21st Century Astronomy

Laura Kay, Stacy Palen, Brad Smith

Chapter 6

The Tools of the Astronomer - all with Video Answers

Educators

Chapter Questions

Problem 1

Suppose that you are handed a telescope. The tube is roughly as long as your arm, but it is difficult to hold because you can barely get your arms around it. This telescope is most likely a
a. refractor.
b. reflector.

Carlos Henrique De Lima

Carlos Henrique De Lima

Numerade Educator

Problem 1

_____, _____, and _____ build up structures on the terrestrial planets, while _____ tears them down.
a. impacts, erosion, volcanism; tectonism
b. impacts, tectonism, volcanism; erosion
c. tectonism, volcanism, erosion; impacts
d. tectonism, impacts, erosion; volcanism

Zachary Warner

Numerade Educator

Problem 1

You are shopping for telescopes online. You find two in your price range. One of these has an aperture of $20 \mathrm{cm},$ and the other has an aperture of $30 \mathrm{cm} .$ If aperture size is the only difference, which should you choose, and why?
a. The $20 \mathrm{cm}$, because the light-gathering power will be better.
b. The $20 \mathrm{cm}$, because the image size will be larger.
c. The $30 \mathrm{cm}$, because the light-gathering power will be better.
d. The $30 \mathrm{cm}$, because the image size will be larger.

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 1

Suppose that you are handed a telescope. The tube is roughly as long as your arm, but it is difficult to hold because you can barely get your arms around it. This telescope is most likely a
a. refractor.
b. reflector.

Carlos Henrique De Lima

Carlos Henrique De Lima

Numerade Educator

Problem 2

All large astronomical telescopes are reflectors because
a. chromatic aberration is minimized.
b. they are not as heavy as refracting telescopes.
c. they can be shorter than refracting telescopes.
d. all of the above

Donald Albin

Numerade Educator

Problem 2

Geologists can determine the relative age of features on a planet because
a. the ones on top must be older.
b. the ones on top must be younger.
c. the larger ones must be older.
d. the larger ones must be younger.

Kayla Day

Numerade Educator

Problem 3

You are shopping for telescopes online. You find two in your price range. One of these has an aperture of $20 \mathrm{cm}$, and one has an aperture of $30 \mathrm{cm} .$ Which should you choose, and why?
a. The $20 \mathrm{cm}$, because the light-gathering power will be better.
b. The $20 \mathrm{cm}$, because the image size will be larger.
c. The $30 \mathrm{cm}$, because the light-gathering power will be better.
d. The $30 \mathrm{cm},$ because the image size will be larger.

Donald Albin

Numerade Educator

Problem 3

Scientists can learn about the interiors of the terrestrial planets from
a. seismic waves.
b. satellite observations of gravitational fields.
c. physical arguments about cooling.
d. satellite observations of magnetic fields.
e. all of the above

Zachary Warner

Numerade Educator

Problem 4

The Kepler Mission telescope observes primarily in visible light. This telescope is located in space because
a. visible light does not make it through Earth's atmosphere.
b. it is closer to the targets it is observing.
c. it is above atmospheric distortion.
d. it is safe from weather-related disasters.

Donald Albin

Numerade Educator

Problem 4

Earth's interior is heated by
a. angular momentum and gravity.
b. radioactive decay and gravity.
c. radioactive decay and tidal effects.
d. angular momentum and tidal effects.
e. gravity and tidal effects.

Zachary Warner

Numerade Educator

Problem 5

Which of the following can be observed from Earth's surface?
a. radio waves
b. gamma radiation
c. far UV light
d. X-ray light
e. visible light

Donald Albin

Numerade Educator

Problem 5

If a radioactive element has a half-life of 10,000 years, what fraction of it is left in a rock after 40,000 years?
a. $1 / 2$
b. $1 / 4$
c. $1 / 8$
d. $1 / 16$
e. $1 / 32$

Kayla Day

Numerade Educator

Problem 6

Match the following properties of telescopes (lettered) with their corresponding definitions (numbered).
a. aperture
b. resolution
c. focal length
d. chromatic aberration
e. diffraction
f. interferometer
g. adaptive optics
(1) two or more telescopes connected to act as one
(2) distance from lens to focal plane
(3) diameter
(4) ability to distinguish close objects
(5) computer-controlled atmospheric distortion correction
(6) rainbow-making effect
(7) smearing effect due to sharp edge

Donald Albin

Numerade Educator

Problem 6

Lava flows on the Moon and Mercury created large, smooth plains. We don't see similar features on Earth because
a. Earth has less lava.
b. Earth had fewer large impacts in the past.
c. Earth has plate tectonics that recycle the surface.
d. Earth is large compared to the size of these plains, so they are not as noticeable.
e. Earth rotates much faster than either of these other worlds.

