Themisto (moon)

Themisto (Template:IPAc-en), also known as Template:Nowrap, is a small prograde irregular satellite of Jupiter. It was discovered in 1975, subsequently lost, and rediscovered in 2000.

Discovery and naming

File:Themisto-Holman-CFHT.gif

Themisto observed by the Canada–France–Hawaii Telescope on 6Template:NbspAugust 2000, several months before its rediscovery in November 2000

Themisto was first discovered by Charles T. Kowal and Elizabeth Roemer on 30Template:NbspSeptember 1975, reported on 3Template:NbspOctober 1975,<ref name="IAUC2845">Template:Cite web</ref> and designated Template:Nowrap. However, not enough observations were made to establish an orbit and it was subsequently lost.

Then, on 21Template:NbspNovember 2000, a seemingly new satellite was discovered by Scott S. Sheppard, David C. Jewitt, Yanga R. Fernández and Eugene A. Magnier and was designated Template:Nowrap. It was soon confirmed from computing the past trajectory of the satellite that this was the same as the one observed in 1975.<ref name="IAUC7525">Template:Cite web</ref> This observation was immediately correlated with an earlier observation on 6Template:NbspAugust 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).<ref name="MPEC-2000-Y16">Template:Cite web</ref>

In October 2002, it was officially named after Themisto,<ref>Template:Cite web</ref> daughter of the river god Inachus and lover of Zeus (Jupiter) in Greek mythology.

Characteristics

File:TheIrregulars JUPITER GROUPS.svg

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 Template:Cvt in diameter (assuming an albedo of 0.04).<ref name="SheppardMoons"/> While its true albedo could not be measured by NEOWISE due to poor timing of observations,<ref name="Grav2015">Template:Cite journal</ref> it is known to have color index B−V=0.83, V−R=0.46, and V−I=0.94.<ref name="Grav2003">Template:Cite journal</ref>

External links

• David Jewitt's pages
• Jupiter's Known Satellites Template:Webarchive (by Scott S. Sheppard)
• Template:Cite web
• Template:Cite web