Jupiter and Moon Conjunction

Photograph taken from our garden last night
 using Toot's  hand-held Sony Compact Camera

You might have noticed that the Moon had a bright companion last night.  The planet Jupiter appeared to be sitting alongside the waning gibbous Moon.  It was however, a line of sight illusion as Jupiter varies  between 629 and 928 million  km in distance from Earth and the Moon only varies between 363 and 407 thousand  km.  Jupiter is also much much larger than the Moon, it's diameter being approximately 45 times bigger.  Jupiter only  appears as a star-like point of light because it is so far away, viewed under 25x or more magnification in a small telescope it presents clearly as a disc.  


Jupiter is a gas giant, 90% hydrogen and  9% helium.  It has the fastest rate of spin of all the planets and completes a full rotation every 9.9 hours.  The resulting centrifugal force (or lack of centripetal acceleration) causes the shape of Jupiter to deform from the pure sphere dictated by gravity.  Jupiter's diameter measured around its equator is therefore significantly greater than when measured over its poles. Jupiter's shape is described as oblate.  In a small telescope this deformation is quite obvious to even an untrained eye.
Jupiter has its own retinue of  some 63 moons, four of which. the Galilean Moons, can be seen through 10x50 mm binoculars. The number of these larger moons visible and their positions vary according to their position in orbit around Jupiter and whether they are or not in eclipse.