Zachary Warner

Numerade Educator

Problem 7

The major advantage CCDs have over other imaging techniques is that they
a. have a higher quantum efficiency.
b. have a linear response to light.
c. yield output in digital format.
d. operate at visible and near-infrared wavelengths.
e. all of the above

Donald Albin

Numerade Educator

Problem 7

Scientists know the history of Earth's magnetic field because
a. the magnetic field hasn't changed since Earth formed.
b. they see today's changes and project backward in time.
c. the magnetic field becomes frozen into rocks, and plate tectonics spreads those rocks apart.
d. they compare the magnetic fields on other planets to Earth's.

Kayla Day

Numerade Educator

Problem 8

Spacecraft are the most effective way to study planets in our Solar System because
a. planets move too fast across the sky for us to image them well from Earth.
b. planets cannot be imaged from Earth.
c. they can collect more information than is available just from images.
d. space missions are easier than long observing campaigns.

Donald Albin

Numerade Educator

Problem 8

Suppose an earthquake occurs on an imaginary planet. Scientists on the other side of the planet detect primary waves but not secondary waves after the quake. This suggests that
a. part of the planet's interior is liquid.
b. all of the planet's interior is solid.
c. the planet has an iron core.
d. the planet's interior consists entirely of rocky materials.
e. the planet's mantle is liquid.

Kayla Day

Numerade Educator

Problem 9

Which of the following Solar System objects has yet to be observed by flyby spacecraft?
a. Uranus
b. Venus
c. Pluto
d. Neptune

Donald Albin

Numerade Educator

Problem 9

Geologists can determine the actual age of features on a planet by
a. radiometric dating of rocks retrieved from the planet.
b. comparing cratering rates on one planet to those on another.
c. assuming that all features on a planetary surface are the
same age.
d. both a and b
e. both b and

Zachary Warner

Numerade Educator

Problem 10

Which of the following are used by astronomers to understand the universe? (Select all that apply.)
a. telescopes
b. particle accelerators
c. neutrino detectors
d. supercomputers
e. gravitational-wave detectors
f. microscopes
g. papers

Donald Albin

Numerade Educator

Problem 10

Impacts on the terrestrial planets and the Moon
a. are more common than they used to be.
b. have occurred at approximately the same rate since the Solar System formed.
c. are less common than they used to be.
d. periodically become more common and then less common.
e. never occur anymore.

Kayla Day

Numerade Educator

Problem 11

T/F: Chromatic aberration is a problem that limits the image quality of reflecting telescopes.

Donald Albin

Numerade Educator

Problem 11

Earth has fewer craters than Venus. Why?
a. Earth's atmosphere protects better than Venus's.
b. Earth is a smaller target than Venus.
c. Earth is closer to the asteroid belt.
d. Earth's surface experiences more erosion.

Kayla Day

Numerade Educator

Problem 12

T/F: In the past, astronomers placed telescopes in highflying aircraft in an effort to rise above the water vapor in Earth's atmosphere.

Donald Albin

Numerade Educator

Problem 12

Scientists propose an early period of heavy bombardment in the Solar System because
a. the Moon is heavily cratered.
b. all the craters on the Moon are old.
c. the smooth part of the Moon is nearly as old as the heavily cratered part.
d. all the craters on the Moon are young.

Zachary Warner

Numerade Educator

Problem 13

$\mathbf{T} / \mathbf{F}:$ Radio telescopes are often used in interferometric arrays to increase light-gathering power.

Donald Albin

Numerade Educator

Problem 13

Scientists know that Earth was once completely molten because
a. the surface is smooth.
b. the interior layers are denser.
c. the chemical composition indicates this.
d. volcanoes exist today.

Zachary Warner

Numerade Educator

Problem 14

T/F: One of the reasons why the Hubble Space Telescope has better spatial resolution than a 4 -meter ground-based telescope is that it has a larger mirror.

