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Five synodic periods of Venus is almost exactly 13 sidereal Venus years and 8 Earth years, and consequently the longitudes and distances almost repeat. [ 5 ] The 3.4° inclination of Venus's orbit is great enough to usually prevent the inferior planet from passing directly between the Sun and Earth at inferior conjunction.
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 ...
This approximate conjunction is not precise enough to produce a triplet, as Venus arrives 22 hours earlier each time. The last transit not to be part of a pair was in 1396 (the planet passed slightly above the disc of the Sun in 1388); [33] the next one will be in 3089. [citation needed] After 243 years the transits of Venus return.
The full cycle from new to full to new again takes 584 days (the time it takes Venus to overtake the Earth in its orbit). Venus (like the Moon) has 4 primary phases of 146 days each. The planet also changes in apparent size from 9.9 arc seconds at full (superior conjunction) up to a maximum of 68 arc seconds at new (inferior conjunction). [1]
The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy , it usually applies to planets or asteroids orbiting the Sun , moons orbiting planets, exoplanets orbiting other stars , or binary stars .
Sun-based: the year is based on the Earth's orbital period around the sun. Historical year-based units include the Olympiad (four years), the lustrum (five years), the indiction (15 years), the decade, the century, and the millennium. Moon-based: the month is based on the Moon's orbital period around the Earth.
In astronomy, an octaeteris (Greek: ὀκταετηρίς, plural: octaeterides) is the period of eight solar years after which the moon phase occurs on the same day of the year plus one or two days. This period is also in a very good synchronicity with five Venusian visibility cycles (the Venusian synodic period ) and thirteen Venusian ...
Notorious examples are the great Venus term and the Jupiter–Saturn great inequality. Looking up the revolution periods of these planets, one may notice that 8 × (period of Earth) is almost equal to 13 × (period of Venus) and 5 × (period of Jupiter) is about 2 × (period of Saturn).