Student Astronomical Society First Meeting!!!!! Wednesday, September 14 7:00 PM 5 th Floor of the Physics Building There will be refreshments!!! Student Astronomical Society First Meeting!!!!! Wednesday, September 14 Wednesday, September 14 Wednesday, September 14 7:00 PM 5 th Floor of the Physics Building There will be refreshments!!! 7:00 PM 5 th Floor of the Physics Building There will be refreshments!!! 7:00 PM 5 th Floor of the Physics Building There will be refreshments!!!
Astronomy 1010 Introduction to Astronomy Lecture 10
The Phases of the Moon From Earth, we see different portions of the Moon’s surface lit by the sun, causing the phases of the moon.
U.S. Naval Observatory Astronomical Applications Department Sun or Moon Rise/Set Table for One Year Sky Gazer Program – Explore, Phases of the Planets, Phases of the Moon Moon Phases http://www.valdosta.edu/~cbarnbau / astro_demos/frameset_moon.html
The Phases of the Moon Evening Sky
The Phases of the Moon Morning Sky
Suppose that on a given evening you notice that the Moon has a crescent shape. This simple observation tells you
that at that particular time the Moon is closer to the Sun than you are.
that at that particular time the Moon is farther from the Sun than you are.
that the line from you to the Moon is exactly at right angles to the line from you to the Sun.
nothing at all about where the Moon is in space compared to you and the Sun.
The dark side of the moon
Is there a dark side of the moon?
Is there a dark side to the moon? Earth exerts tidal forces on the moon’s rocky interior -> It is rotating with the same period around its axis as it is orbiting Earth (tidally locked) -> We always see the same side of the moon facing Earth
The Moon is seen to keep one face toward Earth at all times. If viewed from a point directly above the plane of the planetary system, how does it have to rotate to maintain this alignment? Q?
It must rotate once per year as Earth and Moon orbit the Sun together.
It must rotate once per day.
It must not rotate at all, since we always see the same face from Earth.
It must rotate once per month, or once per orbit around Earth.
Synodic vs Sidereal
Sidereal period = time for moon to complete one full orbit of the earth
Synodic period = time between successive New Moons.
The Moon orbits Earth in a sidereal period of 27.32 days.
27.32 days Earth Moon Fixed direction in space
The Moon’s synodic period (to reach the same position relative to the sun) is 29.53 days (~ 1 month).
Fixed direction in space Earth Moon Earth orbits around Sun => Direction toward Sun changes! 29.53 days
The size of the moon
Lunar motions Inclination of the Moons orbit 5 o Ecliptic plane Moon ’ s Orbital Plane