Astronomy 12 Unit Test Review Charting the Sky

Transcription

1 Astronomy 12 Unit Test Review Charting the Sky Astronomer: Part I- Multiple choice: Answer each question by shading the most appropriate bubble. 01. Astronomy is the study of a. the stars and planets and their movements as well as their affects on the lives and behavior of human beings. b. the weather and of atmospheric processes. c. the structure and evolution of the earth's crust. d. everything in the universe that lies above Earth's atmosphere. 02. Which of the following terms would not be associated with astronomy? a. horoscope b. telescope c. spectroscope d. celestial sphere 03. A planet is an object which a. occurs only in our solar system. b. is too faint to see. c. orbits a star. d. does not generate its own energy from nuclear reactions 04. In astronomical terms, one brief description of a star is a. a small point of light seen only at night. b. a radiant body at least 3 million times as massive as the Earth. c. a bright object with a five-pointed shape. d. a body which shines from its own internal source of energy. 05. A galaxy is a. a large cloud of gas. b. an exploding star. c. the object from which all other objects in the universe were formed. d. a collection of a large number of stars bound by gravity. 06. A(n) is the totality of all space, time, matter, and energy. a. universe b. galaxy c. planet d. star 07. Which of the following is arranged from the smallest to the largest in size? a. planet, star, universe, galaxy b. star, planet, galaxy, universe c. planet, star, galaxy, universe d. universe, galaxy, star, planet 08. What are constellations? a. galaxies of stars b. configurations of bright stars patterned by humans c. areas of the sky, each 15 x 15 degrees d. physical groupings of stars all at the same distance from Earth 09. The picture below shows Orion s Belt. Orion s Belt Orion s Belt is an example of a(n) a. constellation. b. asterism. c. star cluster. d. galaxy. 11. A band of the celestial sphere extending on either side of the ecliptic that represents the path of the different celestial bodies (i.e. Moon, Sun, planets) and contains constellations like Gemini and Aquarius is called the a. North Celestial Pole. b. South Celestial Pole. c. Celestial Equator. d. Zodiac. 12. An imaginary sphere of infinite extent with Earth at its center on which the stars, planets, and other heavenly bodies appear to be located is known as the a. Zodiac. b. celestial sphere. c. atmosphere. d. lithosphere. 14. FILL IN THE BLANKS: Declination is analogous to geographical. Right ascension is analogous to geographical. a. latitude; longitude b. longitude; latitude c. north pole; south pole d. south pole; north pole 15. The time needed for a star on the celestial sphere to make one complete rotation in the sky is referred to as a a. sidereal month. b. solar year. c. sidereal day. d. solar day. 16. The period of time between the instant when the Sun is directly overhead to the next time it is directly overhead is referred to as a a. sidereal month. b. solar year. c. sidereal day. d. solar day. 17. Relative to the stars on the celestial sphere, over the course of a year, the ecliptic is the apparent path of what celestial body? a. Moon b. Sun c. Alpha Centauri d. Earth 18. The Sun rises in the east and sets in the west because a. the Earth rotates on its axis. b. the Earth revolves around the Sun. c. the Moon revolves around the Earth. d. the Earth wobbles on its axis. 19. The point on the ecliptic where the Sun is at its northernmost point above the celestial equator, occurring on or near June 21, is known as Page 1 of 5

