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. 2025 December 19 [2]See Explanation. Clicking on the picture will download the highest resolution version available. Long Shadows of the Montes Caucasus Image Credit & [3]Copyright: Guy Bardon Explanation: [4]When the Moon is at its first quarter phase, the Sun rises along the [5]Montes Caucasus as seen from the lunar surface. The lunar mountain range casts the magnificent, spire-like shadows in this telescopic view from planet Earth, looking along the lunar terminator or the boundary between lunar night and day. Named for Earth's own Caucasus Mountains, the rugged lunar [6]Montes Caucasus peaks, up to 6 kilometers high, are located between the smooth Mare Imbrium to the west and Mare Serenitatis to the east. Still mostly in shadow in this first quarter [7]lunarscape, at the left (west) impact craters reflect the light of the rising Sun along their outer, eastern crater walls. Tomorrow's picture: the Sun's tattoo __________________________________________________________________ [8]< | [9]Archive | [10]Submissions | [11]Index | [12]Search | [13]Calendar | [14]RSS | [15]Education | [16]About APOD | [17]Discuss | [18]> __________________________________________________________________ Authors & editors: [19]Robert Nemiroff ([20]MTU) & [21]Jerry Bonnell ([22]UMCP) NASA Official: Amber Straughn [23]Specific rights apply. [24]NASA Web Privacy, [25]Accessibility, [26]Notices; A service of: [27]ASD at [28]NASA / [29]GSFC, [30]NASA Science Activation & [31]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2512/MontesCaucasusCopie.png 3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 4. https://science.nasa.gov/moon/moon-phases/ 5. https://en.wikipedia.org/wiki/Montes_Caucasus 6. https://planetarynames.wr.usgs.gov/Feature/4007 7. https://www.vaticanobservatory.org/sacred-space-astronomy/caucasus-triangle/ 8. https://apod.nasa.gov/apod/ap251218.html 9. https://apod.nasa.gov/apod/archivepix.html 10. https://apod.nasa.gov/apod/lib/apsubmit2015.html 11. https://apod.nasa.gov/apod/lib/aptree.html 12. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 13. https://apod.nasa.gov/apod/calendar/allyears.html 14. https://apod.com/feed.rss 15. https://apod.nasa.gov/apod/lib/edlinks.html 16. https://apod.nasa.gov/apod/lib/about_apod.html 17. https://asterisk.apod.com/discuss_apod.php?date=251219 18. https://apod.nasa.gov/apod/ap251220.html 19. http://www.phy.mtu.edu/faculty/Nemiroff.html 20. http://www.phy.mtu.edu/ 21. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 22. http://www.astro.umd.edu/ 23. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 24. https://www.nasa.gov/about/highlights/HP_Privacy.html 25. https://www.nasa.gov/general/accessibility/ 26. https://www.nasa.gov/privacy/ 27. https://astrophysics.gsfc.nasa.gov/ 28. https://www.nasa.gov/ 29. https://www.nasa.gov/centers/goddard/ 30. https://science.nasa.gov/learners 31. http://www.mtu.edu/