Astronomy: A Beginner s Guide to the Universe Seventh Edition

Transcription

1 Test Bank to Accompany Astronomy: A Beginner s Guide to the Universe Seventh Edition by Eric Chaisson and Steve McMillan Pearson Education, Inc /11/12

2 Contents Chapter 0 Charting the Heavens: The Foundations of Astronomy... 1 Chapter 1 The Copernican Revolution: The Birth of Modern Science Chapter 2 Light and Matter: The Inner Workings of the Cosmos Chapter 3 Telescopes: The Tools of Astronomy Chapter 4 The Solar System: Interplanetary Matter and the Birth of the Planets Chapter 5 Earth and Its Moon: Our Cosmic Backyard Chapter 6 The Terrestrial Planets: A Study in Contrasts Chapter 7 The Jovian Planets: Giants of the Solar System Chapter 8 Moons, Rings, and Plutoids: Small Worlds Among Giants Chapter 9 The Sun: Our Parent Star Chapter 10 Measuring the Stars: Giants, Dwarfs, and the Main Sequence Chapter 11 The Interstellar Medium: Star Formation in the Milky Way Chapter 12 Stellar Evolution: The Lives and Deaths of Stars Chapter 13 Neutron Stars and Black Holes: Strange States of Matter Chapter 14 The Milky Way Galaxy: A Grand Design Chapter 15 Normal and Active Galaxies: Building Blocks of the Universe Chapter 16 Galaxies and Dark Matter: The Large Scale Structure of the Cosmos Chapter 17 Cosmology: The Big Bang and the Fate of the Universe Chapter 18 Life in the Universe: Are We Alone?

3 Chapter 0 Charting the Heavens: The Foundations of Astronomy 1) Right ascension in the sky is very similar to latitude on the Earth. 2) Latitude and right ascension are coordinate systems used to find objects on the celestial sphere. 3) The celestial sphere is divided into 88 modern constellations. 4) In the sky, declination is measured in degrees north or south of the celestial equator. 5) The south celestial pole is located at a declination of -90 degrees. 6) In general, the brightest star in a given constellation is designated as alpha. 7) Constellations are close clusters of stars, all at about the same distance from the Sun. 8) The closest terrestrial analog to hours of right ascension is angle of longitude. 9) Over 20,000 stars are visible to the naked eye on the darkest, clearest nights. 1

4 Astronomy: A Beginnerʹs Guide to the Universe, 7th ed. 10) A star with a right ascension of 2.6 hrs will rise 2.6 hours after the vernal equinox. Section Ref.: More Prec ) A tropical year is the same as a sidereal year. 12) The sidereal day is determined by the Earthʹs rotation with respect to the stars. 13) The vernal equinox marks the beginning of spring in the northern hemisphere. 14) There are 3,600 arc seconds in a degree. Section Ref.: More Prec ) An hour of right ascension corresponds to 60 degrees in the sky. 16) From Earth, the Sun and Moon have about the same angular diameter. 17) At the solstices, the Sunʹs declination will be 23.5 degrees from the equator. 18) At the equinoxes, the declination of the Sun must be zero degrees. 2

5 Chapter 0 Charting the Heavens 19) As it orbits the Earth, the Moon appears to move its own diameter (0.5 degrees) eastward every hour against the background stars. 20) From full moon to third quarter moon takes about a week. 21) Only people in the Moonʹs umbral shadow can see a total solar eclipse. 22) If we are the Moonʹs penumbra, then we will see a partial lunar eclipse. 23) There is a solar eclipse of some kind every new moon. 24) Eighteen days past new moon, the Moonʹs phase is waning gibbous. 25) A total solar eclipse will only occur when the new moon is both on the ecliptic and at its greatest distance from Earth. 26) The larger the parallax shift, the closer an object is to us. Section Ref.: ) The parallax shift for all stars is very small. Section Ref.: 0.4 3