Donald Albin

Numerade Educator

Problem 14

What is the main reason that Earth's interior is liquid today?
a. tidal force of the Moon on Earth
b. seismic waves that travel through Earth's interior
c. decay of radioactive elements
d. convective motions in the mantle
e. pressure on the core from Earth's outer layers.

Kayla Day

Numerade Educator

Problem 15

$\mathbf{T} / \mathbf{F}:$ Robotic spacecraft have visited most of the planets and moons of the Solar System.

Donald Albin

Numerade Educator

Problem 15

Mars has a diameter that is approximately half that of Earth. If the interiors of these planets are heated by radioactive decays, how does the heating rate of the interior of Mars compare to that of Earth?
a. The heating rate of Mars is 0.125 times that of Earth.
b. The heating rate of Mars is 8 times that of Earth.
c. The heating rate of Mars is 0.5 times that of Earth.
d. The heating rate of Mars is 4 times that of Earth.
e. The heating rates are about the same.

Kayla Day

Numerade Educator

Problem 16

Refraction is caused by
a. light bouncing off a surface.
b. light changing colors as it enters a new medium.
c. light speeding up as it enters a new medium.
d. light slowing down as it enters a new medium.

Donald Albin

Numerade Educator

Problem 16

In discussing the terrestrial planets, why do we include Earth's Moon?

Zachary Warner

Numerade Educator

Problem 17

The light-gathering power of a 4 -meter telescope is _____ than that of a 2 -meter telescope.
a. 8 times larger
b. 4 times larger
c. 16 times smaller
d. 2 times smaller

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 17

Can all rocks be dated with radiometric methods? Explain.

Zachary Warner

Numerade Educator

Problem 18

Improved resolution is helpful to astronomers because
a. they often want to look in detail at small features of an object.
b. they often want to look at very distant objects.
c. they often want to look at many objects close together.
d. all of the above

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 18

Explain how scientists know that rock layers at the bottom of the Grand Canyon are older than those found on the rim.

Kayla Day

Numerade Educator

Problem 19

The part of the human eye that acts as the detector is the
a. retina.
b. pupil.
c. lens.
d. iris.

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 19

Describe the sources of heating that are responsible for generating Earth's magma.

Zachary Warner

Numerade Educator

Problem 20

Astronomers put telescopes in space to
a. get closer to the stars.
b. avoid atmospheric effects.
c. look primarily at radio wavelengths.
d. improve quantum efficiency.

Donald Albin

Numerade Educator

Problem 20

Explain why the Moon's core is cooler than Earth's.

Zachary Warner

Numerade Educator

Problem 21

The advantage of an interferometer is that
a. the resolution is dramatically increased.
b. the focal length is dramatically increased.
c. the light-gathering power is dramatically increased.
d. diffraction effects are dramatically decreased.
e. chromatic aberration is dramatically decreased.

Donald Albin

Numerade Educator

Problem 21

How do we know that Earth's core includes a liquid zone?

Zachary Warner

Numerade Educator

Problem 22

The angular resolution of a ground-based telescope is usually determined by
a. diffraction.
b. the focal length.
c. refraction.
d. atmospheric seeing.

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 22

How do we know that Earth's core includes a liquid zone?

Zachary Warner

Numerade Educator

Problem 23

A grating is able to spread white light out into a spectrum of colors because of the property of
a. reflection.
b. refraction.
c. dispersion.
d. interference

Donald Albin

Numerade Educator

Problem 23

Study the Process of Science Figure. What evidence makes the impactor theory the currently preferred favorite explanation for the origin of the Moon? What evidence remains to be found to rule out the competing theories?

Kayla Day

Numerade Educator

Problem 24

Which causes the biggest problem in detecting infrared photons from an astronomical object?
a. smog
b. carbon dioxide
c. water vapor
d. light pollution

Donald Albin

Numerade Educator

Problem 24

Compare and contrast tectonism on Venus, Earth, and Mercury.

Zachary Warner

Numerade Educator

Problem 25

Robotic landers are more common than sample-return spacecraft because
a. there is nothing to be learned by bringing back a bunch of rocks.
b. carrying enough fuel to get back to Earth makes sample return expensive.
c. the science instruments on landers are equal to any we have here on Earth.
d. we are nervous about cross-contamination of life-forms.

