Transcript subtends an angle of ½ degree

Phases of the Moon
1
Moon’s Motion
•The moon’s motion is essentially the same as
that of a star (rises in the east, sets in the
west).
•The moon’s motion doesn’t keep pace with the
sun or stars. It completes only 348º of an orbit
in 24 hours.
•Falling 12º behind the sun each day, the moon
completes a full circle (with respect to the sun)
once every 30 days (actually 29). One month!
2
o
90
The Sun-Moon Angle
Determines the phase
of the moon.
180
o
o
0
Animation
o
270
3
Waxing Crescent
First Quarter
Waxing Gibbous to Full
Full to Waning Gibbous
Waning Gibbous to
Third Quarter
Waning Crescent to
New
4
Waning Moon or Waxing Earth
The moon subtends an angle of ½ degree or
the moon has an angular size of ½ degree
6
Craters - Virtually all of the Moon's craters were formed by meteoroid
impacts about 4 billion years ago, in a heavy bombardment period. They
are usually circular in shape and can vary in size. On the Moon the craters
are usually named for famous astronomers, scientists, or explorers. The
majority of craters seen through a telescope are concentrated towards the
highlands and are very old. A few craters are visible in the maria which
makes them younger than the event that formed the
maria.
Highlands - These are the mountain- like structures on the Moon. They
are the oldest part of the Moon's surface and were not formed by tectonic
activity like the mountains on Earth. The highlands were formed by
millions of meteorite craters, one on top of the other, that have pushed the
top layer of the Moon's surface upward.
Maria - These are the dark areas on the Moon that
look like "seas". In Latin the word mare (singular)
means sea. Maria are lowland, flat plains that resulted
from the flow of lava from the Moon's interior when
one or more large impactors struck the Moon and
broke through the crust.
Some Definitions
• The limb is the edge of
a body
• The terminator is the
dividing line between
night and day – it’s
where sunrise and
sunset occur
• These definitions hold
for any body we study
in the solar system
Measuring Mountain Heights
S
M
T
B
C
MB / SM = TB / CB
– Height of a mountain: MB
– CB is the radius of the moon
MB = (TB) (SM) / CB
– TB is the distance from the terminator
to the mountain’s base
– SM is the length of the shadow
Crater Plato
Mons Pico
Crater Cassini
Mons Piton
12