6 Astronomy: A Beginnerʹs Guide to the Universe, 7th ed. 28) Increasing the baseline will increase the parallax angle. Section Ref.: ) In the scientific method, it is not necessary to test your theory. Section Ref.: ) Drawing on Eratosthenesʹ method, if two observers are due north and south of each other and are separated by 400 km, what is the circumference of their spherical world if they see the same star on their meridian at altitudes of 23 degrees and 47 degrees respectively, and at the exact same time? A) 2,000 km B) 4,000 km C) 6,000 km D) 8,000 km E) 12,000 km Section Ref.: ) The star Wolf 1061 has a parallax of 2.34 arc seconds, while the star Ross 652 has a parallax of 1.70 arc seconds. What can you correctly conclude? A) Both stars are outside the Milky Way galaxy. B) Wolf 1061 must have a larger proper motion than Ross 652. C) Ross 652 must have a larger proper motion than Wolf D) Ross 652 is closer to Earth than Wolf E) Wolf 1061 is closer to Earth than Ross 652. Answer: E Section Ref.: ) The greatest distance above or below the ecliptic the Moon can move is A) 5.2 degrees. B) 23.5 degrees. C) 27.3 degrees. D) 29.5 degrees. E) 30 degrees. Answer: A 4

7 Chapter 0 Charting the Heavens 33) In an annular eclipse, A) the Sun is totally blocked by the Moon. B) the Moon is totally blocked by the Earth. C) the Moon appears as a thin, bright ring. D) the Sun appears as a thin, bright ring. E) the Sun is partially blocked by the Earth. Answer: D 34) If you are in the Earthʹs umbra on the Earthʹs surface, then A) it must be a total solar eclipse. B) it must be a lunar eclipse of some type. C) it is night time. D) the Sun is always visible. E) the Moon is always visible. 35) The synodic month is A) 29.5 days. B) about two days shorter than the sidereal month. C) based on the Moonʹs position relative to the stars. D) the basis of the year we use in our modern calendar. E) caused by both the Earthʹs and Moonʹs rotations. Answer: A 36) If the Moon appears half lit, and is almost overhead about 6:00 AM, its phase is A) waxing crescent. B) first quarter. C) full. D) third quarter. E) waning crescent. Answer: D 37) If new moon fell on March 2nd, what is the Moonʹs phase on March 14th? A) waxing crescent B) first quarter C) waxing gibbous D) full E) waning crescent 5

8 Astronomy: A Beginnerʹs Guide to the Universe, 7th ed. 38) A solar eclipse can only happen during a A) new moon. B) solstice. C) first quarter moon. D) full moon. E) perihelion passage of the Sun. Answer: A 39) What will occur when the full moon is on the ecliptic? A) a total lunar eclipse B) a total solar eclipse C) a partial solar eclipse D) an annular lunar eclipse E) a partial lunar eclipse if the Moon is at perigee Answer: A 40) If you are in the Moonʹs umbral shadow, then you are witnessing A) nighttime. B) a total solar eclipse. C) a total lunar eclipse. D) a partial solar eclipse. E) some kind of lunar eclipse. Answer: B 41) The time for the Moon to orbit Earth, relative to the stars is A) 23 hours, 56 minutes. B) about 7 days. C) 27.3 days. D) 29.5 days. E) 18 years, 11.3 days. 42) The interval from new Moon to first quarter is about a(n) A) hour. B) day. C) week. D) month. E) year. 6

9 Chapter 0 Charting the Heavens 43) The star Thuban in Draco A) lies as the center of the precession cycle. B) was an excellent north pole star in 3,000 BC. C) is brighter than Polaris. D) lies halfway between the bowls of the Big and Little Dippers. E) is used to locate the vernal equinox. Answer: B 44) If Scorpius is now prominent in the summer sky, in 13,000 years it will be best seen A) at the same season; the heavens do not change. B) in the autumn. C) in the winter sky. D) in the spring sky. E) It will not be visible then at all. All of its stars will have vanished by then. 45) If Taurus is now rising at sunset, which constellation will rise at sunset next month? A) Scorpius B) Aquarius C) Gemini D) Aries E) Pisces 46) The fact that the Earth has moved along its orbit in the time it took to rotate once is the reason for A) the difference between solar and sidereal time. B) precession. C) seasons. D) the position of the Celestial Equator. E) Earthʹs 23.5-degree tilt. Answer: A 7

