¿ Astronomy Picture of the Day [1]Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2021 January 11 IFRAME: [2]https://www.youtube.com/embed/8XV2-pmiyAg?rel=0 Moon Phases in 2021 Video Credit: Data: [3]Lunar Reconnaissance Orbiter ; Animation: [4]NASA's [5]Scientific Visualization Studio; Music: [6]Brandenburg Concerto No4-1 BWV1049 ([7]Johann Sebastian Bach), by [8]Kevin MacLeod via [9]Incompetech Explanation: What will the Moon phase be on your birthday this year? It is [10]hard to predict because the [11]Moon's appearance changes nightly. As the [12]Moon orbits the [13]Earth, the half illuminated by the [14]Sun first becomes increasingly visible, then decreasingly visible. The [15]featured video animates images taken by NASA's Moon-orbiting [16]Lunar Reconnaissance Orbiter to show all 12 lunations that appear this year, 2021. A single [17]lunation describes one full cycle of our Moon, including all of its [18]phases. A full [19]lunation takes about 29.5 days, just under a month ([20]moon-th). As each [21]lunation progresses, sunlight reflects from the [22]Moon at different angles, and so [23]illuminates different features differently. During all of this, of course, the [24]Moon always keeps the same face toward the [25]Earth. What is less apparent night-to-night is that the [26]Moon's apparent size changes slightly, and that a slight wobble called a [27]libration occurs as the [28]Moon progresses along its [29]elliptical orbit. APOD online webinar January 12: [30]Free registration, hosted by Amateur Astronomers Association of New York. Tomorrow's picture: folklore sky __________________________________________________________________ [31]< | [32]Archive | [33]Submissions | [34]Index | [35]Search | [36]Calendar | [37]RSS | [38]Education | [39]About APOD | [40]Discuss | [41]> __________________________________________________________________ Authors & editors: [42]Robert Nemiroff ([43]MTU) & [44]Jerry Bonnell ([45]UMCP) NASA Official: Phillip Newman [46]Specific rights apply. [47]NASA Web Privacy Policy and Important Notices A service of: [48]ASD at [49]NASA / [50]GSFC & [51]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://www.youtube.com/embed/8XV2-pmiyAg?rel=0 3. https://lunar.gsfc.nasa.gov/ 4. https://www.nasa.gov/ 5. https://svs.gsfc.nasa.gov/ 6. https://en.wikipedia.org/wiki/Brandenburg_Concertos#No._4_in_G_major,_BWV_1049 7. https://en.wikipedia.org/wiki/Johann_Sebastian_Bach 8. https://incompetech.com/email.html 9. https://incompetech.com/ 10. https://vcahospitals.com/-/media/vca/images/lifelearn-images-foldered/10812/cognition2.jpg?la=en&hash=69D0BDA985281F5E7A93F87A8B783C90 11. https://apod.nasa.gov/apod/ap160201.html 12. https://solarsystem.nasa.gov/moons/earths-moon/overview/ 13. https://apod.nasa.gov/apod/ap070325.html 14. https://en.wikipedia.org/wiki/Sun 15. https://svs.gsfc.nasa.gov/4874 16. https://lunar.gsfc.nasa.gov/about.html 17. https://en.wikipedia.org/wiki/Lunation 18. https://spaceplace.nasa.gov/review/dr-marc-earth/Moon_phases_drawing.gif 19. http://www.inconstantmoon.com/not_phas.htm 20. https://www.phrases.org.uk/bulletin_board/11/messages/229.html 21. https://scienceworld.wolfram.com/astronomy/Lunation.html 22. https://apod.nasa.gov/apod/moon.html 23. https://apod.nasa.gov/apod/ap180522.html 24. https://en.wikipedia.org/wiki/Moon 25. https://apod.nasa.gov/apod/ap171204.html 26. http://www.astronomycafe.net/qadir/amoonm.html 27. https://en.wikipedia.org/wiki/Libration 28. https://apod.nasa.gov/apod/ap180318.html 29. http://galileoandeinstein.phys.virginia.edu/more_stuff/Applets/Kepler/kepler.html 30. https://members.aaa.org/event-4087594 31. https://apod.nasa.gov/apod/ap210110.html 32. https://apod.nasa.gov/apod/archivepix.html 33. https://apod.nasa.gov/apod/lib/apsubmit2015.html 34. https://apod.nasa.gov/apod/lib/aptree.html 35. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 36. https://apod.nasa.gov/apod/calendar/allyears.html 37. https://apod.nasa.gov/apod.rss 38. https://apod.nasa.gov/apod/lib/edlinks.html 39. https://apod.nasa.gov/apod/lib/about_apod.html 40. http://asterisk.apod.com/discuss_apod.php?date=210111 41. https://apod.nasa.gov/apod/ap210112.html 42. http://www.phy.mtu.edu/faculty/Nemiroff.html 43. http://www.phy.mtu.edu/ 44. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 45. http://www.astro.umd.edu/ 46. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 47. https://www.nasa.gov/about/highlights/HP_Privacy.html 48. https://astrophysics.gsfc.nasa.gov/ 49. https://www.nasa.gov/ 50. https://www.nasa.gov/centers/goddard/ 51. http://www.mtu.edu/