Astro 120 Lecture 5: The Ecliptic, Seasons, Phases of the Moon, and Lunar Eclipses, Assignments of Astronomy

Download Astro 120 Lecture 5: The Ecliptic, Seasons, Phases of the Moon, and Lunar Eclipses and more Assignments Astronomy in PDF only on Docsity! Astro 120 Fall 2008: Lecture 5 page 1 • The Ecliptic • sun moves eastward along the ecliptic • inclination of the ecliptic = 23.5 degrees to celestial equator • crossing points are equinoxes; extrema are solstices • The Seasons • azimuth of sunrise/sunset at various latitudes • length of time above the horizon in summer and winter • angle of sunlight shallower in winter than in summer • distance is NOT a factor • The Motion of the Moon • eastward motion in orbit around the Earth • Sidereal vs. synodic month • The Phases of the Moon Brief review of last time: Time and The Seasons Reading: Bennett, Chapter 2, Sections 2.3 Problem Set #2: !Available NOW on the Astro 120 Website; Due 9/12(15) ! ! ! ! ! ! Print from your browser! Astro 120 Fall 2008: Lecture 5 page 2 http://antwrp.gsfc.nasa.gov/apod/ap070709.html http://www.ascensionrecta.com/galeriasol.htm Astro 120 Fall 2008: Lecture 5 page 3 Astro 120 Fall 2008: Lecture 5 page 4 The Phases of the Moon 6PM 6AM noonmidn!t newFull 1st Quarter 3rd Quarter CRESCENT GIBBOUS GIBBOUS CRESCENT Waning Waxing Astro 120 Fall 2008: Lecture 5 page 5 Appearance of Moon from Earth Phase crosses meridian appearance New Moon noon waxing crescent 1st quarter sunset waxing gibbous Full Moon midnight waning gibbous 3rd quarter sunrise waning crescent Astro 120 Fall 2008: Lecture 5 page 6 The Moon’s Orbit is Tilted! why not ECLIPSES every new and full moon? The Moon!s orbit is tilted 5o to the ecliptic 23.5 ecliptic Nodes: ! crossing points of lunar ! orbit with ecliptic Line of Nodes: ! connects lunar nodes Astro 120 Fall 2008: Lecture 5 page 7 Need the Sun to lie at a node at new or full moon for an eclipse to occur Astro 120 Fall 2008: Lecture 5 page 8 Regression of the line of nodes: Line of nodes circles WESTWARDS in 18.7 years (caused by “torquing” effect of the Sun): Highest/Lowest Moon 9.35 years later: smallest lunar altitude variation a d d a