10 Astronomy: A Beginnerʹs Guide to the Universe, 7th ed. 47) When the Moon is directly opposite the Sun in the sky, its phase is A) new. B) waxing or waning crescent. C) first or third quarter. D) waxing or waning gibbous. E) full. Answer: E 48) You note that a particular star is directly overhead. It will be directly overhead again in A) 1 hour. B) 12 hours. C) 23 hours 56 minutes. D) 24 hours. E) 24 hours 4 minutes. 49) As you watch a star, you see it move 15 degrees across the sky. How long have you been watching it? A) 1 hour B) 3 hours C) 15 minutes D) 15 seconds E) 1 minute Answer: A 50) That Polaris will not always be the pole star is due to A) the sidereal day being shorter than the solar day. B) precession shifting the celestial pole. C) the Moon following the ecliptic, instead of the equator. D) the Earthʹs revolution being slightly less than exactly days. E) the Solar winds blowing the Earth farther away from the Sun. Answer: B 8

11 Chapter 0 Charting the Heavens 51) From the horizon to the observerʹs zenith is an angle of A) 30 degrees for observers at a latitude of 30 degrees North. B) 90 degrees for everyone on the Earth. C) 23.5 degrees for observers at the Tropics of Cancer and Capricorn. D) 66.5 degrees for everyone on the Earth. E) 0.0 degrees for an observer at the Earthʹs north pole. Answer: B 52) This diagram explains A) the difference between solar time and sidereal time. B) precession. C) the solar dayʹs relation to the Moon. D) the sidereal dayʹs relation to the seasons. E) the reason for the solstices. Answer: A 9

12 Astronomy: A Beginnerʹs Guide to the Universe, 7th ed. 53) The 26,000 year cycle that changes the poles and equinoxes is called A) a retrograde loop. B) the Earthʹs rotation. C) precession. D) regression. E) revolution. 54) The twelve constellations the solar system bodies move through are the A) equatorial constellations. B) signs of the zodiac. C) nodes of the ecliptic. D) galactic equator. E) stages of heaven. Answer: B 55) A star with a right ascension of 1.0 hours will rise A) 1.0 hours before the vernal equinox. B) 13.0 hours before the vernal equinox. C) 1.0 hours after the vernal equinox. D) 11.0 hours after the vernal equinox. E) at the same time as the vernal equinox. 56) What are constellations? A) Groups of galaxies gravitationally bound and close together in the sky. B) Groups of stars making an apparent pattern in the celestial sphere. C) Groups of stars gravitationally bound and appearing close together in the sky. D) Ancient story boards, useless to modern astronomers. E) Apparent groupings of stars and planets visible on a given evening. Answer: B 57) A star with a declination of degrees will be A) east of the vernal equinox. B) west of the vernal equinox. C) north of the celestial equator. D) south of the celestial equator. E) None of these answers are correct. 10

13 Chapter 0 Charting the Heavens 58) Into how many constellations is the celestial sphere divided? A) 12 B) 44 C) 57 D) 88 E) 110 Answer: D 59) In general, what is true of the alpha star in a constellation? A) It is the brightest star in the constellation. B) It is the easternmost star in the constellation. C) It is the westernmost star in the constellation. D) It is the reddest star in the constellation. E) It is the star that is closest to Earth. Answer: A 60) Like latitude on Earth, in the sky is measured in degrees north and south of the equator. Answer: declination 61) The twelve constellations through which the Sun passes are signs of the. Answer: zodiac 62) The time interval of days is defined as the. Answer: tropical year 63) The time for the Moon to orbit the Earth, relative to the distant stars is the. Answer: sidereal month 64) The apparent annual path the Sun takes through the sky is called the. Answer: ecliptic 11

