The Night Sky What are constellations? Why do we see some in winter, some in summer and some all year long? Why do they move? How are they useful?

The most simplest observation in Astronomy: Look at the night sky About 3000 stars visible at any one time; distributed randomly but human brain tends to find patterns… These patterns are constellations

Group stars into constellations: figures having meaning to those doing the grouping Useful: Polaris, which is almost due north Served as markers Daily and yearly rhythms

The Night Sky Motion of stars caused by Earth’s rotation As Earth spins, we are carried beneath the sky so that the stars move from east to west

VLT Night Sky Time lapse http://www.youtube.com/watch?v=wFpeM3fxJoQ

The Night Sky Watch the sky over a year, notice each season has its own constellations Orion- January Leo- March Scorpios- June Tells Time of Year

Astrology NOT Astronomy Pseudo-science which claims that the positions of the heavenly bodies have an effect on the lives of human beings and events on Earth.

Why do we see some constellations in winter, some in summer and some all year long? Results from our planet’s orbital motion around the Sun Different parts of sky become visible Sun’s glare

Why do the Stars Move? There are five constellations that we consider as being circumpolar. We have seperated them into two groups. Group 1: Ursa Major, Ursa Minor, Draco Group 2: Cassiopeia, Cepheus

Why do the Stars Move? The Stars don’t actually move… It is the Earth that is moving (spinning). The spinning Earth gives the perception that the stars move. Polaris – Earth’s northern axis points at this star so its movement is not affected by Earth’s Rotation.

How are Constellations Useful? Finding N, S, E & West Find Big Dipper… then follow end stars over to Polaris (the North Star) Track your position on Earth (navigation) What about the 5 wanderers?

The 5 Wanderers 5 Planets Four of which are easily visible without a telescope. They are Mercury, Venus, Mars, Jupiter, and Saturn. Mercury is more difficult to see due to its proximity to the Sun.

The Night Sky http://www.youtube.com/watch?v=lWFyRA9FR1E&feature=c4-overview&list=UUqvjEkH_41m4DYaoNQwk4Bw

Because of orbital motion of the planets around the sun, planets move across the sky at different speeds than stars Always rise in east and set in the west, orbital motion of the planets usually shift eastward in respect to the stars Watch the night sky, focus on a planet and a star near it in the sky, planet moves slightly slower

Planet may shift westward through the constellations Caused by Earth’s motion Over a couple of nights Car moving backward as pass

Eclipse Lunar Eclipse Solar Eclipse Earth’s shadow strikes the moon only at full moon Solar Eclipse Moon’s shadow strikes the Earth

Eclipse Next Lunar Eclipse: Oct 18, 2013 Next Solar Eclipse: Nov 3, 2013

http://www.youtube.com/watch?v=wuhNZejHeBg

What is an eclipse? Blockage of light from astronomical body caused by the passage of another body between it and the observer

Zodiac A band running across the celestial sphere in which the planets move

Apparent Motion vs. Retrograde Motion Apparent Motion: movement of any body in space actually caused by Earth’s revolution or rotation Retrograde Motion: movement in which a planet moves forward, then backward, then forward again as observed from Earth