The North Celestial Pole (NCP) • Special spot on the sky that the Earth’s rotation axis points to • Why special? During the night the stars appear to rotate around this spot • Also special (and useful) in other ways …
Big Dipper: Points to Polaris • http://www.astropix.com/HTML/C_SPRING/URSAS.HTM
Lucky Breaks! • The star Polaris is amazing close to NCP (now) • The “pointer stars” in the Big Dipper line up directly with Polaris!!!! • Big Dipper is circumpolar constellation • See it all night and all year • Polaris also called Pole Star, North Star
Why care about finding Polaris? • The direction of Polaris is due North • The angle between Polaris and the horizon is YOUR LATITUDE • How can I measure angles?
Astronomy Picture of the Day (APOD) http://antwrp.gsfc.nasa.gov/apod/ap090627.html • Summer Triangle • http://antwrp.gsfc.nasa.gov/apod/ap090912.html • Winter Hexagon • http://antwrp.gsfc.nasa.gov/apod/ap021106.html
Constellation Facts • Group of stars all in roughly the same direction from Earth, BUT …. Each has its own different distance from the Earth • Therefore, NOT grouped together is space • From Greek astronomers have inherited the names of the constellations: mythological figures or animals • Different cultures on Earth each have different names for the constellations
Visible Constellations change over a year • May have heard … • “Orion is a winter constellation” • “You can see Cygnus most of the summer” • Above comments arise because you cannot see the Constellations near where the Sun is in the sky • Sun so bright it washes out rest of stars • Since Sun moves along the Ecliptic over a year the constellations “away” from the Sun change over a year.
The Zodiac • Band of constellations closest to the Ecliptic (Sun’s yearly path across the sky) • Correspond to Horoscope “Signs” • Astrology used to make predictions (not science!) • Useful for backyard astronomy: Planets and the Moon can always be found in the Zodiac • Width of the Zodiac belt ~ 18°
Mars Saturn Mercury
Naming Stars Brightest star in constellation Taurus Greek name: α Taurus Arabic name: Aldebaran “Al Debarren” “The Follower” (of the Pleiades)