Noctilucent cloud. These bright displays are seen in the middle of the night in summer at high latitudes. Seen here is an unusual crossed pattern,known as the "herring" structure. The composition of noctilucent clouds is unknown,but they are known to exist at 70-90 kilometres altitude - well above normal clouds. They are normally seen when the sun is 4-16 degrees below the observer's horizon,and have a whitish colour against a dark sky. Photographed in Finland | |
Licence : | Droits gérés |
Crédit: | Science Photo Library / PEKKA PARVIAINEN |
Taille de l’image : | 5250 px × 3612 px |
Model Release : | Non requis |
Property Release : | Non requis |
Restrictions : | - |