on each side of the plot.

The bottom horizontal axis is labeled Temperature (K) and it begins at 40,000 K on the left to 1000 K on the right.

The top horizontal axis is labeled "Spectral type" and is sectioned at certain intervals. The region between 40,000 kelvin and around 30,000 kelvin is labeled O. The region between 30,000 kelvin and 10,000 kelvin is labeled B. The region between 10,000 kelvin and 8000 kelvin is labeled A. The region between 8000 kelvin and 6000 kelvin is labeled F. The region between 6000 kelvin and 4500 kelvin is labeled G. The region between 4500 kelvin and 3500 kelvin is labeled K. The region between 3500 kelvin and 1000 kelvin is labeled M.

The vertical axis on the left is labeled Luminosity in *L/L*_Sun. It ranges from 10⁻⁵ at the bottom and ends at 10⁶ at the top.

The vertical axis on the right is labeled Absolute Magnitude in M_V and it ranges from 15 at the bottom to -10 at the top.

The Main sequence of the stars enters the viewing window from the left at 10^5.5 *L/L*_Sun and moves down and to the right at a constant slope until it approaches 3300 K, where it takes a sharp drop until it exits the viewing window. The Red dwarfs occupy the bottom of the Main sequence. Supergiants occupy a broad region at Luminosities above 10⁴ *L/L*_Sun in the upper left and upper right regions of the diagram above the Main sequence. The Giants occupy a broad region to the right of and above the Main sequence but lower than the supergiants. The white dwarfs occupy a broad region below the Main sequence.

Parallel, diagonal dashed lines are present on the diagram to indicate the radii of the stars. The 0.01 R_Sun line cuts across the region of white dwarfs. The 0.1 R_Sun line cuts across the region of red dwarfs. The 1 R_Sun line runs through the lower part of the Main sequence. The Sun is on this line. The 10 R_Sun line cuts across the very top of the Main sequence and through the lower left region of Giants. The 100 R_Sun line cuts through the central region of Supergiants and the top right region of Giants. The 1000 R_Sun line cuts through the right region of Supergiants.

(a) Rank the following stars from the above H-R diagram in order of brightness from dimmest to brightest: Barnard's Star, Canopus, Rigel A, Sirius B, Sun.

dimmest



brightest

(b) Rank the following stars from the above H-R diagram in order of brightness from brightest to dimmest: Aldebaran A, Altair, Antares, Polaris, Procyon B.

brightest



dimmest

(c) Rank the following stars from the above H-R diagram in order of temperature from hottest to coolest: Aldebaran A, Altair, Antares, Mira, Rigel A.

hottest



coolest

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3. –/1 points Astro4 13.DIG.P.004. My Notes

This is a General Problem. General Problems are multiple-select items, in which several choices may be correct. They invite students to synthesize descriptive knowledge about a particular topic.

Based on what you know about the masses of stars, select all of the correct statements from the following list.

Some stars are thinner than air. All stars follow the mass-luminosity relation. Giant and supergiant stars tend to be dense. Direct determination of mass can only be done for stars in binary systems. Most main sequence stars are of similar mass to the sun. White dwarf stars are very dense. Brighter main sequence stars are more massive.

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4. 0/5 points | Previous Answers Astro4 21.LI.Tut.005. My Notes

This is a Tutorial. Tutorials coach the student through every step of the most essential astronomical problems. These highly structured, scaffolded learning activities give strong support to the student with emerging or dormant quantitative-reasoning skills.

What is the angular separation (in arc seconds) of the Sun and Jupiter if observed from Luyten 726-8B at a distance of 2.7 pc? (Assume Jupiter is located 5.2 AU from the Sun.)

What diameter telescope (in m) would you need to resolve the separation between the Sun and Jupiter at a wavelength of 550 nm?

What would the apparent magnitude of the Sun be from this distance

(M = 4.8)?

A horizontal coordinate line labeled "Apparent magnitude (m_V)" ranges from −30 on the left to 30 on the right. Arrows indicate that values to the left are brighter and values to the right are fainter. The following points are labeled on the line:

Sun at −27

Full moon at −12

Venus at brightest at −4

Sirius at −1

Polaris at 2

Naked eye limit at 6

*Hubble Space Telescope* limit at 30

Is the Sun visible with the naked eye at this distance?

