310 likes | 431 Vues
Finding Your Way In The Sky. The Big Dipper. Directions in the Sky. North is toward the North Celestial Pole South is toward the South Celestial Pole East is toward East on the ground (usually) West is toward West on the ground (usually) On a ground map you’re outside a sphere looking in.
E N D
Directions in the Sky • North is toward the North Celestial Pole • South is toward the South Celestial Pole • East is toward East on the ground (usually) • West is toward West on the ground (usually) • On a ground map you’re outside a sphere looking in. • On sky maps you’re inside a sphere looking out. • East and West on star maps are reversed compared to maps of the ground
Stars and Constellations • Many proper star names are Arabic • Catalog labels also used (Alpha Centauri) • Constellation names are Latin • Ancient groups from Near Eastern myths via Greeks • Numerous 17th-18th Century inventions • 89 Constellations • Fixed boundaries in sky • Every star is in one, and only one, constellation • There is no “official” way to draw constellations
About Constellation Names • Latin uses word endings where we often use prepositions (Compare English ‘s) • Possessive form different from normal form • Centaurusbut Alpha Centauri • Andromeda but Alpha Andromedae • Gemini – Geminorum • Virgo – Virginis • Orion – Orionis • Ursa Major – UrsaeMajoris
Recognizing Constellations • They change location • They change times they are visible • They change orientation • Best strategy: Learn shapes and relative locations • Different books use slightly different figures. Use whatever works for you
Stars Vary in Brightness and Color • 1st Magnitude = Very Bright • 2nd Magnitude = Polaris, Big Dipper • 3rd Magnitude = Fairly obvious • 4th Magnitude = Moderately Faint • 5th Magnitude = Faint • 6th Magnitude = Barely visible • Colors range from reddish through yellow to white and blue-white. Colors are subtle