For a few months now Jupiter has been a dazzling evening object, visible just after sunset and dominating the night sky among the stars of the bright zodiacal constellation of Taurus. The culmination of this year's visibility occurs on December 3rd, when the King of the planets reaches opposition and is at its most brilliant.
Location and appearance
At opposition this year, Jupiter shines at magnitude -2.8 and has an apparent diameter of 48 arc seconds. The gas giant, currently moving retrograde, is located 5 degrees north of orange/red first magnitude star Aldebaran and the adjacent large beautiful binocular open cluster, the Hyades. The Pleiades (M45), the most famous open cluster in the sky is positioned about 12 degrees to the west and a little north of Jupiter.
This year's Jupiter opposition is only slightly inferior to last years in terms of apparent brightness and diameter. The 2011 opposition occurred on October 29th when Jupiter was closer to the Earth; hence the planet appeared fractionally brighter and larger in the sky. At opposition last year, Jupiter’s apparent magnitude was -2.9 with an apparent diameter close to 50 arc seconds.
Compared to last year, the differences are minimal and the planet is still excellently placed in 2012; Jupiter is only 0.1 magnitudes fainter and less than 2 arc seconds smaller in apparent diameter. For northern hemisphere observers the difference is more than offset by the planets more favourable declination; 10 degrees further north than last year. Southern hemisphere observers don't have it quite so good, since Jupiter does not rise quite so high in the sky. But as always for all observers, regardless of location, Jupiter is a fantastic object to view. This is especially true around the time of opposition, with this year again being no exception.
When viewed through popular 7x50 and 10x50 binoculars the disk of Jupiter is apparent, appearing off white or creamy in colour but without surface detail. The four large Galilean moons (Io, Europa, Ganymede and Callisto) are clearly visible. The moons continuously change position as they orbit Jupiter and sometimes all four are visible, but on other occasions some or all of the satellites will be temporarily obstructed and hidden as they pass behind or in front of Jupiter's disk. The moons of Jupiter are theoretically all bright enough to be seen with the naked eye, although their close proximity to the searchlight like beam of Jupiter makes this task almost impossible. However, a few very keen eyed observers have claimed to spot the moons without optical aid. At opposition this year, Io shines at magnitude 4.9, Europa magnitude 5.2, Ganymede magnitude 4.5 and Callisto at magnitude 5.6.
An excellent tool to predict the positions of the Galilean moons can be found at Sky and Telescope magazine: Sky and Telescope - Galilean moons
Through a telescope a wealth of detail is visible on the planets disk. Even a small 60mm (2.4-inch) telescope at medium to high magnification will begin to show some surface detail including the great Northern and Southern Equatorial belts. Keen eyed observers under good seeing conditions may even be able to notice the shadow transits of the Galilean moons. A larger 100mm (4-inch) telescope will reveal more details in the belts including bright and dark spots. Also visible is the most famous storm of all on Jupiter "The Great Red Spot". With a 200mm (8-inch) telescope or larger, Jupiter is a spectacular sight with the brighter features well defined along with all sorts of intriguing and subtle details.
Generally, if the seeing conditions are good it is possible to push a telescope close to the magnitude limit when observing Jupiter. The accepted values are 50x for every 25mm (1-inch) of aperture. So up to 200x for a 100mm (4-inch) telescope and 400x for a 200mm (8-inch) telescope.
Jupiter and its moons are appealing and rewarding objects when viewed through all types of optical instrument. At opposition on December 3, 2012 the giant planet is at its sublime best. Take the opportunity to observe Jupiter and it's moons as they are always wonderful, fascinating and you never know quite what to expect.
Jupiter Opposition 2012 Data Table
|Opposition Date||December 3, 2012|
|Distance from Earth (AU)||4.0688|
|Distance from Earth (Million Kilometres)||608.684|
|Distance from Earth (Million Miles)||378.219|
|RA (J2000)||04h 38m 39s|
|DEC (J2000)||21d 19m 14s|
|Apparent Diameter (arcsecs)||48.5|