Donald Albin

Numerade Educator

Problem 25

Explain plate tectonics and identify the only planet on which this process has been observed.

Zachary Warner

Numerade Educator

Problem 26

Galileo's telescope used simple lenses. What is the primary disadvantage of using a simple lens in a refracting telescope?

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 26

Volcanoes have been found on all of the terrestrial planets. Where are the largest volcanoes in the inner Solar System?

Zachary Warner

Numerade Educator

Problem 27

The largest astronomical refractor has an aperture of 1 meter. List several reasons why it would be impractical to build a larger refractor with twice this aperture.

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 27

Explain the criteria you would apply to images (assume adequate resolution) in order to distinguish between a crater formed by an impact and one formed by a volcanic eruption.

Kayla Day

Numerade Educator

Problem 28

Your camera may have a zoom lens, ranging between wide angle (short focal length) and telephoto (long focal length). How does the size of an object in the camera's focal plane differ between wide angle and telephoto?

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 28

What are the primary reasons that the surfaces of Venus, Earth, and Mars have been determined to be younger than those of Mercury and the Moon?

Zachary Warner

Numerade Educator

Problem 29

Optical telescopes reveal much about the nature of astronomical objects. Why do astronomers also need information provided by gamma-ray, X-ray, infrared, and radio telescopes?

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 29

Explain some of the geological evidence suggesting that Mars once had liquid water on its surface.

Zachary Warner

Numerade Educator

Problem 30

For light reflecting from a flat surface, the angles of incidence and reflection are the same. This is also true for light reflecting from the curved surface of a reflecting telescope's primary mirror. Sketch a curved mirror and several of these reflecting rays.

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 30

What evidence supports the theory suggesting that a mass extinction occurred as a consequence of an enormous impact on Earth 65 million years ago?

Zachary Warner

Numerade Educator

Problem 31

Explain constructive and destructive interference.

Donald Albin

Numerade Educator

Problem 31

Study Figure 8.8
a. How has the cratering rate changed over time? Has it fallen off gradually or abruptly?
b. At present, what is the cratering rate compared to that about 4 billion years ago?
c. Explain why this falloff in cratering rate fits nicely in the theory of planet formation.

Kayla Day

Numerade Educator

Problem 32

Consider two optically perfect telescopes having different diameters but the same focal length. Is the image of a star larger or smaller in the focal plane of the larger telescope? Explain your answer.

Rashmi Sinha

Numerade Educator

Problem 32

Study Figure $8.7 .$ Are the vertical and horizontal axes linear or logarithmic? After how many half-lives will the number of parent isotopes equal the number of daughter isotopes? Is this result unique to this example? Why or why not?

Kayla Day

Numerade Educator

Problem 33

Explain why stars twinkle.

Donald Albin

Numerade Educator

Problem 33

Study Figure 8.7 . The destruction of the parent isotope is an example of exponential decay. Is the growth of the daughter isotope an example of exponential growth? How can you tell?

Kayla Day

Numerade Educator

Problem 34

Explain adaptive optics, and how they improve a telescope's image quality.

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 34

Compare Figures 8.18 and $8.23 .$ Which of these regions is older? How do you know?

Kayla Day

Numerade Educator

Problem 35

Explain integration time and quantum efficiency, and how each contributes to the detection of faint astronomical objects.

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 35

Assume that Earth and Mars are perfect spheres with radii of $6,371 \mathrm{km}$ and $3,390 \mathrm{km},$ respectively.
a. Calculate the surface area of Earth.
b. Calculate the surface area of Mars.
c. If 0.72 (72 percent) of Earth's surface is covered with water, compare the amount of Earth's land area to the total surface area of Mars.

Zachary Warner

Numerade Educator

Problem 36

Some people believe that we put astronomical telescopes on high mountaintops or in orbit because doing so gets them closer to the objects they are observing. Explain what is wrong with this popular misconception, and give the actual reason telescopes are located in these places.

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 36

Compare the kinetic energy $\left(=\frac{1}{2} m v^{2}\right)$ of a 1 -gram piece of ice (about half the mass of a dime) entering Earth's atmosphere at a speed of $50 \mathrm{km} / \mathrm{s}$ to that of a 2 -metric-ton SUV (mass $=2 \times$ $10^{3} \mathrm{kg}$ speeding down the highway at $90 \mathrm{km} / \mathrm{h}$.

