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The planetary hours are an ancient system in which one of the seven classical planets is given rulership over each day and various parts of the day. Developed in Hellenistic astrology, it has possible roots in older Babylonian astrology, and it is the origin of the names of the days of the week as used in English and numerous other languages.
Horrocks corrected Kepler's calculation for the orbit of Venus, realized that transits of Venus would occur in pairs 8 years apart, and so predicted the transit of 1639. [11] Although he was uncertain of the exact time, he calculated that the transit was to begin at approximately 15:00.
Inversely, for calculating the distance where a body has to orbit in order to have a given orbital period T: a = G M T 2 4 π 2 3 {\displaystyle a={\sqrt[{3}]{\frac {GMT^{2}}{4\pi ^{2}}}}} For instance, for completing an orbit every 24 hours around a mass of 100 kg , a small body has to orbit at a distance of 1.08 meters from the central body's ...
The calculation of precession and nutation was described in Chapter 6 of Urban & Seidelmann. As an example, the Astronomical Almanac for the Year 2017 gave the ERA at 0 h 1 January 2017 UT1 as 100° 37′ 12.4365″. The GAST was 6 h 43 m 20.7109 s. For GMST the hour and minute were the same but the second was 21.1060. [13]
That said, Venus and Earth still have the lowest gravitational potential difference between them than to any other planet, needing the lowest delta-v to transfer between them, than to any other planet from them. [12] [13] The distance between Venus and Mercury will become smaller over time primarily because of Mercury's increasing eccentricity.
Consequently, Venus transits above Earth only occur when an inferior conjunction takes place during some days of June or December, the time where the orbits of Venus and Earth cross a straight line with the Sun. [185] This results in Venus transiting above Earth in a sequence of currently 8 years, 105.5 years, 8 years and 121.5 years, forming ...
Venus, our closest planetary neighbor, is sometimes called Earth's twin based on their similar size and rocky composition. While its surface is baked and barren today, might Venus once also have ...
Point Venus Lighthouse, Tahiti (LMS, 1869, p.) [4]. In 1663, Scottish mathematician James Gregory came up with the idea of using Venus or Mercury transits to determine the astronomical unit by measuring the apparent solar parallax between different points on the surface of the Earth. [5]