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  2. Planetary hours - Wikipedia

    en.wikipedia.org/wiki/Planetary_hours

    As each day is divided into 24 hours, the first hour of a day is ruled by the planet three places down in the Chaldean order from the planet ruling the first hour of the preceding day; [2] i.e. a day with its first hour ruled by the Sun ("Sunday") is followed by a day with its first hour ruled by the Moon ("Monday"), followed by Mars ("Tuesday ...

  3. Astronomical day - Wikipedia

    en.wikipedia.org/wiki/Astronomical_day

    The exact length has been variously defined as either that of a solar day or of a sidereal day. [ 1 ] [ 2 ] [ 3 ] Astronomical days were historically used by astronomers (in contrast most commonly to solar days), but since the Industrial Revolution this usage has generally fallen out of favor, in order to avoid confusion with more conventional ...

  4. Venus - Wikipedia

    en.wikipedia.org/wiki/Venus

    Because of the retrograde rotation, the length of a solar day on Venus is significantly shorter than the sidereal day, at 116.75 Earth days (making the Venusian solar day shorter than Mercury's 176 Earth days — the 116-day figure is close to the average number of days it takes Mercury to slip underneath the Earth in its orbit [the number of ...

  5. Sidereal time - Wikipedia

    en.wikipedia.org/wiki/Sidereal_time

    Mercury's sidereal day is about two-thirds of its orbital period, so by the prograde formula its solar day lasts for two revolutions around the Sun – three times as long as its sidereal day. Venus rotates retrograde with a sidereal day lasting about 243.0 Earth days, or about 1.08 times its orbital period of 224.7 Earth days; hence by the ...

  6. Orbit of Venus - Wikipedia

    en.wikipedia.org/wiki/Orbit_of_Venus

    Venus was 0.7205 au from the Sun on the day of transit, decidedly less than average. [ 9 ] Moving far backwards in time, more than 200,000 years ago Venus sometimes passed by at a distance from Earth of barely less than 38 million km, and will next do that after more than 400,000 years.

  7. Day - Wikipedia

    en.wikipedia.org/wiki/Day

    It uses the day as the base unit, and smaller units being fractions of a day: a metric hour (deci) is 1 ⁄ 10 of a day; a metric minute (milli) is 1 ⁄ 1000 of a day; etc. [16] Similarly, in decimal time, the length of a day is static to normal time. A day is also split into 10 hours, and 10 days comprise a décade – the equivalent of a ...

  8. Rotation period (astronomy) - Wikipedia

    en.wikipedia.org/wiki/Rotation_period_(astronomy)

    The other type of commonly used "rotation period" is the object's synodic rotation period (or solar day), which may differ, by a fraction of a rotation or more than one rotation, to accommodate the portion of the object's orbital period around a star or another body during one day.

  9. Synodic day - Wikipedia

    en.wikipedia.org/wiki/Synodic_day

    A synodic day (or synodic rotation period or solar day) is the period for a celestial object to rotate once in relation to the star it is orbiting, and is the basis of solar time. The synodic day is distinguished from the sidereal day , which is one complete rotation in relation to distant stars [ 1 ] and is the basis of sidereal time.