Kayla Day

Numerade Educator

Problem 37

Humans have sent various kinds of spacecraft-including flybys, orbiters, and landers-to all of the planets in our Solar System. Explain the advantages and disadvantages of each of these types of spacecraft.

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 37

The object that created Arizona's Meteor Crater was estimated to have a radius of 25 meters and a mass of 300 million kg. Calculate the density of the impacting object, and explain what that may tell you about its composition.

Kayla Day

Numerade Educator

Problem 38

If there are meteorites that are pieces of Mars on Earth, why is it so important to go to Mars and bring back samples of the martian surface?

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 38

Using the information in Table 8.1 and Working It Out $8.2,$ determine the relative rates of internal energy loss experienced by Earth and the Moon.

Kayla Day

Numerade Educator

Problem 39

Humans had a first look at the far side of the Moon as recently as $1959 .$ Why had we not seen it earlier-when Galileo first observed the Moon with his telescope in $1610 ?$

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 39

Earth's mean radius is $6,371 \mathrm{km}$, and its mass is $6.0 \times 10^{24} \mathrm{kg}$ The Moon's mean radius is $1,738 \mathrm{km}$, and its mass is $7.2 \times 10^{n} \mathrm{kg}$
a. Calculate Earth's average density. Show your work; do not look this value up.
b. The average density of Earth's crust is $2,600 \mathrm{kg} / \mathrm{m}^{3}$. What does this value tell you about Earth's interior?
c. Compute the Moon's average density. Show your work.
d. Compare the average densities of the Moon, Earth, and Earth's crust. What do these values tell you about the Moon's composition compared to that of Earth and of Earth's crust?

Kayla Day

Numerade Educator

Problem 40

Where are neutrino detectors located? Why are neutrinos so difficult to detect?

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 40

Suppose you find a piece of ancient pottery and find that the glaze contains radium, a radioactive element that decays to radon and has a half-life of 1,620 years. There could not have been any radon in the glaze when the pottery was being fired, but now it contains three atoms of radon for each atom of radium. How old is the pottery?

Kayla Day

Numerade Educator

Problem 41

(a) Study Figure $6.3 .$ For a single-lens system like this, is the image of the sky upright or inverted? If you wished to make the image of the sky right side up, how could you do it? (b) Answer the same questions for the double-mirror system shown in Figure 6.6.

Donald Albin

Numerade Educator

Problem 41

Archaeological samples are often dated by radiocarbon dating. The half-life of carbon-14 is 5,700 years.
a. After how many half-lives will the sample have only $1 / 64$ as much carbon-14 as it originally contained?
b. How much time will have passed?
c. If the daughter product of carbon-14 is present in the sample when it forms (even before any radioactive decay happens) you cannot assume that every daughter you see is the result of carbon-14 decay. If you did make this assumption, would you overestimate or underestimate the age of a sample?

Zachary Warner

Numerade Educator

Problem 42

Study the photograph of light entering and leaving a block of refractive material in Figure $6.7 \mathrm{b}$. Use a protractor to measure the angles of the green light as it enters the block and as it leaves the block. How are these angles related?

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 42

Different radioisotopes have different half-lives. For example, the half-life of carbon-14 is 5,700 years, the half-life of uranium- 235 is 704 million years, the half-life of potassium- 40 is 1.3 billion years, and the half-life of rubidium-87 is 49 billion years.
a. Why wouldn't you use an isotope with a half-life similar to that of carbon-14 to determine the age of the Solar System?
b. The age of the universe is approximately 14 billion years. Does that mean that no rubidium- 87 has decayed yet?

Zachary Warner

Numerade Educator

Problem 43

Many amateur astronomers start out with a 4 -inch (aperture) telescope and then graduate to a 16 -inch telescope. By what factor does the light-gathering power of the telescope increase with this upgrade? How much fainter are the faintest stars that can be seen in the larger telescope?

Prashant Bana

Numerade Educator

Problem 43

Assume that the east coast of South America and the west coast of Africa are separated by an average distance of $4,500 \mathrm{km}$ Assume also that GPS measurements indicate that these continents are now moving apart at a rate of $3.75 \mathrm{cm} / \mathrm{yr}$. If this rate has been constant over geological time, how long ago were these two continents joined together as part of a supercontinent?

