General Astronomy, 29:61
Fall, 2005
Fourth Homework Set...September 16, 2005.
Due September 23, 2005

Office hours are for discussing homework (among other things). Office hours for the week of September 19 will be:
Monday: 11:30-12:30.
Thursday: 10:30-11:30 and 1:00 - 2:00.
Regular office hours will return the following week. Note: Data for some of these problems can be found in the appendix of the textbook.

(1) Calculate the maximum and minimum angular size of the Moon as seen from Earth. Use data from notes and in the textbook.

(2) Compare the results from #1 with the angular size of the Sun (again, check the notes and textbook for data). Is the angular size of the Moon larger, smaller, or sometimes one, and sometimes the other?

(3) The duration of solar eclipses varies, with a minimum of a few tens of seconds to a maximum of about eight minutes. State some of the conditions that must be fulfilled for a long eclipse.

(4) Below I have listed the dates and times of the vernal equinox for several years in the last decade. Why does the time of the vernal equinox change from one year to the next? What is the time difference from one year to the next, and why does it have this value? Remember: the term vernal equinox is used both for a point on the sky and the time of an astronomical event.
$\bullet$ 1996 ...Sept.22, 18h Universal Time (Universal Time is mean solar time in Greenwich, England).
$\bullet$ 1997 ...Sept.23, 0h Universal Time
$\bullet$ 1998 ...Sept.23, 6h Universal Time
$\bullet$ 1999 ...Sept.23, 11h Universal Time
$\bullet$ 2000 ...Sept.22, 17h Universal Time

(5) The sidereal period of Jupiter's moon Callisto is 16.69 days. If you were on Jupiter (floating in its atmosphere in a balloon) what would you see as the synodic period of Callisto? You will need data from the textbook to answer this.

(6) Here's one with the SC1 chart. Get out a ruler, too! You observe the first quarter moon. Because it is nestled in among some bright stars, you can measure its Right Ascension and Declination, which are RA=16h30m, DEC=-13.4 degrees. Will there be an eclipse of the Moon in another week? Obviously, you have to give your reasons. Hint #1: First find the location of the Moon on your star chart. Hint #2: Think about the requirements for an eclipse.