14 Astronomy: A Beginnerʹs Guide to the Universe, 7th ed. 65) If the Moon rises at sunset, then its phase must be. Answer: full 66) If the Moon is on the ecliptic, new, and at its farthest distance from Earth, we will get a(n) solar eclipse. Answer: annular 67) Our seasons are a consequence of the Earthʹs 23.5 degree. Answer: axial tilt 68) Over the course of the year, the Sunʹs noon altitude varies by degrees. Answer: 47 69) That we do not get eclipses every new and full Moon is due to the degree tilt of the Moonʹs orbit, relative to the ecliptic. Answer: 5.2 (or just 5) 70) The apparent angular shift of any object across a distant background, when viewed from two different places, is called shift. Answer: parallax or parallactic Section Ref.: ) Sirius has a parallax of 0.38ʺ, while Alpha Centauriʹs is 0.77.ʺ Alpha Centauri is about as Sirius. Answer: twice as close, or half as far Section Ref.: ) If one star has a parallax ten times larger than anotherʹs, the first star is. Answer: ten times closer than the second Section Ref.: ) If two observatories on opposite sides of the Earth were to measure the position of a star to calculate its parallax, then the diameter of the Earth would be the. Answer: baseline Section Ref.:

15 Chapter 0 Charting the Heavens 74) One of the requirements of the Scientific Method is that an experiment must be. Answer: repeatable Section Ref.: ) What do both latitude on Earth and declination in the sky measure? Answer: Angular distance in degrees above or below the geographical and celestial equators. 76) How is right ascension similar to longitude on Earth? Answer: Both measure positions east or west from a fixed point; Greenwich on Earth, the vernal equinox in the sky. 77) What are the minimum and maximum values for declination in the sky for both north and south? Answer: From the equator at 0 degrees, to +90 degrees for the north celestial pole, and down to -90 degrees for the south celestial pole. 78) How are right ascension in the sky and longitude on Earth different? Answer: Right ascension is measured in units of time eastward from the vernal equinox, while longitude is measured in degrees east or west of the Greenwich meridian. 79) Define the celestial sphere. Answer: An imaginary hollow sphere, with Earth at its center, on which all the stars (and other celestial bodies) are fixed. As the sphere rotates around the Earth, the stars move across our sky. 80) What are the minimum and maximum values for right ascension in the sky? Answer: From 0 to 24 hours, going eastward from the vernal equinox. 81) Which is longer, the sidereal or solar day? By how much? Answer: The solar day is approximately four minutes longer than the sidereal day. 13

16 Astronomy: A Beginnerʹs Guide to the Universe, 7th ed. 82) At the solstice, what is the maximum angle the Sun can be above or below the equator? Answer: degrees in summer and degrees in winter. 83) How far above or below the ecliptic can the Sun move? Answer: The Sun follows the ecliptic eastward across the sky, never leaving it. 84) If intending to teach his students the constellations by season, why would an astronomy instructor be advised to always assign the stars in the current western sky at the beginning of each term? Answer: As the Earth revolves around the Sun, the Sun appears to move one degree eastward per day. These stars are, therefore, soon lost in the Sunʹs glare. 85) Which star shows the least motion in the northern sky over the course of an hour? Answer: Polaris, the North Star, lies within a degree of the celestial pole, and does not move noticeably with the naked eye over an entire night. 86) Pensacola, Florida lies at a latitude of 30 degrees north. Where is Polaris in its sky? Answer: 30 degrees high in the north 87) How far above or below the equator can the Sun appear to move? Why? Answer: The Earthʹs axial tilt means the Sunʹs declination can reach 23.5 degrees north or south of the equator at the solstices. 88) What happens on or about March 20th, and what does the name signify? Answer: The vernal equinox, because the days and nights are approximately equal in length. 89) Why are some solar eclipses total, and others annular? Answer: The Moonʹs orbit is not a perfect circle. When the Moon is closer to Earth, it is big enough to cover the Sun completely; when it is too far away it appears smaller, so a ring of sunlight is still seen. 14