To calculate the angular size, we use the small angle formula:

2.06 ✕ 10⁵

We first need to convert the distance between the Sun and Jupiter into parsecs.

d_pc

d_AU

1 pc

2.06 ✕ 10⁵ AU

d_pc

2.52e-05

How many AU are in a parsec? pc

Now solving the small angle formula for the angular separation (in arc seconds):

θ =

2.06 ✕ 10⁵

d_pc

D_pc

θ =

1.93

Use the small angle formula to calculate the angular size from separation and distance given. arc seconds

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5. –/1 points Astro4 3.DIG.P.043. My Notes

This is a Review Question. Generally adapted from the textbook, Review Questions provide opportunities for test prep and formative assessment.

You are located in Tuscaloosa, AL, United States. Your friend is located in Rio de Janeiro, Brazil. You see a waning gibbous in your clear night sky. What phase, if any, will your friend see if the night sky in Rio de Janeiro is also clear?

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6. –/6 points Astro4 VAL.4.002. My Notes

This is part of a Virtual Astronomy Laboratory (VAL). Each can be assigned as a standalone activity or as part of a larger learning experience. VALs incorporate real astronomical data, simulations, and other interactive elements to offer students the opportunity to experience astronomy in an authentic manner. Targeted feedback guides students in revising any incorrect answers.

The Earth's Magnetic Field

The photo below shows an auroral display seen from Landmannarlaugar, Iceland. Many aurora-seekers travel to Iceland because the island nation is so close to the Earth's north magnetic pole. Magnetic-field lines converge there, concentrating the flow of charged particles and boosting the odds of seeing the Northern Lights.

But that's not the only benefit of Earth having a strong, well-ordered magnetic field. Because magnetic fields exert forces upon moving charges, we on Earth are largely shielded from the solar wind—especially intense during solar storms—and from rare but high-powered cosmic rays: atomic nuclei hurtling across space from sources such as supernova explosions and black holes. This shielding greatly reduces the risks of radiation damage and mutation in terrestrial life forms.

In this section we'll learn about the forces that allow magnetic fields to shape the aurorae while shielding the Earth from hazardous particles.

A photograph of an auroral display seen from Landmannarlaugar, Iceland.

A Protective Barrier ▲

The Earth's magnetic field exerts forces on moving charged particles, and this shields nearly all of the Earth's surface from the solar wind and from cosmic rays.

The Earth has a powerful magnetic field because currents of iron-nickel alloy are circulating in its liquid core. When the electrically charged particles of the solar wind encounter the Earth's magnetic field, they experience a force called the Lorentz force.

In a nutshell, charged particles in a magnetic field experience a force that is perpendicular to both the direction of the field and the direction of the particles' motion.

The strength of the force depends on the amount of electric charge, how fast the charges are moving, and the strength of the magnetic field. Particles that have no charge do not experience this force. Nor do particles that are stationary, regardless of whether or not they are charged.

The following activity allows us to explore the nature of this unusual but essential force—a force that operates in toys, cars, power tools, and anything else with an electric motor.

An illustration of the magnetic field of the Earth. Field lines emanate from the south magnetic pole and converge at the north magnetic pole.

This conceptual illustration shows selected magnetic-field lines emanating from one magnetic pole and converging on the other. This dipole field pattern is similar to that of a simple bar magnet.

Assessment: Magnetic Forces

Magnetic Forces

The Magnetic Forces simulation allows us to explore the effects that magnetic fields have on moving charged particles. Note that you can change the direction of the magnetic field and the type of particles entering the magnetized region, both by using radio buttons near the bottom of the frame. in addition, sliders allow you to modify the magnetic field strength and the particle energy (related to speed). Note that you can adjust the sliders by using your keyboard's left and right arrow keys, but first you must click on the dot at the end of the slider you wish to manipulate.

Take a minute to familiarize yourself with the functions of the simulation. Then conduct the exercises that appear below.

Use the Magnetic Force simulation to complete the table below. For Particle Deflection Direction, indicate whether the particles move left, right, or neither (undeflected). Feel free to adjust the magnetic field strength or particle energy to make the effects easier to study. (For example, electrons feel magnetic forces much more strongly than do protons, since they have equal amounts of charge—sign aside—but very different masses.)

Particle Type	Magnetic Field Direction	Particle Deflection Direction
Protons	Into Screen
Protons	Out of Screen
Electrons	Into Screen
Electrons	Out of Screen
Neutrons	Into Screen
Neutrons	Out of Screen

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7. –/12 points Astro4 VAL.20.STEL.002. My Notes

Stellarium Activities engage students in exploring the night sky through realistic, interactive online learning. These immersive activities cover constellations, planets, stellar properties, and more, using diverse assessments to enhance critical thinking and expand celestial knowledge.

