at the end of each chapter in your textbook there are ... 2, implications of the earth’s and...

At the end of each chapter in your textbook there are lists of problems. None of these are assigned to you to write out. However, they are useful for you to review your reading and to be sure that you understand the chapter. Below are listed the problems from each chapter that concern the topics we will be discussing, however briefly, in class. Use them to review the material, if you wish.

The following “problems” are for those of you who are reading Edition 3 of the textbook. If you are reading Edition 4, 5, 6, or 7, look on the next slides for the “review questions” that apply.

Chapter 1, 3rd Edition, “Problems”:

11, 13, 14, 15; rest covered by your lab on astronomical distances.

Chapter 2, 3rd Edition, “Problems”: 11-14, 16-19, and 20-22 are optional.

Chapter 3, 3rd Edition, “Problems”: 12-16

Chapter S1, 3rd Edition, “Problems”: 19, 20, 22a-d, 24

Chapter 5, 3rd Edition, “Problems”: 10, 12-15, 17-20; the rest are fun but you don’t need to be able to do them.

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The following “review questions” are for those of you who are reading Edition 4 of the textbook. If you are reading Edition 5, look on the next slide for the “problems” that apply.

Chapter 1, 4th Edition, “Problems”:

11, 15, 16, 17, 18, 22; rest covered by your lab on astronomical distances.

Chapter 2, 4th Edition, “Review Questions”: 3-10, 12-16.

Chapter 3, 4th Edition, “Review Questions”: 7-14.

Chapter S1, 4th Edition, “Review Questions”: 7, 9, 10.

Chapter 5, 4th Edition, “Review Questions”: 2, 7, 8, 12, 14-18.

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The following “review questions” are for those of you who are reading Edition 5 of the “Essential Cosmic Perspective.”

Chapter 1, 5th Essential Edition, “Review Questions”:

1, 11; rest covered by your lab on astronomical distances.

Chapter 2, 5th Essential Edition, “Review Questions”: 3-5, 9, 10, 12-16.

Chapter 3, 5th Essential Edition, “Review Questions”: 6-12.

Chapter 4, 5th Essential Edition, “Review Questions”: 2, 3, 6-11, 13, 15.

Chapter 5, 5th Essential Edition, “Review Questions”: 1, 3, 4, 8-12, 15, 16.

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Chapter 1, 6th Essential Edition, “Review Questions”: 1, 5, 6.

Chapter 2, 6th Essential Edition, “Review Questions”: 1, 3-5, 8-10, 12, 14-16.


Chapter 4, 6th Essential Edition, “Review Questions”: 5-11, 13, 15, 16.

Chapter 5, 6th Essential Edition, “Review Questions”: 1-4, 8-11, 12, 15, 16.

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Chapter 1, 7th Essential Edition, “Review Questions”: 2, 3, 9.The other questions refer to material we will cover in class only later.

Chapter 2, 7th Essential Edition, “Review Questions”: 1, 3-5, 8-10, 12, 14-16.


Chapter 4, 7th Essential Edition, “Review Questions”: 5-11, 13, 14.

Chapter 5, 7th Essential Edition, “Review Questions”: 1-4, 8-14.

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The Andromeda Galaxy (M31)

Our galaxy’s nearest big neighbor.

Chapter 1, the Vastness of the Universe:

1. light-years as distance.

2. Light connects distance and time.Examples are computers, Internet, control of Mars rover.Looking back to dawn of universe with Hubble deep field.

3. Best guess is universe is 14 billion years old.

4. Vastness of the universe means we observe, but essentially cannot converse.

a) Andromeda galaxy 100,000 light-years across and 2.5 million light-years away.

b) Newly discovered solar systems are much closer (50 to 200 light years or so), but I will be dead by the time they answer my question (like E-mail as compared to the telephone, but on a much longer time scale).

Chapter 1, Implications of the Vastness of the Universe:

5. Everything is so far away that the sky looks like a (2-D) dome.

6. Measure distances over the sky in angles,not in light-years.

7. Patterns of stars on the sky seem constant.

a. Rearrangements of star patterns take millennia.

b. Takes really high tech to measure any changes.

c. Even the orbits of exoplanets, if they are like our own Jupiter, would take years to observe for a full circuit.

d. One talks about “astronomical distances,” but “geologic times.” But times tend to be just as big in astronomy too.

