Grab your text book Chapter 1 Astronomy Today 7th Edition Chaisson/McMillan Grab your text book

Charting the Heavens Day 4 High overhead on a clear, dark night, we can see a rich band of stars known as the Milky Way—so-called for its resemblance to a milky band of countless stars. All these stars (and more) are part of a much larger system called the Milky Way Galaxy, of which our star, the Sun, is one member. This single exposure, dubbed “the Going to the Stars Road,” was made at night with only the Moon’s light illuminating the terrain on the continental divide at Logan Pass in Glacier National Park, near the Montana/Alberta border. (© Tyler Nordgren)

Local co-ordinate systems Based on the objects above the plane of the horizon Altitude is the angle above the horizon star altitude horizon NORTH STAR HAS AN ALTITUDE OF 0° IF YOU ARE ON THE EQUATOR THE ALTITUDE OF THE NORTH STAR=YOUR LATITUDE ON EARTH!!!

A ROUGH WAY TO ESTIMATE ALTITUDE PINKY =1° 3 FINGERS=3° FIST = 10°

Local Co-ordinate System Azimuth – starts with north a 0° and south is 180° Zenith is 90° zenith

North Star Even though Polaris is currently the North star, it doesn’t lie due North –and eventually will move Vega will be our North Star, Why do you think this is happening? Discuss with your elbow partner, write down your thoughts on your white board, be ready to defend them.

CIRCUMPOLAR STARS STARS THAT NEVER GO BELOW THE HORIZON CAN ALWAYS BE SEEN AT NIGHT http://upload.wikimedia.org/wikipedia/commons/2/21/Zirkumpolar_ani.gif

The North Star Polaris, our current North Star is the 49th brightest star in the night sky!!!!! To find it, locate the cup of the Big Dipper to the handle of the Little dipper. It doesn’t appear to move in the night sky but the other stars rotate around it North pole and Polaris are about 1° off from one another

Earth’s Orbital Motion Precession: rotation of Earth’s axis itself; makes one complete circle in about 26,000 years Figure 1-19a. Caption: Precession. (a) Earth’s axis currently points nearly toward the star Polaris. About 12,000 years from now—almost halfway through one cycle of precession—Earth’s axis will point toward a star called Vega, which will then be the “North Star.” Five thousand years ago, the North Star was a star named Thuban in the constellation Draco.

Precession Wobbles in a 26,000 year cycle Wobble is between Polaris, Vega and Thuban Changes the position of the Vernal Equinox which will also change the co-ordinates of the stars

1.4 Earth’s Orbital Motion Time for Earth to orbit once around Sun, relative to fixed stars, is sidereal year Tropical year follows seasons; sidereal year follows constellations—in 13,000 years July and August will still be summer, but Orion will be a summer constellation

On your white board Draw the moon phases and label the names of the phases as best as you know them.

Motion of the Moon Moon takes about 29.5 days to go through whole cycle of phases—synodic month Phases are due to different amounts of sunlit portion being visible from Earth Time to make full 360° rotation around Earth, sidereal month, is about 2 days shorter Figure 1-20. Caption: Lunar Phases. Because the Moon orbits Earth, the visible fraction of the lunar sunlit face varies from night to night, although the Moon always keeps the same face toward our planet. (Note the location of the small, straight arrows, which mark the same point on the lunar surface at each phase shown.) The complete cycle of lunar phases, shown here starting at the waxing crescent phase and following the Moon’s orbit counterclockwise, takes 29.5 days to complete. Rising and setting times for some phases are also indicated. (UC/Lick Observatory)

Go to moon phases powerpoint!!

White board: With a partner draw a lunar eclipse and a solar eclipse

Motion of the Moon Eclipses occur when Earth, Moon, and Sun form a straight line Figure 1-26a. Caption: Eclipse Geometry. (a) An eclipse occurs when Earth, Moon, and Sun are precisely aligned. If the Moon’s orbital plane lay in exactly the plane of the ecliptic, this alignment would occur once a month. However, the Moon’s orbit is inclined at about 5° to the ecliptic, so not all configurations are favorable for producing an eclipse.

Motion of the Moon Lunar eclipse: Earth is between Moon and Sun Partial when only part of Moon is in shadow Total when it all is in shadow Figure 1-22. Caption: Lunar Eclipse. A lunar eclipse occurs when the Moon passes through Earth’s shadow. At these times, we see a darkened, copper-colored Moon, as shown by the partial eclipse in the inset photograph. The red coloration is caused by sunlight deflected by Earth’s atmosphere onto the Moon’s surface. An observer on the Moon would see Earth surrounded by a bright, but narrow, ring of orange sunlight. Note that this figure is not drawn to scale, and only Earth’s umbra (see text and Figure 1.24) is shown. (Inset: G. Schneider)

Motion of the Moon Solar eclipse: Moon is between Earth and Sun Partial when only part of Sun is blocked Total when it all is blocked Annular when Moon is too far from Earth for total Figure 1-24. Caption: Types of Solar Eclipse. (a) The Moon’s shadow consists of two parts: the umbra, where no sunlight is seen, and the penumbra, where a portion of the Sun is visible. (b) If we are in the umbra, we see a total eclipse; in the penumbra, we see a partial eclipse. (c) If the Moon is too far from Earth at the moment of the eclipse, the umbra does not reach Earth and there is no region of totality; instead, an annular eclipse is seen. (Note that these figures are not drawn to scale.) (Insets: NOAA; G. Schneider)

Motion of the Moon Eclipses don’t occur every month because Earth’s and Moon’s orbits are not in the same plane Figure 1-28b. Caption: Eclipse Geometry. (b) For an eclipse to occur, the line of intersection of the two planes must lie along the Earth–Sun line. Thus, eclipses can occur just at specific times of the year. Only the umbra of each shadow is shown, for clarity (see Figure 1.24).