Lecture 4 Flashcards
(17 cards)
at the south pole, you can only see stars in which celestial hemisphere?
at the equator, what can you see?
a) southern hemisphere
b) can see everything
what is the diurnal circle?
the apparent pat on the sky a celestial object takes over 24 hrs
the altitude of polaris is equal to what?
your latitude
what are circumpolar stars?
- stars close to the north celestial pole
- don’t rise or set
- remains above the horizon and makes circles around the NCP
what stars never rise above the horizon?
stars close to the south celestial pole
why does it look like stars rise in the east and set in the west?
b/c stars have circles that are partly above the horizon and partly below it
visibility of a constellation depends on what?
location relative to the sun
must be away from su to be seen at night
what is the earth’s obliquity?
earth’s axis tilt w/ respect to plane of its orbit
23.5
what is the ecliptic plane?
plane of the earth’s orbit around the sun
what is the angle b/w the ecliptic and celestial equator?
23.5
why are there longer days in the northern hemisphere in the summer?
b/c of a longer distance
what are the set of stars that lie on the ecliptic plane?
constellations of the zodiac
what is the solstice?
when the separation b/w celestial equator and ecliptic ix maximal
occurs twice per year (june 21 and dec 21; longest and shortest)
what is the equinox?
when the planes (celestial equator and ecliptic) intersect
what does the moon’s appearance depend on?
location relative to the sun
can be seen by the phases of the moon
how many days does it take the moon to go through one cycle?
29.5
describe lunar eclipses.
when the earth comes b/w sun and moon
earth casts a shadow on the moon
only happens at full moon
moon appears red b/c red light is refracted by earths atmosphere
