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Phenomena related to eclipses
About 13 times a century for Mercury and in pairs eight years apart separated by more than a century for Venus , we see these planets transit the Sun ’ s disk . The silhouette of the planet passes across the disk of the Sun , taking a few hours to make the full crossing . Mercury ’ s silhouette is tiny , invisible without a telescope . The silhouette of Venus is large enough that with a safe solar filter you can see it without a telescope ; with a telescope Venus is a small but distinct disk . Asteroids and comets can also transit . Halley ’ s Comet was predicted to transit the Sun in 1910 but the passage was not visible in telescopes . This told astronomers that the solid nucleus of the comet was small . Earth satellites also transit the Sun ( and Moon ) on occasion . The pass takes about 1 second . The distinctive shape of the International Space Station can be seen and imaged . Sometimes spacecraft see the Moon crossing the Sun ’ s disk . It ’ s sometimes not obvious whether to call the event an annular eclipse or a transit . We call an event when a larger body passes in front of a smaller body in the sky an occultation . If we were consistent using definitions of astronomical phenomena , a total solar eclipse would be called a total occultation of the Sun . Only events during which we see the shadow of one object fall projected on another object would be called an eclipse ( like an eclipse , total or partial , of the Moon when it passes through Earth ’ s shadow ). But in common usage , an occultation refers to ( usually ) night time events such as the Moon passing in front of ( occulting ) a star or asteroid or planet . There are also occasions when an asteroid or planet occults a star . See the discussion of Jupiter in Sidebar Two for more information .
COURTESY OF Steve Edberg
COURTESY OF Steve Edberg Venus is much larger than the sunspots visible on the Sun ’ s disk to its right .
COURTESY OF NASA / Bill Ingalls Above , this composite image made from five frames shows the International Space Station , with a crew of nine onboard , in silhouette as it transits the Sun at roughly five miles per second on Sept . 6 , 2015 . Left , in this view , the Moon is partially occulting Saturn . At most locations for viewing this event , Saturn eventually disappeared completely behind the Moon and reappeared an hour or less later . From this site , the Moon never completely covered Saturn and spent about five minutes sliding by , partially covering the planet . Notice that Saturn is covered by a narrow piece of the night side of the Moon , not by the mountains illuminated by Sun in the foreground .
Sky ’ s Up 17