Kayla Day

Numerade Educator

Problem 44

The resolution of the human eye is about 1.5 arcmin. What would the aperture of a radio telescope (observing at 21 $\mathrm{cm}$ ) have to be to have this resolution? Even though the atmosphere is transparent at radio wavelengths, humans do not see light in the radio range. Using your calculations and a little logic, explain why.

Donald Albin

Numerade Educator

Problem 44

Shield volcanoes are shaped something like flattened cones. The volume of a cone is equal to the area of its base multiplied by one-third of its height. The largest volcano on Mars, Olympus Mons, is $27 \mathrm{km}$ high and has a base diameter of $550 \mathrm{km}$. Compare its volume with that of Earth's largest volcano, Mauna Loa, which is $9 \mathrm{km}$ high and has a base diameter of $120 \mathrm{km}$

Zachary Warner

Numerade Educator

Problem 45

Assume that you have a telescope with an aperture of 1 meter. Compare the telescope's theoretical resolution when you are observing in the near-infrared region of the spectrum $(\lambda=1,000 \mathrm{nm})$ with that when you are observing in the violet region of the spectrum $(\lambda=400 \mathrm{nm})$.

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 45

Using the data in Table 8.1 , compare the surface gravity on Mars with that on Earth. How does this help explain why the volcanoes on Mars can grow so high?

Kayla Day

Numerade Educator

Problem 46

Assume that the maximum aperture of the human eye, $D$, is approximately $8 \mathrm{mm}$ and the average wavelength of visible light, $\lambda,$ is $5.5 \times 10^{-4} \mathrm{mm}$
a. Calculate the diffraction limit of the human eye in visible light.
b. How does the diffraction limit compare with the actual resolution of $1-2$ arcmin $(60-120 \text { arcsec }) ?$
c. To what do you attribute the difference?

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 46

Go to the U.S. Geological Survey's "Earthquake" website (http://earthquake.usgs.gov/earthquakes/map). Set "Zoom" to "World," set the "Settings" icon in the upper right to "Seven Days, Magnitude $2.5+, "$ and look at the earthquakes for the past week. Were there any really large ones? Compare the map of recent earthquakes with Figure 8.17 in the text. Are any of the quakes in surprising locations? Where was the most recent one? Now change the $^{4}$ Zoom" to the United States (or to "Your location") and change the settings to $^{* 30}$ days, Magnitude $2.5+. "$ Has there been seismic activity, and if so where?

Kayla Day

Numerade Educator

Problem 47

The diameter of the full Moon in the focal plane of an average amateur's telescope (focal length 1.5 meters) is $13.8 \mathrm{mm}$ How big would the Moon be in the focal plane of a very large astronomical telescope (focal length 250 meters)?

Prashant Bana

Numerade Educator

Problem 47

Use Google Earth to explore the Moon, Mercury, and Mars.
a. View all sides of the Moon. Does one hemisphere look more heavily cratered than others, and if so, why?
b. View the planet Mercury. In what ways is Mercury similar to and in what ways different from the Moon? (You might need to get the Mercury KMZ file: http://messenger.jhuapl. edu/the_mission/google.html.)
c. View all sides of the planet Mars. What differences can you see between the northern and southern hemispheres?

Kayla Day

Numerade Educator

Problem 48

One of the earliest astronomical CCDs had 160,000 pixels, each recording 8 bits $(256$ levels of brightness). A new generation of astronomical CCDs may contain a billion pixels, each recording 15 bits $(32,768$ levels of brightness). Compare the number of bits of data that each of these two CCD types produces in a single image.

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 48

Citizen science:
a. Go to the website for "Moon Zoo" (http://moonzoo.org), a project that lets everyone participate in the analysis of images from NASA's Lunar Reconnaissance Orbiter, Read through the FAQ, then click on "Tutorials" and select "How to Take Part." (You will need to create an account if you haven't already done so for another Zooniverse project.) In this project you count craters on the Moon, noting where there are boulders, classifying some of these features, and looking for hardware left over from exploration missions.
b. Go to the website for cosmoquest (http://cosmoquest.org) and click on "Mercury Mappers." You will need to create

Zachary Warner

Numerade Educator

Problem 49

Consider a CCD with a quantum efficiency of 80 percent and a photographic plate with a quantum efficiency of 1 percent. If an exposure time of 1 hour is required to photograph a celestial object with a given telescope, how much observing time would be saved by substituting a CCD for the photographic plate?

