Optical photograph of Halley's comet taken on 9 April,1986,the night before the comet's closest approach to Earth. Named after Edmund Halley (1656-1742),who first recognised its periodicity,the comet has been recorded every 76 years since 240 BC. It consists of a potato- shaped nucleus of ice & dust. Its tail is formed as the comet is heated when it approaches the Sun. Dust & gas are released and swept into a tail both by radiation pressure and by the solar wind. The photo is a one hour exposure which tracked the moving comet,and shows background star trails | |
Licence : | Droits gérés |
Crédit: | Science Photo Library / NOAO |
Taille de l’image : | 5197 px × 3539 px |
Model Release : | Non requis |
Property Release : | Non requis |
Restrictions : |
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