Have you ever seen a halo around the Sun? This fairly common sight occurs when high thin clouds [ http://ww2010.atmos. uiuc.edu/(Gh)/wwhlpr /cirrus.rxml?hret=/g uides/mtr/opt/ice/ha lo/22.rxml ] containing millions of tiny ice crystals [
http://www.sundog.c…] cover much of the sky. Each ice crystal [
http://en.wikipedia…] acts like a miniature lens. Because most [
http://www.sundog.c…] of the crystals have a similar elongated hexagonal shape, light entering one crystal face and exiting through the opposing face refracts 22 degrees [
http://mintaka.sdsu…], which corresponds to the radius of the Sun Halo [ http://ww2010.atmos. uiuc.edu/(Gh)/guides /mtr/opt/ice/halo/22 .rxml ]. A similar Moon Halo [
http://antwrp.gsfc.…] may be visible during the night. The picture was taken in Gunlock, Utah [
http://en.wikipedia…], USA [
http://www.cia.gov/…]. A flock of birds [
http://www.straight…] was caught by chance in the foreground. Exactly how ice-crystals form [
http://www.its.calt…] in clouds remains under investigation [
http://adsabs.harva…].
Explanation
Have you ever seen a halo around the Sun? This fairly common sight occurs when high thin clouds [ http://ww2010.atmos. uiuc.edu/(Gh)/wwhlpr /cirrus.rxml?hret=/g uides/mtr/opt/ice/ha lo/22.rxml ] containing millions of tiny ice crystals [
http://www.sundog.c…] cover much of the sky. Each ice crystal [
http://en.wikipedia…] acts like a miniature lens. Because most [
http://www.sundog.c…] of the crystals have a similar elongated hexagonal shape, light entering one crystal face and exiting through the opposing face refracts 22 degrees [
http://mintaka.sdsu…], which corresponds to the radius of the Sun Halo [ http://ww2010.atmos. uiuc.edu/(Gh)/guides /mtr/opt/ice/halo/22 .rxml ]. A similar Moon Halo [
http://antwrp.gsfc.…] may be visible during the night. The picture was taken in Gunlock, Utah [
http://en.wikipedia…], USA [
http://www.cia.gov/…]. A flock of birds [
http://www.straight…] was caught by chance in the foreground. Exactly how ice-crystals form [
http://www.its.calt…] in clouds remains under investigation [
http://adsabs.harva…].
Explanation
