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A transit of Venus takes place when Venus passes directly between the Sun and the Earth (or any other superior planet), becoming visible against (and hence obscuring a small portion of) the solar disk. During a transit, Venus is visible as a small black circle moving across the face of the Sun. Transits of Venus reoccur periodically.
[1] [2] The low eccentricity and comparatively small size of its orbit give Venus the least range in distance between perihelion and aphelion of the planets: 1.46 million km. The planet orbits the Sun once every 225 days [3] and travels 4.54 au (679,000,000 km; 422,000,000 mi) in doing so, [4] giving an average orbital speed of 35 km/s (78,000 ...
Venus has a diameter of 12,103.6 km (7,520.8 mi)—only 638.4 km (396.7 mi) less than Earth's—and its mass is 81.5% of Earth's, making it the third-smallest planet in the Solar System. Conditions on the Venusian surface differ radically from those on Earth because its dense atmosphere is 96.5% carbon dioxide, with most of the remaining 3.5% ...
The astronomical unit is typically used for stellar system scale distances, such as the size of a protostellar disk or the heliocentric distance of an asteroid, whereas other units are used for other distances in astronomy. The astronomical unit is too small to be convenient for interstellar distances, where the parsec and light-year are
In 1672 Jean Richer and Giovanni Domenico Cassini measure the astronomical unit (AU), the mean distance Earth-Sun, to be about 138,370,000 km, [83] (later refined by others up to the current value of 149,597,870 km). This gave for first time ever a well estimated size of the then known Solar System (that is, up to Saturn), following the scale ...
A picture of the 2012 transit of Venus by the Solar Dynamics Observatory, from 36,000 km (22,000 mi) above the Earth. A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and Earth. It is one of the rarest predictable astronomical phenomena and happens in pairs eight years apart that are separated ...
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The observation by Mikhail Lomonosov of the transit of 1761 provided the first evidence that Venus had an atmosphere, and the 19th-century observations of parallax during Venus transits allowed the distance between the Earth and Sun to be accurately calculated for the first time. Transits can only occur either in early June or early December ...