Bellwork 9/16 What is the difference between the Equatorial system of locating objects and the Azimuth/Altitude system?

Planisphere Practice: What is the RA & Dec. of Arcturus? (near constellation Bootes) RA: ~14hr 15min Dec: ~+20⁰

Planisphere Practice: What is the RA & Dec. of Betelgeuse? (in constellation Orion) RA: ~6hrs Dec: ~+8⁰

Planisphere Practice: Set your planisphere to September 16th at 10:00pm. Name a constellation that is RISING. Taurus Perseus Aries Ect…

Planisphere Practice: Set your planisphere to January 12th at 6:00pm. Name a constellation that is SETTING. Sagitta Cygnus Capricornus Ect…

Planisphere Practice: Set your planisphere to October 15th at midnight. Name a constellation that is close to its ZENITH.  Zenith = bisecting line of the meridian… SO divide your “window” in half horizontally and choose a constellation at that bisecting line Cassiopeia, Perseus

Planisphere Practice: Set your planisphere to March 20th at midnight. Name a constellation that is close to its ZENITH.  Zenith = bisecting line of the meridian… SO divide your “window” in half horizontally and choose a constellation at that bisecting line Ursa major

Bellwork 9/19

Coming Up… Today—Earth-Moon-Sun system Wednesday—Stellar parallax (measuring distances to stars) Monday (9/26)—Cosmic Calendar, some review time Wednesday (9/28)—Unit 1 test

Bellwork 9/13

With a small group… Discuss the articles you read What did you agree or disagree with? What did you find interesting or confusing? In your own mind…is space exploration worth the time and resources we spend? What evidence do you have to back up your claim?

Earth-Moon-Sun System Two primary motions: Rotation: turning or spinning of a body on its axis Revolution: the motion of a body (such as a planet or moon) along a path around some point in space. *Both the moon and the Earth rotate & revolve

Earth-Sun System Earth’s revolution is NOT circular…

Earth-Sun System What causes the seasons? The tilt of Earth’s axis toward and away from the sun as the planet revolves around the sun

Other Earth Motions… Precession Very slow Earth movement “wobbling top” Direction in which Earth's axis points continually changes Movement with the solar system in the direction of the star Vega Revolution with the Sun around the galaxy Movement with the galaxy within the universe

Precession of Earth

Earth-Moon system Moon Phases The relative positions of the Sun, Earth, and Moon constantly change Lunar phases are a consequence of the motion of the Moon and the sunlight that is reflected from its surface It’s because of our perspective from Earth…what we can see at any given time… This is NOT Earth’s shadow!

Lunar motions Moon's period of rotation about its axis and its revolution around Earth are the same Causes the same lunar hemisphere to always face Earth Synodic month Cycle of the moon phases Takes 29 1/2 days

“To obscure light from” Eclipses “To obscure light from” Solar eclipse Moon moves in a line directly between Earth and the Sun Can only occur during the new-Moon phase Lunar eclipse Moon moves within the shadow of Earth Only occurs during the full-Moon phase **For any eclipse to take place, the Moon must be in the plane of the ecliptic at the time of new- or full-Moon **

Solar eclipse

Lunar eclipse

Modeling lab:

Why don’t we have an eclipse every month?? Because the Moon's orbit is inclined about 5 degrees to the plane of the ecliptic, during most of the times of new- and full-Moon the Moon is above or below the plane, and no eclipse can occur The usual number of eclipses is four per year

Why does a Lunar Eclipse Appear Red? If the Earth had no atmosphere, the moon would appear invisible But, the reflected light from the moon travels through our atmosphere

Why does the moon appear red/orange sometimes? Our atmosphere! When the moon is closer to the horizon, the light it reflects must pass through more of the atmosphere More atmosphere = longer wavelength