AST 165 Lecture Notes - Lecture 6: Capricornus, Ecliptic, Leap Years
Document Summary
Based off ecliptic path when sun passes through each. As earth orbits sun, sun moves through different constellations. 13th constellation: ophiuchus; ditched because astronomers based them off 12 months. Ecliptic: path sun follows on celestial sphere. What constellations we can see at night depends on time of. As earth orbits sun every 365 days, its direction when facing away is diff depending on time of year. Zodiac: 12 traditional constellations (13 w ophiucus) along ecliptic where sun appears to be located at some time during year. Face opposite during winter/summer-- so we see diff stars depending on where we face. During winter: summer constellations gone bc they"re up when sun is up. During summer: winter constellations gone bc they"re up when sun is up. Earth rotates around axis every 24 hrs, while axis precesses. Tropical year: 365. 24 days (1 complete orbit) Common year: 365 days ( short of tropical year)