Seasonal Constellations

Depending on where you live, you likely have several stars and constellations that you can always see. Can you think of any offhand? It's interesting to think that no matter the month, no matter what time (as long as it's dark out), you will always be able to see these certain patterns in the night sky. Constellations that are always up above the horizon are called circumpolar constellations. The night sky navigation activity reviews those circumpolar constellations.

On the other hand, there are constellations that are more fleeting. It's possible that you could see certain constellations in the winter, but by the time spring and summer roll around, they are no longer visible no matter when you look. These are called seasonal constellations.

We'll set out to identify what determines circumpolar and seasonal constellations.

Step 1: Seasonal Constellation Identification

Open Stellarium. Once it's loaded, press the "K" key to stop the forward motion of time. Next, press F6 to set your location. Search for Detroit, Michigan (shown as "Detroit, Northern America") and click on it. You're now seeing the sky as it would appear from Detroit. Press F5 and set the time to 11 p.m. (23:0:0) and the date for January 15, 2023 (2023-1-15). The sky should be dark. Now press the "C" key to bring up the constellation lines and the "V" key to bring up the constellation names. Navigate to the Northern part of the sky. If you are looking Northward, your view should look something like this.

Ursa Minor, and portions of Cepheus, Draco, and Ursa Major as displayed in Stellarium. †Screenshot from Stellarium Software
A star chart which includes the constellations Cepheus, Ursa Minor, and Draco.

From Detroit, Michigan, Ursa Minor is a circumpolar constellation, which is a constellation that always remains above the horizon for an observer located at a certain Earth latitude. Ursa Major, Cassiopeia, Draco, and Cepheus, which are all relatively close to Ursa Minor, are also circumpolar constellations when viewed from Detroit, Michigan.

In Stellarium, navigate to the Southern sky. If you are looking towards the South, your view should look something like this.

Canis Major, Lepus, and portions of Orion and several other constellations as displayed in Stellarium. †Screenshot from Stellarium Software
A star chart shows several constellations. The constellations Canis Major and Lepus are fully displayed and oriented near the center of the chart. Partially displayed constellations include Pyxis, Puppis, Columba, and Eridanus. The stars Rigel and Sirius are labeled.

From the list below, select all the constellations that are above the horizon and visible at 11 p.m. on this date.

As you might have guessed, it is winter in the Northern Hemisphere on January 15th, and the constellations you just identified are winter constellations for the Northern Hemisphere. Constellations that are above the horizon and visible only at certain times of the year are referred to as seasonal constellations. Six months later, in June, Detroit's summer seasonal constellations will be visible above the horizon at night, and the winter seasonal constellations you just identified will all be below the horizon. You can see for yourself by advancing forward in time to June 15th of the same year while keeping the time set to 11 p.m. Notice how all of all the constellations you just identified are below the horizon.

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8. 1/6 points | Previous Answers Astro4 3.3.DWB.001. My Notes

Digital Workbook questions interweave narrative and interactives of a variety of media types with assessments, containing an introduction to the relevant topics and subtopics.

Part 1—What causes the Moon's phases?

1A) What are the Moon's phases?

1B) How do sunlight and the Moon's orbit cause the Moon's phases?

Part 2—How does the Moon always face the same side toward Earth?

2A) What are the features on the Moon's visible side?

2B) What does it mean that the Moon has synchronous rotation?

Part 1 of 4 - 1A) What are the Moon's phases?

Part 1—What causes the Moon's phases?

A series image shows the changing visibility of the the Moon's surface during its phase cycle.

The changing phasessequence of changing appearance of the Moon in terms of what part is brightly lit compared with what part is unlit, dark of the Moon during a month (figure above) is one of the most easily observed phenomena in astronomy.

Starting this evening, begin looking for the Moon in the evening sky. You might have to wait for almost a month before you find it appearing at a convenient time, but then, as you continue to watch the Moon night by night, you will see it passing through its cycle of phases. (Note that a lunar monththe time for the Moon to go through a complete phase cycle, 29.5 days, also called a 'synodic' month, the time for the Moon to go through a complete phase cycle, is 29.5 days, slightly shorter than a calendar month.)

Try this Moon phase calculator.

What's the Moon's phase tonight?

(No Response)

Key: Answers may vary.

This answer has not been graded yet.

