Neith (hypothetical moon)
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Neith is a hypothetical natural satellite of Venus reportedly sighted by Giovanni Cassini in 1672 and by several other astronomers in following years. 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.[1][2]
Discovery
[edit]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.[3] The object was seen by many other astronomers over a large period of time: by James Short in 1740,[4] by Andreas Mayer in 1759,[4] by Louis Lagrange in 1761,[5] another eighteen observations in 1761, including one in which a small spot was seen following Venus while the planet was in a transit across the Sun, eight observations in 1764, and by Christian Horrebow in 1768.[6]
Summary of sightings
[edit]| Year | City | Person | Number of sightings |
|---|---|---|---|
| 1645 | Naples | Francesco Fontana | 3[4] |
| 1646 | Naples | Francesco Fontana | 1[4] |
| 1672 | Paris | Giovanni Domenico Cassini | 1[4] |
| 1686 | Paris | Giovanni Domenico Cassini | 1[4] |
| 1740 | London | James Short | 1[4] |
| 1759 | Greifswald | Andreas Mayer | 1[4] |
| 1761 | Marseilles | Joseph Lagrange | 3 |
| 1761 | Limoges | Jacques Montaingne | 4 |
| 1761 | St. Neots | unknown | 1 |
| 1761 | Greifswald | Friedrich Artzt | 1 |
| 1761 | Krefeld | Abraham Scheuten | 2 |
| 1761 | Copenhagen | Peter Roedkiær | 8 |
| 1764 | Copenhagen | Peter Roedkiær | 2 |
| 1764 | Copenhagen | Christian Horrebow and others | 3 |
| 1764 | Auxerre | Marian | 3 |
| 1768 | Copenhagen | Christian Horrebow | 1 |
Observations
[edit]Many astronomers failed to find any moon during their observations of Venus, including William Herschel in 1768[citation needed]. Cassini originally observed Neith to be one-fourth the diameter of Venus. In 1761, Lagrange announced that Neith's orbital plane was perpendicular to the ecliptic.[5] That same year, however, mathematician Jean le Rond d'Alembert wrote to Voltaire that Neith had "declined to follow his mistress during her passage over the sun", questioning whether Venus truly had a moon.[7] In 1766, the director of the Vienna Observatory speculated that the observations of the moon were optical illusions. He said: "the bright image of Venus was reflected in the eye and back into the telescope, creating a smaller secondary image."[citation needed] In 1777, J.H. Lambert estimated its orbital period as eleven days and three hours.[citation needed]
In 1884, Jean-Charles Houzeau, 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.[citation needed]
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.[citation needed]
See also
[edit]- List of hypothetical astronomical objects
- 524522 Zoozve, a quasi-satellite of Venus
- 2013 ND15, a temporary trojan of Venus
References
[edit]- ^ Helge Kragh (2008). The Moon that Was not: The Saga of Venus' Spurious Satellite. Birkhäuser. ISBN 978-3-7643-8908-6.
- ^ Pedersen, Kurt Møller; Kragh, Helge (19 Apr 2023). "THE PHANTOM MOON OF VENUS, 1645-1768". Journal of Astronomical History and Heritage. 11 (3): 227–234. doi:10.3724/SP.J.1440-2807.2008.03.07.
- ^ Pedersen 2023, p. 227.
- ^ a b c d e f g h Pedersen 2023, p. 228.
- ^ a b Pedersen 2023, p. 229.
- ^ Pedersen 2023, p. 232.
- ^ Stevenson, David (2014). "Making the Moon" (PDF). Physics Today: 37. Retrieved 1 May 2022.
