Themisto (), also known as , is a small prograde irregular satellite of

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

. It was discovered in 1975, subsequently lost, and rediscovered in 2000.

Discovery and naming

Themisto was first discovered by Charles T. Kowal and Elizabeth Roemer on 30September 1975, reported on 3October 1975, and designated '. However, not enough observations were made to establish an orbit and it was subsequently lost. Then, on 21November 2000, a seemingly new satellite was discovered by Scott S. Sheppard, David C. Jewitt, Yanga R. Fernández and Eugene A. Magnier and was designated '. It was soon confirmed from computing the past trajectory of the satellite that this was the same as the one observed in 1975. This observation was immediately correlated with an earlier observation on 6August 2000 by the team of Brett J. Gladman, John J. Kavelaars, Jean-Marc Petit, Hans Scholl, Matthew J. Holman, Brian G. Marsden, Philip D. Nicholson and Joseph A. Burns, which was reported to the Minor Planet Center but not published as an IAU Circular (IAUC). In October 2002, it was officially named after Themisto, daughter of the river god Inachus and lover of

Zeus Zeus (, ) is the chief deity of the List of Greek deities, Greek pantheon. He is a sky father, sky and thunder god in ancient Greek religion and Greek mythology, mythology, who rules as king of the gods on Mount Olympus. Zeus is the child ...

(Jupiter) in

Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...

Characteristics

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 The Galilean moons (), or Galilean satellites, are the four largest moons of Jupiter. They are, in descending-size order, Ganymede (moon), Ganymede, Callisto (moon), Callisto, Io (moon), Io, and Europa (moon), Europa. They are the most apparent m ...

and the first group of prograde irregular moons, the Himalia group. Themisto is about in diameter (assuming an

albedo Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...

of 0.04). While its true albedo could not be measured by NEOWISE due to poor timing of observations, it is known to have color index B−V=0.83, V−R=0.46, and V−I=0.94.

References

External links

David Jewitt's pages

(by Scott S. Sheppard) * * {{DEFAULTSORT:Themisto (Moon) Moons of Jupiter Irregular satellites Discoveries by Charles T. Kowal Discoveries by Elizabeth P. Roemer Discoveries by Scott S. Sheppard Discoveries by David C. Jewitt Discoveries by Yanga R. Fernandez Discoveries by Eugene A. Magnier 19750930 20001121 Moons with a prograde orbit