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. 2023 February 9 [2]See Explanation. Clicking on the picture will download the highest resolution version available. Nacreous Clouds over Lapland Image Credit & [3]Copyright: [4]Dennis Lehtonen Explanation: Vivid and lustrous, wafting iridescent waves of color wash across this skyscape from Kilpisjärvi, Finland. [5]Known as nacreous clouds or mother-of-pearl clouds, they are rare. But their [6]unforgettable appearance was captured looking south at 69 degrees north latitude at sunset on January 24. A type of [7]polar stratospheric cloud, they form when unusually cold temperatures in the usually cloudless [8]lower stratosphere form ice crystals. Still sunlit at altitudes of around 15 to 25 kilometers, the clouds can diffract sunlight even after sunset and just before the dawn. Tomorrow's picture: pixels in space __________________________________________________________________ [9]< | [10]Archive | [11]Submissions | [12]Index | [13]Search | [14]Calendar | [15]RSS | [16]Education | [17]About APOD | [18]Discuss | [19]> __________________________________________________________________ Authors & editors: [20]Robert Nemiroff ([21]MTU) & [22]Jerry Bonnell ([23]UMCP) NASA Official: Phillip Newman [24]Specific rights apply. [25]NASA Web Privacy Policy and Important Notices A service of: [26]ASD at [27]NASA / [28]GSFC, [29]NASA Science Activation & [30]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2302/PearlCloudDennis7.jpg 3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 4. https://www.instagram.com/astrodenniina/ 5. https://www.atoptics.co.uk/highsky/nacr1.htm 6. https://ui.adsabs.harvard.edu/abs/2018BAMS...99.1377P/abstract 7. https://www.nasa.gov/multimedia/imagegallery/image_feature_680.html 8. https://www.atoptics.co.uk/highsky/htrop.htm 9. https://apod.nasa.gov/apod/ap230208.html 10. https://apod.nasa.gov/apod/archivepix.html 11. https://apod.nasa.gov/apod/lib/apsubmit2015.html 12. https://apod.nasa.gov/apod/lib/aptree.html 13. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 14. https://apod.nasa.gov/apod/calendar/allyears.html 15. https://apod.nasa.gov/apod.rss 16. https://apod.nasa.gov/apod/lib/edlinks.html 17. https://apod.nasa.gov/apod/lib/about_apod.html 18. http://asterisk.apod.com/discuss_apod.php?date=230209 19. https://apod.nasa.gov/apod/ap230210.html 20. http://www.phy.mtu.edu/faculty/Nemiroff.html 21. http://www.phy.mtu.edu/ 22. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 23. http://www.astro.umd.edu/ 24. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 25. https://www.nasa.gov/about/highlights/HP_Privacy.html 26. https://astrophysics.gsfc.nasa.gov/ 27. https://www.nasa.gov/ 28. https://www.nasa.gov/centers/goddard/ 29. https://science.nasa.gov/learners 30. http://www.mtu.edu/