Chapter 2. The Sky
a. What are the constellations? Asterisms? How are stars named in each constellation? What is meant
by Alpha Orionis? Beta Orionis? Delta Cephei?
b. How do we measure the brightness of stars? Who invented the magnitude system? How much
brighter is a 5th magnitude star than a 10th magnitude star? What is the apparent visual magnitude of
the Sun?
c. Remember that a difference of 1 magnitude is a brightness difference of 2.5.
d. Look at the Figures and read the figure captions. Where is Polaris? What is latitude and longitude?
What is the latitude and longitude of Tempe? What is the Celestial Sphere, Angular measurement, the
horizon? Where is the zenith?
e. What is a circumpolar star? How does the sky appear to change as we move north and south? What
is the North Celestial Pole? South Celestial Pole? Celestial Equator?
f. Know degrees, minutes of arc, and seconds of arc. Know why the angular diameter is different from
the linear diameter.
g. What causes Precession. Which star is now the Pole Star? What star will be the Pole star in 12,000
years?
h. What is meant by the Ecliptic? Which stars are overhead at midnight through the year? Why do they
change during the year?
I. What is the inclination of the Earth's Poles to the ecliptic? What is meant by the Vernal and
Autumnal Equinoxes? The Summer and Winter Solstices?
j. What causes the Seasons? How does the rising and setting points of the Sun change through the
year? Where, approximately, does the Sun rise at the Summer and Winter Solstices?
k. What is meant by perihelion? Aphelion? Perigee? Apogee? (Used here but defined until the next
chapter.)
l. Remember that the planets move along the ecliptic.
m. Read about the Milankovitch hypothesis. It may be correct.