July 06 – Discovery of Jupiter’s moon, Lysithea (1938).

Lysithea, discovered today in 1938 by Seth B Nicholson at Mount Wilson, is the second smallest of the Himalia group of Jupiter‘s moons (the others being Himalia, Leda and Elara).  This small group of moons, all about 11 million km from Jupiter, are similar in appearance and behaviour, and are therefore thought to have a common origin, possibly a C- or D-class asteroid.

Lysithea is named after a daughter of Oceanus, and was one of Zeus’ many conquests.  And apart from these scanty facts there is just about nothing else I can find out about her.  Newly discovered Jovian moons are all now named after lovers of Jupiter (Zeus) and as a rule end in an ‘a’ or an ‘o’ if they are prograde (orbit in the same direction as the planet) or an ‘e’ if they are retrograde (orbit in the opposite direction to the planet).

Being a mere 18 km across, and 778 million km away, there are no great photographs of Lysithea available.  I was tempted to draw a black square and put a single spot of white on it, but I resisted.