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 49

Space missions:
a. Go to the website for NASA's Messenger mission to Mercury (http://messenger.jhuapl.edu). Click on "Gallery" and then "Science Images," and look at a few of the pictures. Are the color images using real or false colors? Click on "News Center." Describe a result.
b. Go to the website for the Mars Science Laboratory Curiosity (http://mars.jpl.nasa.gov/msl), which landed in 2012. What are the latest science results?
c. The Google Lunar X Prize (http://googlelunarxprize.org) goes to the first privately funded team to send a robot to the Moon. The winning robot must travel some distance on the Moon's surface and send back pictures. On the website, click on "Teams" and read about a few that are still competing. What kind of people and companies are on the team? What is their plan to go to the Moon? Aside from this prize, why do they want to go to the Moon: what commercial opportunities on the Moon do they anticipate?

Samantha Baker

Numerade Educator

Problem 50

The VLBA employs an array of radio telescopes ranging across $8,000 \mathrm{km}$ of Earth's surface from the Virgin Islands to Hawaii.
a. Calculate the angular resolution of the array when radio astronomers are observing interstellar water molecules at a microwave wavelength of $1.35 \mathrm{cm}$
b. How does this resolution compare with the angular resolution of two large optical telescopes separated by 100 meters and operating as an interferometer at a visible wavelength of $550 \mathrm{nm}$ ?

Donald Albin

Numerade Educator

Problem 51

When operational, the SVLBI may have a baseline of 100,000 $\mathrm{km} .$ What will be the angular resolution when studying interstellar molecules emitting at a wavelength of $17 \mathrm{mm}$ from a distant galaxy?

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 52

The Mars Reconnaissance Orbiter $(M R O)$ flies at an average altitude of $280 \mathrm{km}$ above the martian surface. If its cameras have an angular resolution of 0.2 arcsec, what is the size of the smallest objects that the $M R O$ can detect on the martian surface?

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 52

The Mars Reconnaissance Orbiter (MRO) flies at an average altitude of $280 \mathrm{km}$ above the martian surface. If its cameras have an angular resolution of 0.2 arcsec, what is the size of the smallest objects that the $M R O$ can detect on the martian surface?

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 53

The martian rover Curiosity can move across the landscape of Mars at speeds of up to $4 \mathrm{cm} / \mathrm{s}$. In contrast, our typical walking speed is about $4 \mathrm{km}$ per hour $(\mathrm{km} / \mathrm{h})$
a. How long would it take Curiosity to cross a soccer field $(110 \text { meters }) ?$
b. How long would it take you to walk the same distance?

Donald Albin

Numerade Educator

Problem 53

The martian rover Curiosity can move across the landscape of Mars at speeds of up to $4 \mathrm{cm} / \mathrm{s}$. In contrast, our typical walking speed is about $4 \mathrm{km}$ per hour $(\mathrm{km} / \mathrm{h})$
a. How long would it take Curiosity to cross a soccer field $(110$ meters )
b. How long would it take you to walk the same distance?

Donald Albin

Numerade Educator

Problem 54

Voyager 1 is now about 125 astronomical units (AU) from Earth, continuing to record its environment as it approaches the limits of our Solar System.
a. How far away is Voyager $1,$ in kilometers?
b. How long does it take observational data to come back to us from Voyager $1 ?$
c. How does Voyager $l$ 's distance from Earth compare with that of the nearest star (other than the Sun)?

Matthew Miranda

Matthew Miranda

Numerade Educator

Problem 54

Voyager 1 is now about 125 astronomical units (AU) from Earth, continuing to record its environment as it approaches the limits of our Solar System.
a. How far away is Voyager $1,$ in kilometers?
b. How long does it take observational data to come back to us from Voyager $1 ?$
c. How does Voyager 1 's distance from Earth compare with that of the nearest star (other than the Sun)?

Donald Albin

Numerade Educator

Problem 55

The speed, wavelength, and frequency of gravitational waves are related as $c=\lambda \times f$. If we were to observe a gravitational wave from a distant cosmic event with a frequency of 10 hertz $(\mathrm{Hz}),$ what would be the wavelength of the gravitational wave?