8. The “fixed” stars provide a frame of reference, “the celestial sphere.”

Chapter 2, Implications of the Earth’s and Moon’s Motions:

1. Getting a feel for angles on the dome of the sky:

a. The disk of the moon or sun is about 1/2º

b. The separation of the stars in the big dipper that point to Polaris is about 5º

c. Your fist held at arm’s length subtends about 10º

2. Using your fist in the moon observing project.

a. Noting the local time (standard time or daylight time).

b. Finding the meridian by facing south.

c. Measuring distance in degrees from meridian (hour angle).

Figure 1.9Winter

TriangleChapter 2 , Implications of the Earth’s and

Moon’s Motions :

3. Orion easy to recognize (in winter).

a. Constellation as a group of bright stars.

b. Also a region of the sky, defined by the IAU in 1928.

4. Constellation names from Mediterranean area ~5000 yrs ago.

5. Southern constellations from European explorers in 17th century.

6. Don’t memorize constellations, names or locations. If Alan Sandage and Martin Schmidt didn’t know them, why should you?

7. The earth rotates, not the stars.

8. From equator, you can see everything.

9. We see less.

10. Telescopes in Hawaii and in Chile do it all.

The first direct image of the surface of another star.The Faint Object Camera of the Hubble Space Telescope observed Betelgeuse, a bright red star in

the constellation Orion. It is a red giant star, with a diameter comparable to the diameter of the orbit of Jupiter about the sun. Its great size allowed its surface to be resolved.

Size of the Star

Size of the Earth’s Orbit

Size of Jupiter’s Orbit

Figure 1.14

The apparent rotation of the celestial sphere

If you don’t believe the earth is rotating, take a time exposure.If you can find the big dipper, you can

see it appear to rotate.

If you live at the north pole, you can see only half of the sky, but it is always “up.” However, for half the year the sun blots it out with its very strong light.

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Here we see our own case, mid-latitudes in the northern hemisphere. The north celestial pole is always seen above our horizon, by an amount in degrees equal to our latitude (which, for us, is 45 degrees). As the earth rotates, everything but a small circular region around the south celestial pole is brought into view. This means that we could see all that sky each day, if there were no clouds and no sun. Clouds are temporary, but the sun’s scattered light in our atmosphere blots out everything but the sun and moon in the day-time sky. But over a year, we can see it all at night.

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Here we see the case of the equator. Both celestial poles are always located on our horizon. As the earth rotates, everything is brought into view. This means that we could see all that sky each day, if there were no clouds and no sun. Clouds are temporary, but the sun’s scattered light in our atmosphere blots out everything but the sun and moon in the day-time sky. But over a year, we can see it EVERYTHING at night if we are willing to wait until the sun moves out of the way as it makes its circuit along the ecliptic. This would seem a great place to put a telescope, but . . . .

Here is another way of looking at the same information. Now, instead of showing the earth and your horizon rotating, we show the celestial sphere (which is the sky) appearing to rotate.Some paths of stars are shown, and from this you can see that stars near the pole will always be “up,” while other stars will be up for varying lengths of time depending upon their celestial “latitudes” on the celestial sphere (and, of course, your latitude on the earth). Got it?


11. The earth is like an enormous gyroscope.a. Rotation axis nearly constant → our frame of reference.b. Defines north and south celestial poles.c. These define celestial equator.d. Meridian is great circle through poles (north-south line).e. Longitudes on celestial sphere are hard, because the earth is

rotating. (We can’t use the location of Greenwich, or any other city.)

f. Ecliptic is path of sun on celestial sphere.g. Two equinoxes are points where ecliptic crosses equator.h. This allows us to construct a coordinate system.

(You don’t need to know any more about it.)

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Figure 1.17

Depictions of latitude and longitude on

the Earth.

Celestial latitudes are the same, but longitudes are

different.

Vernalequinoxdefines zeroof celestiallongitude, notany spot on theEarth, like Greenwich.

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Here we have an earth-axis-up representation of the earth’s motion around the sun.The seasons are explained, but the orbit and the sun’s axis are tilted.

