Neith is a hypothetical

natural satellite A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are often colloquially referred to as ''moons'' ...

Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never f ...

reportedly sighted by

Giovanni Cassini Giovanni Domenico Cassini, also known as Jean-Dominique Cassini (8 June 1625 – 14 September 1712) was an Italian (naturalised French) mathematician, astronomer and engineer. Cassini was born in Perinaldo, near Imperia, at that time in the ...

in 1672 and by several other astronomers in following years. The first supposed sighting of this moon was in 1650. It was 'observed' up to 30 times by astronomers until 1770, when there were no new sightings and it was not found during the transit of Venus in 1761 and 1769.

Discovery

In 1672, Giovanni Cassini found a small object close to Venus. He did not take great note of his observation, but when he saw it again in 1686, he made a formal announcement of a possible moon of Venus. The object was seen by many other

astronomers An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either obse ...

over a large period of time: by James Short in 1740, by Andreas Mayer in 1759, by

Joseph Louis Lagrange Joseph-Louis Lagrange (born Giuseppe Luigi Lagrangiatransit Transit may refer to: Arts and entertainment Film * ''Transit'' (1979 film), a 1979 Israeli film * ''Transit'' (2005 film), a film produced by MTV and Staying-Alive about four people in countries in the world * ''Transit'' (2006 film), a 2006 ...

across the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

, eight observations in 1764, and by

Christian Horrebow Christian Pedersen Horrebow (15 April 1718 – 15 September 1776) was a Danish astronomer of the 18th century. He was a son of Peder Horrebow, whom he succeeded as director of the observatory associated with the University of Copenhagen. He was h ...

in 1768.

Summary of sightings

Observations

Many astronomers failed to find any moon during their observations of Venus, including

William Herschel Frederick William Herschel (; german: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline ...

in 1768. Cassini originally observed Neith to be one-fourth the diameter of Venus. In 1761, Lagrange announced that Neith's

orbital plane The orbital plane of a revolving body is the geometric plane in which its orbit lies. Three non-collinear points in space suffice to determine an orbital plane. A common example would be the positions of the centers of a massive body (host) an ...

was perpendicular 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 ...

. That same year, however, mathematician

Jean le Rond d'Alembert Jean-Baptiste le Rond d'Alembert (; ; 16 November 1717 – 29 October 1783) was a French mathematician, mechanician, physicist, philosopher, and music theorist. Until 1759 he was, together with Denis Diderot, a co-editor of the '' Encyclopéd ...

wrote to

Voltaire François-Marie Arouet (; 21 November 169430 May 1778) was a French Enlightenment writer, historian, and philosopher. Known by his ''nom de plume'' M. de Voltaire (; also ; ), he was famous for his wit, and his criticism of Christianity—es ...

that Neith had "declined to follow his mistress during her passage over the sun", questioning whether Venus truly had a moon. In 1766, the director of the

Vienna Observatory The Vienna Observatory (german: Universitätssternwarte Wien) is an astronomical observatory in Vienna, Austria. It is part of the University of Vienna. The first observatory was built in 1753–1754 on the roof of one of the university buildings ...

speculated that the observations of the moon were

optical illusions Within visual perception, an optical illusion (also called a visual illusion) is an illusion caused by the visual system and characterized by a visual percept that arguably appears to differ from reality. Illusions come in a wide variety; the ...

. He said: "the bright image of Venus was reflected in the eye and back into the

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observ ...

, creating a smaller secondary image." In 1777, J.H. Lambert estimated its orbital period as eleven days and three hours. In 1884,

Jean-Charles Houzeau Jean-Charles Houzeau de Lehaie (October 7, 1820 – July 12, 1888) was a Belgian astronomer and journalist. A French speaker, he moved to New Orleans after getting in trouble for his politics in Belgium. In the U.S. he continued his journalistic ...

, the former director of the Royal Observatory of Brussels suggested that the "moon" was actually a planet which orbited the Sun every 283 days. Such a planet would be in conjunction with Venus every 1080 days, which fit with the recorded observations. Houzeau was also the first to give the object the name Neith, after an Egyptian goddess. The Belgian Academy of Sciences published a paper in 1887 which studied each reported sighting of Neith. Ultimately, they determined that most of the sightings could be explained by stars which had been in the vicinity of Venus, including Chi Orionis, M Tauri, 71 Orionis, Nu Geminorum and

Theta Librae θ Librae, Latinised as Theta Librae, is a single star in the southern zodiac constellation of Libra, near the constellation border with Scorpius. It is visible to the naked eye as a faint, orange-hued star with an apparent visual mag ...

References

External links

Neith, the Moon of Venus
{{DEFAULTSORT:Neith (Hypothetical Moon) Hypothetical bodies of the Solar System Hypothetical moons Venus Planetary satellite systems

Discovery

Summary of sightings

Observations

See also

References

External links