Jupiter is much the largest and most massive planet in the Solar System; its mass is greater than those of all the other planets combined. It has been suggested that it may have been responsible for preventing approaching comets invading the inner Solar System, and thereby protecting the Earth from bombardment. Data are given in Table 9.1. Figure 9.1 is a surface map.

MOVEMENTS

Jupiter is well placed for observation for several months in every year. The opposition brightness has a range of about 0.5 magnitude. Generally speaking it ‘moves’ about one constellation per year; thus the opposition of 2003 was in Cancer, that of 2004 in Leo, 2005 in Virgo, and so on. Opposition dates for 2008–2020 are given in Table 9.2. Some years pass without an opposition; thus that of 3 December 2012 is followed by the next on 8 January 2014, missing out 2013.

Jupiter passes perihelion on 17 March 2011 (4.95 a.u.), and aphelion (5.46 a.u.) on 17 February 2017.

Generally, Jupiter is the brightest of the planets apart from Venus; its only other rival is Mars at perihelic opposition.