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Mercury, the smallest and innermost planet, has no moons, or at least none that can be detected to a diameter of 1.6 km (1.0 mi). [2] For a very short time in 1974, Mercury was thought to have a moon. Venus also has no moons, [3] though reports of a moon around Venus have circulated since the 17th century.
The timeline of discovery of Solar System planets and their natural satellites charts the progress of the discovery of new bodies over history. Each object is listed in chronological order of its discovery (multiple dates occur when the moments of imaging, observation, and publication differ), identified through its various designations (including temporary and permanent schemes), and the ...
The Persian polymath Avicenna claimed to have observed Venus as a spot on the Sun. There was a transit on 24 May 1032, but Avicenna did not give the date of his observation, and modern scholars have questioned whether he could have observed the transit from his location; he may have mistaken a sunspot for Venus.
Consequently, Venus transits only occur when an inferior conjunction takes place during some days of June or December, when the orbits of Venus and Earth cross a straight line with the Sun. [189] This results in Venus transiting above Earth in a sequence currently of 8 years, 105.5 years, 8 years and 121.5 years, forming cycles of 243 years.
There have been 46 space missions to the planet Venus (including gravity-assist flybys). Missions to Venus constitute part of the exploration of Venus. The Soviet Union, followed by the United States, have soft landed probes on the surface. Venera 7 was the first lander overall and first for the Soviet Union, touching down on 15 December 1970.
"On the fifth night in the month of May appeared the moon shining bright in the evening, and afterwards by little and little its light diminished."
In the Dresden Codex, the Maya included an almanac showing Venus's full cycle, in five sets of 584 days each (approximately eight years), after which the patterns repeated (since Venus has a synodic period of 583.92 days). [12] The Maya were aware of this synodic period, and could compute it to within a hundredth part of a day. [11]
And as you might have guessed, full moons are kind of special. They only come once a month—or every 29.5 days, if you want to be exact—so there are 12 or 13 every year.