On April 28, 1905, William H. Pickering, who had seven years earlier discovered Phoebe, announced the discovery of a tenth

satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioi ...

of Saturn, which he promptly named Themis after the goddess of divine law and order from Greek mythology. The photographic plates on which it supposedly appeared, thirteen in all, spanned a period between April 17 and July 8, 1904. However, no other astronomer has ever confirmed Pickering's claim. Pickering attempted to compute an orbit, which showed a fairly high

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

(39.1° to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic agains ...

), fairly large

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

(0.23) and a semi-major axis () slightly less than that of Hyperion. The period was supposedly 20.85 days, with prograde motion. Pickering estimated the diameter at , but since he also gave as the diameter of Phoebe, he was clearly overestimating the

albedo Albedo (; ) is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that refl ...

; using the modern figure for Phoebe gives Themis a diameter of . Oddly, in April 1861,

Hermann Goldschmidt Hermann Mayer Salomon Goldschmidt (June 17, 1802 – August 30 or September 10 1866) was a German-French astronomer and painter who spent much of his life in France. He started out as a painter, but after attending a lecture by the famous Fren ...

had also believed that he had discovered a new satellite of Saturn between Titan and Hyperion, which he called

Chiron In Greek mythology, Chiron ( ; also Cheiron or Kheiron; ) was held to be the superlative centaur amongst his brethren since he was called the "wisest and justest of all the centaurs". Biography Chiron was notable throughout Greek mythology ...

. Chiron also does not exist (however, the name was used much later for the

comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ...

/ asteroid

2060 Chiron 2060 Chiron is a small Solar System body in the outer Solar System, orbiting the Sun between Saturn and Uranus. Discovered in 1977 by Charles Kowal, it was the first-identified member of a new class of objects now known as centaurs—bodies o ...

). Pickering was awarded the

Lalande Prize The Lalande Prize (French: ''Prix Lalande'' also known as Lalande Medal) was an award for scientific advances in astronomy, given from 1802 until 1970 by the French Academy of Sciences. The prize was endowed by astronomer Jérôme Lalande in 180 ...

of the French Academy of Sciences in 1906 for his "discovery of the ninth and tenth satellites of Saturn". The actual tenth satellite of Saturn (in order of discovery) was Janus, which was discovered in 1966 and confirmed in 1980. There is also an asteroid named

24 Themis Themis ( minor planet designation: 24 Themis) is one of the largest asteroids in the asteroid belt. It is also the largest member of the Themistian family. It was discovered by Annibale de Gasparis on 5 April 1853. It is named after Themis, th ...

Themis in fiction

* Philip Latham (pen-name of Robert S. Richardson), in his novel ''

Missing Men of Saturn ''Missing Men of Saturn'' is a juvenile science fiction novel, published first in 1953, by astronomer and author Robert S. Richardson (as Philip Latham) with cover illustration by Alex Schomburg. The story concerns Dale Sutton's mission to the ...

'', has Themis collide with Titan, "getting rid of the little nuisance once and for all", according to the introduction. * John Varley's

science fiction Science fiction (sometimes shortened to Sci-Fi or SF) is a genre of speculative fiction which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel uni ...

novel '' Titan'' is set aboard an expedition to Saturn. As they approach the planet and prepare to enter orbit, the astronomer onboard discovers a new moon. At first she believes she has recovered Pickering's lost moon, so she names it Themis. * Robert Anton Wilson's

Schrödinger's Cat trilogy The ''Schrödinger's Cat Trilogy'' is a trilogy of novels by American writer Robert Anton Wilson consisting of ''The Universe Next Door'' (1979), ''The Trick Top Hat'' (1980), and ''The Homing Pigeons'' (1981), each illustrating a different inte ...

of novels makes frequent reference to Pickering's Moon as a satellite that revolves the "wrong way" (i. e. retrograde) around its primary. * Nelson S. Bond, in his 1943 science-fiction story " The Ordeal of Lancelot Biggs," explains that Themis periodically disappears when it is occulted by its own moon, an invisible body with "the peculiar property of being able to warp light waves around itself."

References

Deguy: Le cosmos revue encyclopedique hebdomadaire des progres des sciences et de leurs applications aux arts et a l'industrie, p.421 (1861)

Annals of Harvard College Observatory, vol. 53, no. 9, pp. 173-185 (1905)

Harvard College Observatory Bulletin No. 189, p.1 (April 1905)

Themis in fiction

References

See also