Dia

Dia, also known as Jupiter LIII, is the second-outermost known prograde irregular satellite of Jupiter. Provisionally known as S/2000 J 11, it received its name on 7 March 2015. It is named after Dia, daughter of Deioneus (or Eioneus), wife of Ixion. According to Homer, she was seduced by Zeus in stallion form; Pirithous was the issue.

The satellite is the only known small body in the Himalia group.

Dia is believed to be about 4 kilometres in diameter. It orbits Jupiter at an average distance of 12 million km in 274 days, at an inclination of 28° (to Jupiter's equator), and with an eccentricity of 0.21.

Discovery
Dia was discovered by a team of astronomers from the University of Hawaii led by Scott S. Sheppard in 2000 with an observation arc of 26 days.

Initial observations were not followed up, and Dia was not observed for more than a decade after 2000. This apparent disappearance led some astronomers to consider the moon lost. One theory was that it had crashed into Himalia, creating a faint ring around Jupiter. However, it was finally recovered in observations made in 2010 and 2011.