Themisto observed by the Canada-France-Hawaii Telescope on 6 August 2000, several months before its rediscovery in November 2000
Themisto was first discovered by Charles T. Kowal and Elizabeth Roemer on 30 September 1975, reported on 3 October 1975,[1] and designated S/1975 J 1. However, not enough observations were made to establish an orbit and it was subsequently lost.
Diagram illustrating Themisto's orbit (top left) among those of the other irregular satellites of Jupiter. The satellites above the horizontal axis are prograde, the satellites beneath it are retrograde. The yellow segments extend from the pericentre to the apocentre, showing the orbital eccentricity.
Themisto's orbit is unusual: unlike most of Jupiter's moons, which orbit in distinct groups, Themisto orbits alone. The moon is located midway between the Galilean moons and the first group of prograde irregular moons, the Himalia group.
Themisto is about 9 km (5.6 mi) in diameter (assuming an albedo of 0.04).[6] While its true albedo could not be measured by NEOWISE due to poor timing of observations,[10] it is known to have color index B−V=0.83, V−R=0.46, and V−I=0.94.[11]
^ abBrian G. Marsden (25 November 2000). "IAUC 7525: S/1975 J 1 = S/2000 J 1". International Astronomical Union Central Bureau for Astronomical Telegrams.
^Cf. 'Themista' in Noah Webster (1884). A Practical Dictionary of the English Language.
^'Themis[t]oan' in James Hall (2015). Moons of the Solar System. p. 82.
^ ab"M.P.C. 110499"(PDF). Minor Planet Circular. Minor Planet Center. 29 May 2018.
^ abcSheppard, Scott. "Scott S. Sheppard - Jupiter Moons". Department of Terrestrial Magnetism. Carnegie Institution for Science. Retrieved 26 November 2020.