17 Chapter 0 Charting the Heavens 90) What is the length of the sidereal month, and how is it determined? Answer: It takes 27.3 days for the Moon to revolve around us and return to the same position against the background of stars. 91) How long does the synodic month take, and how it this observed? Answer: The phase cycle of the Moon takes 29.5 days to return to exactly the same phase. 92) How far above and below the celestial equator can the Sun move? Answer: The Sun never appears more than 23.5 degrees above or the below the celestial equator. 93) The first quarter moon rises about noon today; what will its phase be, and when will it rise tomorrow? Answer: It will be waxing gibbous, and rise about 1 PM by the next day. 94) The last quarter moon rises tonight about midnight; when will it rise, and what will its phase be tomorrow night? Answer: It will rise about an hour later, about 1 AM, and be a waning crescent by then. 95) If the Moon rises exactly at sunset, what will its phase be? Why? Answer: The phase will be full because it is rising opposite the Sun. 96) Why is Polaris not always the pole star, and when does it get another chance? Answer: Precession of the Earthʹs axis of rotation takes around 26,000 years. 97) If Sirius transits my local meridian tonight at 6:43 PM, when will it transit tomorrow? Answer: At 6:39 PM tomorrow night, as the Earth spins once in a sidereal day. 15

18 Astronomy: A Beginnerʹs Guide to the Universe, 7th ed. 98) Compare and contrast latitude and declination. How does each relate to your position on Earth? Answer: Both are measured in degrees north or south of the equator, and are used to find positions on the Earth or in the sky. If you are at latitude 30 degrees north, then the stars that pass through your zenith (directly overhead) will have a corresponding declination of +30 degrees. 99) Compare and contrast longitude and right ascension. Answer: Longitude is measured in degrees both east and west of the Greenwich meridian, but right ascension is measured in units of time as the Earth rotates, and goes only eastward from the vernal equinox. 100) Compare hours of right ascension to time zones on the Earth. Answer: Like time zones, hours of right ascension are 15 degrees wide, and they run eastward across the sky from the Vernal Equinox, much like the time zones originate from the Prime Meridian. 101) The Sun and stars rise in the east, and set in the west. Contrast ancient and modern explanations for this observation. Answer: The ancients thought there was a vast celestial sphere, spinning over our heads once a day, and that the stars, Sun, Moon, and planets are all carried along for the ride. We now recognize it is the Earth itself that rotates eastward, creating this apparent westward motion of celestial bodies. 102) Contrast the sidereal and solar days. Answer: The Earth rotates once on its axis every 23 hours, 56 minutes, and thus turns to face the same distant star in that interval. But we are also revolving around the Sun at one degree eastward per day, hence the Sun appears to have moved eastward from one day to the next, and it takes a full 24 hours to align with the Sun again. 103) Why can many more people witness a total lunar eclipse than a total solar eclipse? Answer: For a total solar eclipse to be seen, the observer must be in the Moonʹs umbra, a shadow only about a hundred miles across, while everyone on the night side of the Earth can look up to witness the full moon moving though our shadow. 16

