Download Astronomy 120: Lecture 6 - The Phases and Orbit of the Moon and more Assignments Astronomy in PDF only on Docsity! Astro 120 Fall 2005: Lecture 6 page 1 • The Phases of the Moon • new->waxing->1st Q->Full->waning->3rd Q-> new • where in the sky can you find a _______ moon? • lunar rotation - once per month - keeps the same face pointing towards Earth • The Moon’s Orbit • tilted 5o to the ecliptic • intersects ecliptic at two nodes (ascen’g, descen’g) • eclipses possible only when moon is at a node Brief review of last time: The Phases of the Moon Reading: Bennett, Chapter 2, Section 2.6 Chapter 3, Sections 3.1-3.5 Help Room: Now Open - Schedule on website Problem Set #1: Available NOW on the Astro 120 Website; Due 9/9-12 Print from your browser! Astro 120 Fall 2005: Lecture 5 page 2 Appearance of Moon from Earth Phase crossesmeridian appearance New Moon noon waxing crescent 1st quarter sunset waxing gibbous Full Moon midnight waning gibbous 3rd quarter sunrise waning crescent Astro 120 Fall 2005: Lecture 6 page 3 What is the phase of the moon in this picture? What time of day was this picture taken? WestSouth Astro 120 Fall 2005: Lecture 5 page 4 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 2005: Lecture 6 page 5 Need the Sun to lie at a node at new or full moon for an eclipse to occur Astro 120 Fall 2005: Lecture 5 page 6 Regression of the line of nodes: Line of nodes circles WESTWARDS in 18.7 years: Highest/Lowest Moon 9.35 years later: smallest lunar altitude variation ad d a Astro 120 Fall 2005: Lecture 6 page 7 Earth and Moon Shadows • The UMBRA - region of total obscuration of Sun • narrow, cone-shaped • finite length • The PENUMBRA - region of partial obscuration of sun • broadening cone-shaped • “infinite” length umbra penumbra moon or Earth Astro 120 Fall 2005: Lecture 6 page 8 • Moon passes through Earth’s shadow • total • partial • penumbral • visible whenever the moon is above horizon • duration up to 1.5 hours (total) and 3 hours (partial) Circumstances of a Lunar Eclipse Earth s umbra penumbra view from Earth Earth s shadow at Moon s distance Moon s path Partial Total Penumbral
