The Moon that Wasn't: The Saga of Venus' Spurious SatelliteThe planet Venus is the closest neighbour to the Earth and in several respects similar to our globe. It revolves around the Sun at an average distance of 0. 72 astronomical units, in an elliptical orbit of eccentricity 0. 007. The corresponding 3 numbers for the Earth are 1 and 0. 017. The mean density of Venus is 5. 2 g/cm , 3 that of the Earth 5. 5 g/cm . Venus’ acceleration of gravity at its equator is 8. 9 2 2 m/s , compared with 9. 8 m/s at the Earth. The escape velocity is 10. 4 km/s, while the corresponding ?gure of the Earth is 11. 2 km/s. Although the mass of Venus is somewhat smaller than that of the Earth – the ratio is M /M =0. 815 V E – the diameters of the two planets are almost the same. In other words, Venus is indeed a sister planet of the Earth. In earlier times, when almost nothing was known about the physical con- tions of Venus, the similarity appeared even stronger than today. Not only was Venus’ period of rotation thought to be close to that of the Earth, it was also p- sible (and indeed common) to imagine intelligent life on Venus. |
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Académie des Sciences amateur astronomer appeared asteroids Astronomische atmosphere Baudouin believed Berlin Bianchini bolides Boscovich Cassini celestial Christian Horrebow comet Copenhagen discovered discovery claim Earth edition Encyclopédie existence explain Fontana French astronomer Hell Herschel Histoire History of Astronomy Horrebow Houzeau Huygens hypothesis included Jean Johann Journal Jupiter known l'Académie Royale Lalande Lambert Lassell later London Mairan mass of Venus mathematics Maximilian Hell Mémoires mentioned Montaigne Montbarron Monthly Notices moon of Venus natural object observation claims observations of Venus Observatory optical illusions orbit Paris Petit Philosophical Transactions Pickering planetary published referred reported Roedkiær Royal Astronomical Society Royale des Sciences satellite de Vénus satellite of Venus satellites of Mars satellites of Uranus Saturn Schorr Schröter scientific second moon seen Sheehan solar system star Stroobant suggested sunspots telescope theory Thirion thought Titius-Bode law transit of Venus Uranus Veneris Venus moon Venus satellite Venus transit William William Herschel William Lassell wrote