19 Chapter 0 Charting the Heavens 104) What conditions are necessary for a total solar eclipse? Answer: The Moon must be at new phase (directly between Earth and the Sun), it must also be both at the closer distance in its orbit and on the ecliptic (crossing a node). Only people on those parts of the Earth where the Moonʹs umbral shadow passes will see a total solar eclipse. 105) What is the astronomical significance of 26,000 years? Answer: The Earthʹs rotational axis itself rotates over this precession cycle, which also changes the location of the poles, equinoxes, and solstices in the sky. 106) Describe how Eratosthenes measured the circumference of our planet. Answer: Using the fact that the noon solstice Sun was directly overhead at Syene, on the Tropic of Cancer, yet was 7 degrees south of the zenith in Alexandria, Eratosthenes realized this was due to the curvature of the Earth, and that the 7 degrees was about 1/50th of the Earthʹs total circumference, so the Earth must be about fifty times larger in circumference than the 800 kilometer separation between Alexandria and Syene, or about 40,000 kilometers around. 107) Which is longer, the sidereal or synodic month? Why? Answer: The synodic month takes an extra two days, because the Earth is also revolving around the Sun, so after 27.3 days the Moon returns to the same place among the stars, but the Earth has revolved about 27 degrees ahead of where it was last month; it takes the Moon two days to catch up to us. 108) We get a new and full moon every month. Why donʹt we get two eclipses every month? Answer: The Moonʹs orbit is tilted 5.2 degrees to the Earthʹs orbit (the ecliptic), and the disks of the Sun and Moon are only about.5 degrees wide. Most months the new and full moon pass too far from the ecliptic for the Earthʹs and Moonʹs shadows to make eclipses occur. 17

20 Chapter 1 The Copernican Revolution: The Birth of Modern Science 1) According to Newtonʹs third law, when the Voyager probes passed Jupiter in 1979, they exerted exactly the same force on Jupiter as the giant planet did on them. Section Ref.: 1.4 2) Compared to when it was on the surface, a satellite in an orbit whose radius is about 4 times the Earthʹs radius will experience about 1/16 the force due to the Earthʹs gravity. Section Ref.: 1.4 3) According to Newtonʹs second law, if you double the force acting on a body, the acceleration will double. Section Ref.: 1.4 4) According to Newtonʹs first law, an object traveling in a circle does not have a force acting on it. Section Ref.: 1.4 5) Keplerʹs third law allows us to find the average distance to a planet from observing its period of rotation on its axis. Section Ref.: 1.3 6) According to Keplerʹs third law, if you know the planetʹs orbital period, you can find its average distance from the Sun. Section Ref.: 1.3 7) A planet (or comet) will speed up as it approaches the Sun. Section Ref.:

21 Chapter 1 The Copernican Revolution: The Birth of Modern Science 8) Kepler found the orbits of planets are ellipses, not circles. Section Ref.: 1.3 9) Kepler relied heavily on the telescopic observations of Galileo in developing his laws of planetary motion. Section Ref.: ) Keplerʹs third law relates the square of the planetʹs orbital period in years to the cube of its average distance from the Sun in astronomical units. Section Ref.: ) Among Galileoʹs discoveries with his telescope were sunspots. Section Ref.: ) Galileoʹs observations of the entire phase cycle of Venus proved that Ptolemyʹs epicycles could not be correct in keeping Venus between us and the Sun. Section Ref.: ) According to Copernicus, retrograde motion occurs at opposition for the outer planets. 14) In Ptolemyʹs geocentric model, the planetʹs motion along its deferent is all that is needed to understand retrograde motion. 15) Copernicus believed the Earth was the center of all celestial motion. 19

22 Astronomy: A Beginnerʹs Guide to the Universe, 7th ed. 16) In Ptolemyʹs geocentric model, retrograde motion occurs when the planet is closest to us, on the inside portion of the A) deferent. B) ellipse. C) epicycle. D) equant. E) ecliptic. 17) In Ptolemyʹs geocentric model, the normal eastward motion of the planets was along A) a deferent. B) an epicycle. C) a retrograde loop. D) an ellipse. E) the equant. Answer: A 18) Copernicusʹ Heliocentric theory explains that A) planetary orbits are elliptical in shape. B) the Sun lies at one focus of an ellipse. C) Venus retrogrades when she overtakes us at inferior conjunction. D) all planets lie between the Sun and Earth. E) Mars will retrograde when it reaches a certain position on its epicycle. 19) According to Copernicus, retrograde motion for Venus must occur around A) inferior conjunction, when it passes between us and the Sun. B) quadrature, when the planet is 90 degrees away from the Sun. C) greatest elongation, when the planet is farthest from the Sun. D) superior conjunction, when the planet is on the far side of the Sun. E) opposition, when the planet lies opposite the Sun in the sky. Answer: A 20

