* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Introduction to Astronomy
History of astronomy wikipedia , lookup
Copernican heliocentrism wikipedia , lookup
Chinese astronomy wikipedia , lookup
Aquarius (constellation) wikipedia , lookup
Astronomical unit wikipedia , lookup
History of Solar System formation and evolution hypotheses wikipedia , lookup
Formation and evolution of the Solar System wikipedia , lookup
Corvus (constellation) wikipedia , lookup
Equation of time wikipedia , lookup
Extraterrestrial skies wikipedia , lookup
Solar System wikipedia , lookup
Archaeoastronomy wikipedia , lookup
Dialogue Concerning the Two Chief World Systems wikipedia , lookup
Geocentric model wikipedia , lookup
Stellar kinematics wikipedia , lookup
Hebrew astronomy wikipedia , lookup
Tropical year wikipedia , lookup
Miscellaneous announcements… • Homework 1 due today by 5:00. • Pick up Homework 2; solutions are on the web. • Get started on a project soon, if you haven’t already! • Astrophotographers: please see me after class. • Questions on motion of the stars? • Try out Sky View Café and/or Sky Chart III… The Sun and the Seasons 6 September 2006 Today: • Measuring angles in the sky • How the sun moves through our sky • Seasons Measuring Angles Motion of the Sun • On any given day, the sun’s motion is essentially the same as that of a star (rises in the east, sets in the west). • The sun’s motion doesn’t quite keep up with the stars: It completes a 360º circle in 24 hours. • With respect to the stars, the sun appears to move once a year around a great circle, tipped 23.5º with respect to the celestial equator. • In late June (summer solstice), the sun is farthest north; in late December (winter solstice), the sun is farthest south. In late March and September (equinoxes), it’s on the celestial equator. Motion of the Sun Facing south Motion of the Sun Sun’s apparent path among the stars is called the ecliptic Seasons Summer Winter (A one-square-meter surface, directly facing the sun, receives about 1000 watts of power.)