Noctilucent clouds. These bright displays are seen in the middle of the night in summer at high latitudes. Their composition 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 : | 5081 px × 3543 px |
Model Release : | Non requis |
Property Release : | Non requis |
Restrictions : | - |