Donald Albin

Numerade Educator

Problem 55

The speed, wavelength, and frequency of gravitational waves are related as $c=\lambda \times f$. If we were to observe a gravitational wave from a distant cosmic event with a frequency of 10 hertz (Hz), what would be the wavelength of the gravitational wave?

Donald Albin

Numerade Educator

Problem 56

A webcast for the International Year of Astronomy 2009 called "Around the World in 80 Telescopes" can be accessed at http://eso.org/public/events/special-evt/100ha.html. The 80 telescopes are situated all over, including Antarctica and space. Pick two of the telescopes and watch the videos. Do you think these videos are effective for public outreach for the observatory in question or for astronomy in general? For each telescope you choose, answer the following questions:
Does the telescope observe in the Northern Hemisphere or the Southern Hemisphere? What wavelengths does the telescope observe? What are some of the key science projects at the telescope?

Donald Albin

Numerade Educator

Problem 56

A webcast for the International Year of Astronomy 2009 called "Around the World in 80 Telescopes" can be accessed at http://eso.org/public/events/special-evt/100ha.html. The 80 telescopes are situated all over, including Antarctica and space. Pick two of the telescopes and watch the videos, Do you think these videos are effective for public outreach for the observatory in question or for astronomy in general? For each telescope you choose, answer the following questions:
Does the telescope observe in the Northern Hemisphere or the Southern Hemisphere? What wavelengths does the telescope observe? What are some of the key science projects at the telescope?

Donald Albin

Numerade Educator

Problem 57

Most major observatories have their own websites. Use the link in question 56 to find a master list of telescopes, and click on a telescope name to link to an observatory website (or run a search on names from Tables 6.1 and 6.2 ). For the telescope you choose, answer the following questions:
(a) What is this telescope's "claim to fame"-is it the largest? at the highest altitude? at the driest location? with the darkest skies? the newest? (b) Does the observatory website have news releases? What is a recent discovery from this telescope?

Donald Albin

Numerade Educator

Problem 57

Most major observatories have their own websites. Use the link in question 56 to find a master list of telescopes, and click on a telescope name to link to an observatory website (or run a search on names from Tables 6.1 and 6.2 ). For the telescope you choose, answer the following questions:
(a) What is this telescope's "claim to fame"-is it the largest? at the highest altitude? at the driest location? with the darkest skies? the newest? (b) Does the observatory website have news releases? What is a recent discovery from this telescope?

Donald Albin

Numerade Educator

Problem 58

In the chapter we mentioned several radio telescopes under construction. Do a search to find the status of the Allen Telescope Array (ATA), the Square Kilometer Array (SKA), and the Five-hundred-meter Aperture Spherical Telescope (FAST). When is each one scheduled to be completed?

Donald Albin

Numerade Educator

Problem 58

In the chapter we mentioned several radio telescopes under construction. Do a search to find the status of the Allen Telescope Array (ATA), the Square Kilometer Array (SKA), and the Five-hundred-meter Aperture Spherical Telescope (FAST). When is each one scheduled to be completed?

Donald Albin

Numerade Educator

Problem 59

What is the current status of the James Webb Space Telescope, JWST (http://jwst.nasa.gov); that is, when is the expected launch date? How will this telescope be different from the Hubble Space Telescope? What are some of the instruments for the JWST and its planned projects? What is the current estimated cost of the JWST?

Donald Albin

Numerade Educator

Problem 59

What is the current status of the James Webb Space Telescope, JWST (http://jwst.nasa.gov); that is, when is the expected launch date? How will this telescope be different from the Hubble Space Telescope? What are some of the instruments for the JWST and its planned projects? What is the current estimated cost of the JWST?

Donald Albin

Numerade Educator

Problem 60

Pick a mission from Table $6.3,$ go to its website, and see what's new. For the mission you choose, answer the following questions: Is the spacecraft still active? Is it sending images? What new science is coming from this mission?

Donald Albin

Numerade Educator

Problem 60

Pick a mission from Table $6.3,$ go to its website, and see what's new. For the mission you choose, answer the following questions: Is the spacecraft still active? Is it sending images? What new science is coming from this mission?

Donald Albin

Numerade Educator