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

satellite A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...

, which he promptly named

Themis In Greek mythology and religion, Themis (; ) is the goddess and personification of justice, divine order, law, and custom. She is one of the twelve Titan children of Gaia and Uranus, and the second wife of Zeus. She is associated with oracles a ...

after the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

goddess of divine law and order. The thirteen photographic plates on which it supposedly appeared spanned a period between April 17 and July 8, 1904. No other astronomer 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 Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

), 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 In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the longe ...

() slightly less than that of Hyperion. The period was supposedly 20.85 days, with prograde motion. Pickering estimated Themis's diameter at 38 miles (61 km), based on his assumptions that Themis's

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 ...

was the same as Titan's, and that Titan's diameter was about 2300 miles. Today, Titan's diameter is known to be closer to 3200 miles. The same assumptions led him to a diameter of 42 miles (68 km) for Phoebe, far less than Phoebe's true diameter of roughly 132 miles (213 km). 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 for ...

. It does not exist, though the name was used much later for the large

comet A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...

and

centaur A centaur ( ; ; ), occasionally hippocentaur, also called Ixionidae (), is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse that was said to live in the mountains of Thessaly. In one version o ...

2060 Chiron 2060 Chiron is a ringed 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— ...

. 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 1801 ...

of the

French Academy of Sciences The French Academy of Sciences (, ) is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French Scientific method, scientific research. It was at the forefron ...

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 In ancient Roman religion and myth, Janus ( ; ) is the god of beginnings, gates, transitions, time, duality, doorways, passages, frames, and endings. He is usually depicted as having two faces. The month of January is named for Janus (''Ianu ...

, which was discovered in 1966 and confirmed in 1980.

In fiction

Philip Latham (pen-name of

Robert S. Richardson Robert Shirley Richardson (April 22, 1902 – November 12, 1981) was an American astronomer, born in Kokomo, Indiana. He also published science fiction using the pseudonym A pseudonym (; ) or alias () is a fictitious name that a person assumes ...

), in his 1953 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 th ...

'', has Themis collide with Titan, "getting rid of the little nuisance once and for all", according to the introduction. John Varley's 1979

science fiction Science fiction (often shortened to sci-fi or abbreviated SF) is a genre of speculative fiction that deals with imaginative and futuristic concepts. These concepts may include information technology and robotics, biological manipulations, space ...

novel ''

Titan Titan most often refers to: * Titan (moon), the largest moon of Saturn * Titans, a race of deities in Greek mythology Titan or Titans may also refer to: Arts and entertainment Fictional entities Fictional locations * Titan in fiction, fictiona ...

'' is set aboard an expedition to Saturn. During the novel, 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 1979-1981

Schrödinger's Cat trilogy The ''Schrödinger's Cat Trilogy'' is a trilogy of novels by American writer Robert Anton Wilson consisting of ''Schrödinger's Cat: The Universe Next Door'' (1979), ''Schrödinger's Cat II: The Trick Top Hat'' (1980), and ''Schrödinger's Cat II ...

of novels makes frequent reference to Pickering's Moon as a satellite that revolves the "wrong way" (i. e.

retrograde Retrograde may refer to: Film and television * Retrograde (2004 film), ''Retrograde'' (2004 film), a film by Christopher Kulikowski * Retrograde (2022 American film), ''Retrograde'' (2022 American film), a documentary film by Matthew Heineman * ...

) around its primary. Likewise, the ''

Principia Discordia The ''Principia Discordia'' is the first published Discordianism, Discordian religious text. It was written by Greg Hill (Malaclypse the Younger) with Kerry Wendell Thornley (Lord Omar Khayyam Ravenhurst) and others. The first edition was printed ...

'' asks in the novel: "Why does Pickering's Moon go about in reverse orbit?"

Nelson S. Bond Nelson Slade Bond (November 23, 1908 – November 4, 2006) was an American writer. His works included books, magazine articles, and scripts used in radio, for television and on the stage. The 1998 recipient of the Nebula Author Emeritus award ...

, 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)

In fiction

References

See also