2 20. The point on the ecliptic where the Sun is at its southernmost point below the celestial equator, occurring on or near December 21, is known as 21. The date on which the Sun crosses the celestial equator moving southward, occurring on or near September 22 is known as 22. The date during which the Sun crosses the celestial equator, moving northward, occurring on or near March The time required for the constellations to complete once cycle around the sky and return to their starting points, as seen from a given point on Earth, is referred to as a a. synodic month. b. sidereal month. c. tropical year. d. sidereal year. 24. The time interval between one vernal equinox and the next is referred to as a a. synodic month. b. sidereal month. c. tropical year. d. sidereal year. 25. The slow but relatively uniform motion of the earth's rotational axis that causes changes in the coordinate systems used for mapping the sky is known as a. rotation. b. parallax. c. precession. d. revolution. 26. The difference in position of a star as seen from the Earth at different locations around the orbit of the Sun is known as a. revolution. b. transit. c. stellar parallax. d. precession. 27. The appearance of the sunlit face of the Moon at different points along its orbit, as seen from Earth, is referred to as a a. parallax. b. phase. c. lunar eclipse. d. solar eclipse. 28. A eclipse occurs whenever the Moon passes through some portion of the Earth's shadow. a. solar b. lunar c. total d. partial 29. A eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring Earth's view of the Sun. a. solar b. lunar c. total d. partial 30. The darkest part of the shadow is called the a. penumbra. b. umbra. c. baseline. d. dark zone. 31. The part of a shadow where the light source is only partially blocked is called the a. penumbra. b. umbra. c. baseline. d. light zone. 32. TRUE or FALSE. Moonlight is the emission of light from the Moon, produced at its core. T F Answers: 1.d; 2.a; 3.c; 4.d; 5.d; 6.a; 7.c; 8.b; 9.b; 11.d; 12.b; 14.a; 15.c; 16.d; 17.b; 18.a; 19.c; 20.a; 21.d; 22.b; 23.d; 24.c; 25.c; 26.c; 27. b; 28. b; 29. a; 30. b; 31. a; 32. F Part II- Short Answer: Answer each question on the test paper in the space provided. 33. Label the various parts of the celestial sphere below: A B C D E A celestial equator; B ecliptic; C north celestial pole; D south celestial pole; E Earth 34. The solar day is 3.9 minutes longer than the sidereal day. Why is this so? The solar day is longer than the sidereal day because, since it is measured from successive positions of the Sun in the sky or noon times, it accounts for not only the Earth s rotation about its axis but also the small change in its orbit around the Sun. Page 2 of 5

3 35. Why does Earth experience seasons? Be sure to mention Earth s rotational axis and the Sun s energy in your answer. The Earth experiences seasons because it is tilted on its axis. At summer solstice, the Earth is tilted towards the Sun, causing solar rays to fall on the Earth s atmosphere more directly. At this time of year, the Sun remains longer in the sky. These two factors cause the temperature of the atmosphere to increase, leading to summer. At winter solstice, the Earth is tilted away from the Sun, causing solar rays to fall on the Earth s atmosphere less directly. At this time of year, the Sun remains in the sky for shorter periods. These two factors cause the temperature of the atmosphere to decrease, leading to winter. 36. The sidereal year is about 20 minutes longer than the tropical year. a. Why is this so? b. If modern calendars were based on the sidereal year, what would be the effect on timekeeping? The sidereal year is longer than the tropical (solar) year because it is measured as the length of time it takes Earth to revolve around the Sun, based on the position of fixed stars. Precession causes fixed star position to change slightly, leading to approximately 20 additional minutes to the year. If modern calendars used the sidereal year for timekeeping, major events like Easter would fall at different times of the year. 37. Why are some stars seen throughout the year? What do we call these stars? Some stars are seen throughout the year because they are high enough in the sky so that our horizon includes them and they never set. These stars are considered circumpolar. 38. Describe a distance measuring scenario in which the following units would be appropriate: AU, light year and kiloparsec. AU is appropriate for solar system distances; light year and kiloparsec are appropriate for stellar and galactic distances. 39. Describe three ways in which ancient civilizations used constellations. astronomy; timekeeping/calendars; religious observances; oral traditions; navigation 40. Mars is km from Earth. How long would it take a beam of light sent from Earth to reach Mars? time = (distance)/(speed of light) = t = d/c = ( km)/(3.0 x 105 km/s) = 193 seconds 41. The Hubble Space Telescope has a resolution of about 0.05 arc seconds. What is the smallest object it can see on the surface of the Moon? Give your answer in kilometers and meters. Note: the distance from the Earth to the Moon is km. αd D = D = (0.05 )( km)/(206265) = 0.93 km = 93 m (BTW this is why even the best telescopes could never resolve the image of a person standing on the Moon unless they stood 93 m high!) 42. Label the phases of the Moon. Indicate phase name below its image. New Moon Waxing Crescent 1 st Quarter Waxing Gibbous Full Moon Waning Gibbous 3 rd Quarter Waning Crescent 43. Label the lunar eclipse diagram below. Write answers next to the appropriate letters. A: Sun B: Earth C: Moon D: Penumbra E: Umbra 44. Label the solar eclipse diagram below. Write answers next to the appropriate letters. F: Moon G: Sun H: Umbra I: Penumbra J: Earth 45. Explain why we do not see a solar eclipse at every new moon. We do not see a solar eclipse at every new moon because the plane of the Moon s orbit is tilted by about 5 o to the plane of the Earth s orbit (the ecliptic). Page 3 of 5