What was the Moon's phase on the day you were born?

(No Response)

Key: Answers may vary.

This answer has not been graded yet.

Sometimes people are surprised to see the Moon in the daytime sky, and they think something has gone wrong. No, nothing is wrong. The Moon is usually visible in the daytime in its "waning gibbous" phase (just past full; look again at the figure above). Quarter and crescent moons can also be visible in the daytime sky but are harder to see when the Sun is above the horizon and the sky is bright.

Part 2 of 4 - 1B) How do sunlight and the Moon's orbit cause the Moon's phases?

An illustration shows the Earth (drawn as a cross-section) at the center of the Moon's circular orbit. The illustration is oriented such that the Earth has counterclockwise rotation about its axis, which is perpendicular to the page and labeled "North Pole." The Moon's orbit, labeled "Moon's monthly revolution," is observed from a distant point along the Earth's axis. Sunlight is incident from the right side of the illustration and phases of the the Moon are indicated at equidistant intervals along its orbit as follows. In each case, the right half of the moon (the half facing the sunlight) is illuminated.

New moon: The Moon is drawn directly to the right of the Earth's right edge. The time of day for a person drawn on the right edge of the Earth is labeled "Noon."

Waxing crescent: The Moon is drawn above the Earth's top edge and to the right.

First quarter: The Moon is drawn directly above the Earth's top edge. The time of day for a person drawn on the top edge of the Earth is labeled "Sunset."

Waxing gibbous: The Moon is drawn above the Earth's top edge and to the left.

Full moon: The Moon is drawn directly to the left of the Earth's left edge. The time of day for a person drawn on the left edge of the Earth is labeled "Midnight."

Waning gibbous: The Moon is drawn below the Earth's bottom edge and to the left.

Third quarter: The Moon is drawn directly below the Earth's bottom edge. The time of day for a person drawn on the bottom edge of the Earth is labeled "Sunrise."

Waning crescent: The Moon is drawn below the Earth's bottom edge and to the right.

The Moon orbits counterclockwise around Earth as seen from above Earth's North Pole (figure above). As a result, an observer on Earth sees the Moon move relative to the background of the constellations. If you watch the Moon for just an hour, you can see it move eastward by slightly more than its own apparent diameter. Each night the Moon is about 13 degrees eastward of its location the night before, more than the width of the Big Dipper's bowl.

Bottom line: The changing phases of the Moon are caused by sunlight illuminating different portions of the Moon as the Moon orbits Earth.

Run the animation and see how the motion of the Moon in its orbit causes its phase cycle.

The phases of the Moon are caused by which of the following?

the Moon's orbital motion around Earth the Sun's shadow the Earth shadow the Moon's orbital motion around the Sun

✓ CORRECT. As the Moon orbits Earth, we see different parts of the Moon lit by sunlight, causing the different phases.

Part 2—How does the Moon always face the same side toward Earth?

A photograph of a full moon is shown with several surface features labeled.

The image above is a photo of a full moon with labels added for the dark markings that make up the "Man in the Moon" (Western cultures) or "Rabbit in the Moon" (Eastern cultures). The first astronomers who used telescopes thought they were looking at bodies of water, and gave the dark areas names such as the Sea of Tranquility (in Latin, Mare Tranquillitatis, pron. Mah-ray Tran-kwill-ih-tah-tiss, at right-center in the image). These are actually smooth plains made by lava that flowed across the Moon's surface and cooled long ago.

Where have you heard the name "Sea of Tranquility" before?

This answer has not been graded yet.

Carefully compare the labeled full moon image above with this montage of images showing the Moon's phase cycle, repeated from the start of this lesson.

Notice that the same "seas" and other surface features stay constantly in the same locations, although sometimes they are unlit and invisible. You have discovered, or been reminded, that the Moon always keeps the same side facing us on Earth.

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WebAssign

Welcome, demo@demo

Seeds et al - Astro 4/e (Homework)

Current Score : 1 / 48

Due : Monday, January 28, 2030 00:00 EST

Last Saved : n/a Saving... ()

Instructions

Assignment Submission

Assignment Scoring

The Earth's Magnetic Field

Magnetic Forces

Seasonal Constellations

Step 1: Seasonal Constellation Identification

Table of Contents

Part 1—What causes the Moon's phases?

Part 2—How does the Moon always face the same side toward Earth?

Part 1—What causes the Moon's phases?

Part 2—How does the Moon always face the same side toward Earth?