Subj : Daily APOD Report To : All From : Ben Ritchey Date : Wed Sep 12 2018 11:29:27 Astronomy Picture of the Day Astronomy Picture of the Day Discover the cosmos! [1] Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2018 September 12 Lunations Video Credit: Data: Lunar Reconnaissance Orbiter [2] ; Animation: NASA [3] 's Scientific Visualization Studio [4] ; Music: The Blue Danube [5] (Johann Strauss II [6] ) Explanation: Our Moon's appearance changes nightly. As the Moon [7] orbits the Earth [8] , the half illuminated by the Sun [9] first becomes increasingly visible, then decreasingly visible. The featured video [10] animates images taken by NASA's Moon-orbiting Lunar Reconnaissance Orbiter [11] to show all 12 lunations that appear this year, 2018. A single lunation [12] describes one full cycle of our Moon, including all of its phases [13] . A full lunation [14] takes about 29.5 days, just under a month ( moon-th [15] ). As each lunation [16] progresses, sunlight reflects from the Moon [17] at different angles, and so illuminates different [18] features differently. During all of this, of course, the Moon [19] always keeps the same face toward the Earth [20] . What is less apparent night-to-night is that the Moon [21] 's apparent size changes slightly, and that a slight wobble called a libration [22] occurs as the Moon [23] progresses along its elliptical orbit [24] . Tomorrow's picture: open space ------------------------------------------------------------------------------- < [25] | Archive [26] | Submissions [27] | Index [28] | Search [29] | Calendar [30] | RSS [31] | Education [32] | About APOD [33] | Discuss [34] | > [35] ------------------------------------------------------------------------------- Authors & editors: Robert Nemiroff [36] (MTU [37] ) & Jerry Bonnell [38] (UMCP [39] ) NASA Official: Phillip Newman Specific rights apply [40] . NASA Web Privacy Policy and Important Notices [41] A service of: ASD [42] at NASA [43] / GSFC [44] & Michigan Tech. U. [45] ---------- Site notes: [1] archivepix.html [2] https://lunar.gsfc.nasa.gov/ [3] https://www.nasa.gov/ [4] https://svs.gsfc.nasa.gov/ [5] https://en.wikipedia.org/wiki/The_Blue_Danube [6] https://en.wikipedia.org/wiki/Johann_Strauss_II [7] https://solarsystem.nasa.gov/moons/earths-moon/overview/ [8] ap070325.html [9] http://en.wikipedia.org/wiki/Sun [10] https://svs.gsfc.nasa.gov/4604 [11] https://lunar.gsfc.nasa.gov/about.html [12] http://en.wikipedia.org/wiki/Lunation [13] https://spaceplace.nasa.gov/review/dr-marc-earth/Moon_phases_drawing.gif [14] http://www.inconstantmoon.com/not_phas.htm [15] https://www.phrases.org.uk/bulletin_board/11/messages/229.html [16] http://scienceworld.wolfram.com/astronomy/Lunation.html [17] moon.html [18] ap180522.html [19] http://en.wikipedia.org/wiki/Moon [20] ap171204.html [21] http://www.astronomycafe.net/qadir/amoonm.html [22] http://en.wikipedia.org/wiki/Libration [23] ap180318.html [24] http://galileoandeinstein.physics.virginia.edu/more_stuff/flashlets/kepler6.htm [25] ap180911.html [26] archivepix.html [27] lib/apsubmit2015.html [28] lib/aptree.html [29] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search [30] calendar/allyears.html [31] /apod.rss [32] lib/edlinks.html [33] lib/about_apod.html [34] http://asterisk.apod.com/discuss_apod.php?date=180912 [35] ap180913.html [36] http://www.phy.mtu.edu/faculty/Nemiroff.html [37] http://www.phy.mtu.edu/ [38] https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html [39] http://www.astro.umd.edu/ [40] lib/about_apod.html#srapply [41] https://www.nasa.gov/about/highlights/HP_Privacy.html [42] https://astrophysics.gsfc.nasa.gov/ [43] https://www.nasa.gov/ [44] https://www.nasa.gov/centers/goddard/ [45] http://www.mtu.edu/ --- Mystic BBS v1.12 A39 (Windows/32) * Origin: FIDONet - The Positronium Repository (1:393/68) .