- 1. Consult the any star chart showing the southern sky. What constellation
includes the south celestial pole? Is there a conspicuous southern "pole
star" corresponding to Polaris in the northern hemisphere
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- 2. Why do the three units of right ascension have names that suggest
units of time? How would you convert these units into standard units of
angular measure? (You may wish to consult the celestial sphere definitions
listed in the book or those available via the Web
Destinations for Chapter 1 .)
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- 3. Often, when you see a thin crescent moon in the evening sky, the
rest of the moon's disk doesn't seem to be completely dark. Can you think
of an explanation for this fact?
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- 4. Consult the following table of umbral lunar eclipses. (An umbral
lunar eclipse occurs when the Moon enters the full shadow, or umbra, of
the Earth, as opposed to its partial shadow, or penumbra.) Umbral Lunar
Eclipses 1996-2000 Year Date Time of Mideclipse Length of Totality Length
of Eclipse (UT) (Hours:Min) (Hours:Min) 1996 April 4 0:11 1:26 3:36 1996
September 26 2:55 1:10 3:22 1997 March 24 4:41 Partial (92%) 3:22 1997
September 16 18:47 1:02 3:16 1999 July 28 11:34 Partial (40%) 2:22 2000
January 21 4:45 1:16 3:22 2000 July 16 13:57 1:46 3:56 Times are given
in Universal Time. Note that total lunar eclipses will occur for example
in March and September, 1997. Why are there only typically one to two such
eclipses during the course of the year rather than 12?
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- 5. Consult the following table of solar eclipses for a similar period
as given in the previous question. Total and Annular Solar Eclipses 1995
- 2000 1995 Apr 29 Annular Solar Eclipse 1995 Oct 24 Total Solar Eclipse
1997 Mar 09 Total Solar Eclipse 1998 Feb 26 Total Solar Eclipse 1998 Aug
22 Annular Solar Eclipse 1999 Feb 16 Annular Solar Eclipse 1999 Aug 11
Total Solar Eclipse Note that no solar eclipses will take place in 1996.
Are total and annular solar eclipses much rarer in general, for all of
the Earth, than umbral lunar ones? Why are there some years that do not
have a particular type of eclipse ? What would happen if we included penumbral
(partial shadow) lunar and partial solar eclipses? (For more information,
see the eclipse resources listed in the Web
Destinations for Chapter 1 .)
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- 6. Referring to the tables given the previous two questions, why was
it possible for us to give the exact starting and ending times for the
lunar eclipses valid for all observers on the night side of the Earth,
but not possible to do so for all observers on the day side of the Earth
for the table of solar eclipses? Which type of eclipse would be rarer to
see for an observer at a particular fixed location on the Earth's surface?
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- 7. Even the diameter of the Earth does not provide a long enough baseline
to measure the parallax of objects as distant as the stars. Can you think
of a way of obtaining a longer baseline for measuring parallax? (Hint:
see Figure 1.12 in the text.)
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