﻿ 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 August 30 [2]The picture shows a solar circumhorizontal arc -- nicknamed a fire rainbow -- over West Virgina, USA. Please see the explanation for more detailed information. A Fire Rainbow over West Virginia Image Credit: [3]Christa Harbig Explanation: What's happening to this cloud? Ice crystals in a distant cirrus cloud are acting like little floating [4]prisms. Known informally as a fire rainbow for its flame-like appearance, a [5]circumhorizon arc appears parallel to the horizon. For a [6]circumhorizontal arc to be visible, [7]the Sun must be at least 58 degrees high in a sky where [8]cirrus clouds present below -- in this case [9]cirrus fibrates. The numerous, flat, [10]hexagonal ice-crystals that compose the [11]cirrus cloud must be [12]aligned horizontally to properly [13]refract sunlight in a collectively similar manner. Therefore, [14]circumhorizontal [15]arcs are [16]somewhat unusual to see. The [17]featured fire rainbow was photographed earlier this month near [18]North Fork Mountain in [19]West Virginia, [20]USA. Tomorrow's picture: true moon blue __________________________________________________________________ [21]< | [22]Archive | [23]Submissions | [24]Index | [25]Search | [26]Calendar | [27]RSS | [28]Education | [29]About APOD | [30]Discuss | [31]> __________________________________________________________________ Authors & editors: [32]Robert Nemiroff ([33]MTU) & [34]Jerry Bonnell ([35]UMCP) NASA Official: Phillip Newman [36]Specific rights apply. [37]NASA Web Privacy Policy and Important Notices A service of: [38]ASD at [39]NASA / [40]GSFC & [41]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2108/FireRainbow_Harbig_4000.jpg 3. https://www.facebook.com/christa.harbig.photos/ 4. http://micro.magnet.fsu.edu/primer/java/scienceopticsu/newton/ 5. https://en.wikipedia.org/wiki/Circumhorizon_arc 6. https://www.atoptics.co.uk/halo/cha2.htm 7. https://solarsystem.nasa.gov/solar-system/sun/overview/ 8. https://en.wikipedia.org/wiki/Cirrus_cloud 9. https://www.colweather.org.uk/gal-clouds-cirrus.php#Cirrus fibratus 10. http://www.atoptics.co.uk/halo/orplate.htm 11. https://en.wikipedia.org/wiki/Cirrus_cloud 12. https://www.atoptics.co.uk/halo/platcol.htm 13. http://youtube.com/watch?v=U98KPM2b9IA 14. https://apod.nasa.gov/apod/ap190519.html 15. https://apod.nasa.gov/apod/ap151215.html 16. https://i.pinimg.com/550x/81/21/c0/8121c0291fa14d1fe52b9eb007741cac.jpg 17. https://www.facebook.com/photo?fbid=4794142133932422 18. https://youtu.be/kROh8JwKnOk 19. https://en.wikipedia.org/wiki/West_Virginia 20. https://en.wikipedia.org/wiki/United_States 21. https://apod.nasa.gov/apod/ap210829.html 22. https://apod.nasa.gov/apod/archivepix.html 23. https://apod.nasa.gov/apod/lib/apsubmit2015.html 24. https://apod.nasa.gov/apod/lib/aptree.html 25. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 26. https://apod.nasa.gov/apod/calendar/allyears.html 27. https://apod.nasa.gov/apod.rss 28. https://apod.nasa.gov/apod/lib/edlinks.html 29. https://apod.nasa.gov/apod/lib/about_apod.html 30. http://asterisk.apod.com/discuss_apod.php?date=210830 31. https://apod.nasa.gov/apod/ap210831.html 32. http://www.phy.mtu.edu/faculty/Nemiroff.html 33. http://www.phy.mtu.edu/ 34. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 35. http://www.astro.umd.edu/ 36. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 37. https://www.nasa.gov/about/highlights/HP_Privacy.html 38. https://astrophysics.gsfc.nasa.gov/ 39. https://www.nasa.gov/ 40. https://www.nasa.gov/centers/goddard/ 41. http://www.mtu.edu/