4 46. Why do we always see the same side of the Moon? We always see the same side of the Moon because the Moon is in synchronous rotation with the Earth. This means that the amount of time it takes the Moon to rotate on its axis is the same as the amount of time it takes the Moon to revolve around the Earth (a.k.a. spin-orbit coupling ). 47. What is the difference between waxing and waning? between crescent and gibbous? Waxing means approaching full moon phase, while waning means approaching new moon phase. Crescent means that less than half of the Moon appears illuminated, while gibbous means more than half of the Moon appears illuminated. 48. Describe different types of solar eclipses. Use the solar eclipse diagram above in your explanation. For a total eclipse to occur, the Moon's angular diameter must be greater than that of the Sun. Areas on the Earth upon which the umbra of the Moon s shadow fall experience a total solar eclipse. Areas on the Earth upon which the penumbra of the Moon s shadow fall experience a partial solar eclipse. Occasionally, the Moon is too far away to completely cover the Sun, and in this case the eclipse is called annular. 49. Describe different types of lunar eclipses. Use the lunar eclipse diagram above in your explanation. A total lunar eclipse occurs when the Moon passes entirely through the umbra of the Earth s shadow. When the Moon passes through the penumbra, a penumbral lunar eclipse occurs. When the Moon is in between the umbra and penumbra, a partial lunar eclipse occurs. 50. One sidereal month is 27.3 days. One synodic month is 29.5 days. Explain this difference. The sidereal month is the time that the Moon takes to go around the Earth once relative to the stars. The synodic month is the time that the Moon takes to go around the Earth relative to the Sun. The synodic month is longer by about 2.3 days. During the sidereal month the Sun appears to move about 27 o due to the Earth s orbital motion. It takes the extra 2.3 days for the Moon to catch up to the Sun. 51. How would the lunar phase cycle change if the Moon orbited in the same direction but with twice the speed? The length of the phase cycle would be half as long as it is now. 52. Describe how Eratosthenes measured the circumference of the Earth. Eratosthenes knew that the Sun never appeared at the zenith at his home in the Egyptian city of Alexandria, which is on the Mediterranean Sea almost due north of Syene. Rather, on the summer solstice in Alexandria, the position of the Sun at local noon was about 7 south of the zenith. This angle is about one-fiftieth of a complete circle, so he concluded that the distance from Alexandria to Syene must be about one-fiftieth of Page 4 of 5

5 Earth s circumference. In Eratosthenes s day, the distance from Alexandria to Syene was said to be 5000 stades. Therefore, Eratosthenes found Earth s circumference to be 50 X 5000 stades = 250,000 stades Unfortunately, no one today is sure of the exact length of the Greek unit called the stade. One guess is that the stade was about one-sixth of a kilometer, which would mean that Eratosthenes obtained a circumference for Earth of about 42,000 kilometers. This is remarkably close to the modern value of 40,000 kilometers. 53. Describe how Aristarchus determined the relative sizes of the Earth, Moon and Sun. From his observations of how long the Moon takes to move through Earth s shadow during a lunar eclipse, Aristarchus estimated the diameter of Earth to be about 3 times larger than the diameter of the Moon. To determine the diameter of the Sun, Aristarchus simply pointed out that the Sun and the Moon have the same angular size in the sky. Therefore, their diameters must be in the same proportion as their distances. In other words, because Aristarchus thought the Sun to be 20 times farther from Earth than the Moon, he concluded that the Sun must be 20 times larger than the Moon. Once Eratosthenes had measured Earth s circumference, astronomers of the Alexandrian school could estimate the diameters of the Sun and Moon as well as their distances from Earth. Page 5 of 5