23 Chapter 1 The Copernican Revolution: The Birth of Modern Science 20) According to Copernicus, the retrograde motion for Mars must occur A) at inferior conjunction, when Mars laps the Earth and passes between us and the Sun. B) at superior conjunction, when Mars lies on the far side of the Sun. C) at quadrature, when Mars lies exactly 90 degrees east or west of the Sun. D) at greatest elongation, when Mars can get up to 47 degrees from the Sun. E) at opposition, when the Earth overtakes Mars and passes between Mars and the Sun. Answer: E 21) A fatal flaw with Ptolemyʹs model is its inability to predict the observed phases of A) the Sun during an eclipse. B) the Moon in its monthly cycle. C) Mercury and Venus. D) Mars and Jupiter. E) Jupiter and Saturn. Section Ref.: ) Which of these was NOT seen telescopically by Galileo? A) sunspots B) Venusʹ phase cycle C) Four moons around Jupiter D) stellar parallax E) craters and mare on the Moon Answer: D Section Ref.: ) Which of these observations of Galileo refuted Ptolemyʹs epicycles? A) the complete cycle of Venusʹ phases B) the rotation of sunspots across the Sunʹs surface C) the revolution of Jupiterʹs moons around it D) the craters on the Moon E) the visibility of many more stars with the telescope Answer: A Section Ref.: ) Galileo found the rotation period of the Sun was approximately A) a day. B) a week. C) a month. D) three months. E) a year. Section Ref.:

24 Astronomy: A Beginnerʹs Guide to the Universe, 7th ed. 25) Tycho Braheʹs contribution to Keplerʹs Laws of Planetary Motion were A) his detailed and accurate observations of the planetsʹ positions. B) his observations of Jupiterʹs moons. C) a mathematical explanation of epicycles. D) a precise lunar calendar. E) the correct explanation of lunar phases. Answer: A Section Ref.: ) Keplerʹs first law worked, where Copernicusʹ original heliocentric model failed, because Kepler described the orbits as A) elliptical, not circular. B) much larger than Copernicus had envisioned. C) around the Sun, not the Earth. D) being on equants instead of epicycles. E) complex, with epicycles to account for retrograde motions. Answer: A Section Ref.: ) When a planetʹs orbit takes it closest to the Sun, itʹs called A) vernal equinox. B) aphelion. C) perihelion. D) crossing the ecliptic. E) none of these; a planetʹs distance from the Sun never changes. Section Ref.: ) A planet whose distance from the Sun is 3 AU would have an orbital period of how many Earth-years? A) 3 B) 27 C) 3 D) 9 E) 81 Answer: B Section Ref.:

25 Chapter 1 The Copernican Revolution: The Birth of Modern Science 29) The force of gravity varies with the A) product of the two masses. B) inverse of the distance separating the two bodies. C) inverse square of the distance separating the two bodies. D) Both A and B are correct. E) Both A and C are correct. Answer: E Section Ref.: ) A circular orbit would have an eccentricity of A) 0. B) between 0 and 0.5. C) between 0.5 and 1. D) exactly 1.0. E) infinity. Answer: A Section Ref.: ) How much stronger is the gravitational pull of the Sun on Earth, at 1 AU, than it is on Saturn at 10 AU? A) 5 B) 10 C) 25 D) 100 E) 250 Answer: D Section Ref.: ) If the distance between two asteroids is doubled, the gravitational force they exert on each other will A) also be doubled. B) be half as great. C) be one fourth as great. D) will be 1/16 as great. E) be four times greater. Section Ref.: ) Because he failed to observe stellar, Aristotle wrongly concluded we could not be in orbit around the Sun. Answer: parallax 23

