Review Questions, Chapters 1-3

1. Review Questions, Chapters 1-3 Astro 129: Chapter 1a

2. Review Questions, Chapters 1 Q1.35 A person with good vision can see details that subtend an angle of as small as 1 arcminute. If two dark lines on an eye chart are 2 millimeters apart, how far can such a person be from the chart and still be able to tell that there are two distinct lines? Give your answer in meters. • Where: • D = linear size of the object • = angular size of the object, in arcsec • d = distance to the object

3. Review Questions, Chapters 1 Q1.36 The average distance to the Moon is 384,000 km, and the Moon subtends an angle of ½°. Use this information to calculate the diameter of the Moon in kilometers. • Where: • D = linear size of the object • = angular size of the object, in arcsec • d = distance to the object

4. Review Questions, Chapters 2 Q2.4 Why are different stars overhead at 10:00 p.m. on a given night than two hours later at midnight? Why are different stars overhead at midnight on June 1 than at midnight on December 1? Astro 129: Chapter 1a

5. Review Questions, Chapters 2 Q2.22 What is precession of the equinoxes? What causes it? How long does it take for the vernal equinox to move 1° along the ecliptic? How long does it take for the vernal equinox to move from one constellation to the next. Astro 129: Chapter 1a

6. Review Questions, Chapters 2 Q2.a (a) If you were at the North pole how would the stars appear to move. (b) If you were at the south pole how would the stars appear to move. (c) If you were at the equator how would the stars appear to move looking East. Astro 129: Chapter 1a

7. Review Questions, Chapters 2 Q2.28 On November 1 at 8:30 p.m. you look toward the eastern horizon and see the bright star Bellatrix rising. At approximately what time will Bellatrix rise one week later, on November 8? Astro 129: Chapter 1a

8. Review Questions, Chapters 2 Q2.40 Suppose that you live at a latitude of 40° N. What is the elevation (angle) of the Sun above the southern horizon at noon (a) at the time of the vernal equinox? (b) at the time of the winter solstice? Explain your reasoning. Include a drawing as part of your explanation. Astro 129: Chapter 1a

9. Review Questions, Chapters 3 Q3.5 Astronomers sometimes refer to lunar phases in terms of the age of the Moon. This is the time that has elapsed since new moon phase. Thus, the age of a full moon is half of a 29½-day synodic period, or approximately 15 days. Find the approximate age of (a) a waxing crescent moon (b) a third quarter moon (c) a waning gibbous moon. Astro 129: Chapter 1a

10. Review Questions, Chapters 3 Q3.9 What is the difference between a sidereal month and a synodic month? Which is longer and by how much? Why? Astro 129: Chapter 1a

11. Review Questions, Chapters 3 Q3.18 If there is a total eclipse of the Sun in April, can there be a lunar eclipse three months later in July? Why or why not? Astro 129: Chapter 1a

12. Review Questions, Chapters 3 Q3.a During a lunar eclipse what is the period when the moon is completely within the Earth’s umbra? Take the speed of moon equal to 1km/s, the diameter of the Earth’s shadow on the moon equal to 8700km, and the moon’s diameter of 3500km. Astro 129: Chapter 1a

13. Review Questions, Chapters 3 Q3.31 (a) The Moon moves noticeably on the celestial sphere over the space of a single night. To show this, calculate how long it takes the Moon to move through an angle equal to its own angular diameter (½°) against the background of stars. Give your answer in hours. (b) Through what angle (in degrees) does the Moon move during a 12-hour night? Can you notice an angle of this size? Astro 129: Chapter 1a