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The axis of the celestial sphere is taken as the axis of the earth, because this is so well and persistently defined naturally.The sun’s orbit, the ecliptic, is then tilted, as is also the plane of our galaxy.The vernal equinox, when the sun crosses the celestial equator (the projection to the sky of the earth’s equator), then defines the zero of a sort of celestial longitude.The earth’s spin axis does wobble, but it doesn’t wobble very much, and it takes a thousand years or so to do it.Thus the celestial coordinates are pretty well pinned down.


12. Earth revolves about sun ══►sun appears to move against the background of fixed stars.

a. Sun’s apparent path is called the ecliptic.

b. Constellations along the ecliptic are “signs of zodiac.”

c. These constellations invisible when sun is near them.

d. Hence some are summer or winter constellations.

e. Wise men (or women) have always been expected to know

1) why these heavenly motions occur,

2) how to predict them, and

3) how to divine their significance.

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A few years ago, someone pointed out that the constellations of the zodiac had moved relative to their horoscope dates, so if you thought you were a Virgo, well, maybe you were a Leo. Astrologers responded immediately that it is the date that matters and not where the sun was!

In summer, sunlight is more intense, depositing more heat energy per unit area on the ground.

In addition, there are more hours of sunlight per day in summer.

This picture was meant to illustrate something else, but it shows how the earth is illuminated by the sun at a solstice. A person at a northern latitude (left-most yellow circle) is carried by

the earth’s rotation in sunlight for most of the day. A person at a southern latitude (right-most yellow circle) is carried by the earth’s rotation in darkness most of the day.


13. Moon revolves about Earth ══► phases.

a. If you didn’t have an explanation, you were not wise.

14. Further tests of wisdom:

a. Eclipses (think of Cortez)(reason why the sun’s path in the sky is the “ecliptic”).

b. Meteors and comets.

c. The motions of the planets.

d. Auroras.

15. Modern astronomy provides very satisfying explanations, . . . , for these and far more arcane phenomena.

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This is the generic diagram showing how the moon and the earth are illuminated with the sun at the left.The direction of the earth’s rotation, the moon’s rotation, and the moon’s orbital motion are also shown.For our first lab, we have a model of this system that is intended to help you, although many students have found it quite confusing.Thus have a close look at this diagram and ponder a bit.It will help.

This diagram illustrates the difference between the length of the month (the time we observe the moon to make a complete circuit about us, from our perspective on the moving earth) and the period of the moon’s orbit about the earth from theperspective of an observer abovethe earth-moon system who is notparticipating in that system’s motion around the sun.People had to sort out these kinds of effects of a moving perspective before they could discover from the motions of the planets the cause of that motion –gravity.We will discuss this more fully later this week, when we discuss Copernicus.

You can really appreciate the large size of the moon’s shadow on the earth as opposed to the very small spot where the solar eclipse is total by looking at the picture of the earth from space that

was taken during the solar eclipse that happened on August 21, 2017.

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A total lunar eclipse is predicted for the end of this month –Jan. 31, 2018.Ask your phone about it and be sure not to miss it.The next total solar eclipse is “scheduled” in the US for 2024.

This maps suggests that the lunar eclipse will not be total asviewed from Minnesota, but it should still be worth seeing.

Aside on Moon Observing Lab

If the moon is full, it is opposite the sun as seen from earth, so it must rsie at 6 PM and set at 6 AM.

(9 hr) x (15 deg/hr) = 135 degrees

It is 9 PM now, so the moon rose 3 hours ago, and hence is now 45 degrees above the horizon.

The Elongation is the number of hours, converted into degrees, by which the moon follows the sun.

Elongation = (sun HA) - (Moon HA)

Now doing any other row in the table is easy. The next row says the moon follows the sun by 9 hours, not 12. It must then rise at 3 PM.

The Moon’s H.A. is 6 hours laterthan in the top row, and it is 3 hours closer to the sun, so the time must now be 3 hours later = 24:00

The time allows you to compute the sun’s hour angle, and vice versa.

Either the elongation or the phase of the moon allows you to compute the rise and set times for the moon, and vice versa.

From any 2 of the sun’s HA, the Moon’s HA, and the elongation, you can compute the other quantity.

So filling out the rest of the table should be pretty easy.

at the end of each chapter in your textbook there are ... 2, implications of the earth’s and...

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