26 Astronomy: A Beginnerʹs Guide to the Universe, 7th ed. 34) The mean distance between the Earth and Sun is called the. Answer: astronomical unit 35) Ptolemyʹs model was, with the Earth fixed in the center of the universe. Answer: geocentric 36) The model of used circular deferents and epicycles in a geocentric universe to explain planetary motions. Answer: Ptolemy 37) The time for a planet to revolve around the Sun is its. Answer: orbital period or year 38) When Earth overtakes Mars, the outer planet retrogrades near. Answer: opposition 39) The ʺguest starʺ observed by the Chinese in 1054 is now known to have been a. Answer: supernova 40) Galileoʹs discovery of four moons orbiting provided new support for the ideas of Copernicus. Answer: Jupiter Section Ref.: ) For Galileo, the observation of the phases of proved that Ptolemyʹs geocentric model with epicycles was wrong. Answer: Venus Section Ref.: ) The hypothesis is that the Earth does not occupy any special place in the universe. opernican Section Ref.:

27 Chapter 1 The Copernican Revolution: The Birth of Modern Science 43) The three laws of planetary motion by allowed us to predict planetary motion. Answer: Kepler Section Ref.: ) While both Ptolemy and Copernicus assumed all orbits were, Keplerʹs first law corrected this and made planetary motion predictable. Answer: circles Section Ref.: ) Keplerʹs theories were based on the very accurate observations made by. Answer: Tycho Brahe Section Ref.: ) According to Newtonʹs laws, the planets orbit the Sun due to. Answer: gravity Section Ref.: ) According to Newton, the gravity of the is needed to explain planetary orbits. Answer: Sun Section Ref.: ) In Newtonʹs first law, the of a body causes it to resist changes in its motion Answer: inertia Section Ref.: ) According to Newtonʹs second law, when the same force acts on two bodies, the body with the larger mass will have the acceleration. Answer: smaller Section Ref.: ) Newton found that gravity varied with the of the distance between the two bodies pulling on each other. Answer: inverse square Section Ref.: ) How did Ptolemy explain the retrograde motion of Venus? Answer: The epicycle for both Mercury and Venus is always centered on the Earth -Sun line, so they always orbit between us and the Sun. 25

28 Astronomy: A Beginnerʹs Guide to the Universe, 7th ed. 52) How did Ptolemy explain the retrograde motion of Mars? Answer: Mars will retrograde on the inner portion of its epicycle, when it is closest to us and its motion on the epicycle is more obvious than its motion along its deferent. 53) What ʺimperfectionsʺ on the Moon were visible to Galileoʹs telescopes? Answer: Impact craters, mountains, and dark lava flows, or mare. Section Ref.: ) What is meant by the astronomical unit? Answer: The astronomical unit, or AU, is the mean distance between the Earth and Sun. Section Ref.: ) How did Tychoʹs detailed observations of Marsʹ brightness help show that its orbit could not be circular? Answer: Tycho noted that at some oppositions, Mars was much brighter than at others, suggesting that Mars must be closer to us when it was brighter. 56) What did Galileo discover through his telescope when he looked at Jupiter, and how did it refute the Ptolemaic model? Answer: That Jupiter had four moons in orbit about it, so Earth was not the center of all things. Ptolemy contended that all things move around the Earth. Section Ref.: ) The speed of light (and radio waves) is 300,000 km/s. How far away is a spacecraft if its radio signal takes 10 minutes to reach Earth? Answer: 180,000,000 km Section Ref.: ) What did Galileo discover when looking at the Sun with his telescope, and how did this support Copernicus? Answer: Sunspots, which rotated across the Sunʹs face, showing that the Sun was not perfect and it (and Earth) could rotate on its axis. Section Ref.: ) Explain how the eccentricity describes the shape of an ellipse. Answer: The higher the eccentricity, the more elongated the oval; a circle has an eccentricity of zero, while very stretched-out comet orbits approach an eccentricity of one. Section Ref.: