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  2. Solar calendar - Wikipedia

    en.wikipedia.org/wiki/Solar_calendar

    The mean calendar year of such a calendar approximates the sidereal year. Leaping from one lunation to another, but one Sidereal year is the period between two occurrences of the sun, as measured by the stars' solar calendar, which is derived from the Earth's orbit around the sun every 28 years. [3]

  3. Rotation period (astronomy) - Wikipedia

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

    In astronomy, the rotation period or spin period [1] of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the sidereal rotation period (or sidereal day), i.e., the time that the object takes to complete a full rotation around its axis relative to the background stars (inertial space).

  4. Hindu calendar - Wikipedia

    en.wikipedia.org/wiki/Hindu_calendar

    Unlike the Gregorian calendar which adds additional days to the month to adjust for the mismatch between twelve lunar cycles (354 lunar days) [5] and approximately 365 solar days, the Hindu calendar maintains the integrity of the lunar month, but inserts an extra full month, once every 32–33 months, to ensure that the festivals and crop ...

  5. Analemma - Wikipedia

    en.wikipedia.org/wiki/Analemma

    The "width" of the figure is due to the equation of time, and its angular extent is the difference between the greatest positive and negative deviations of local solar time from local mean time when this time-difference is related to angle at the rate of 15° per hour, i.e., 360° in 24 h. This width of the analemma is approximately 7.7°, so ...

  6. Six planets are aligning this month. Here's the best time to ...

    www.aol.com/news/six-planets-aligning-month...

    Six planets will be in alignment during the planet parade: Mars, Jupiter, Uranus, Neptune, Venus, and Saturn. Uranus and Neptune won't appear as "bright planets," so you'll need a telescope or ...

  7. Solar time - Wikipedia

    en.wikipedia.org/wiki/Solar_time

    On a prograde planet like the Earth, the sidereal day is shorter than the solar day. At time 1, the Sun and a certain distant star are both overhead. At time 2, the planet has rotated 360° and the distant star is overhead again (1→2 = one sidereal day). But it is not until a little later, at time 3, that the Sun is overhead again (1→3 = one solar day). More simply, 1→2 is a complete ...

  8. Sidereal year - Wikipedia

    en.wikipedia.org/wiki/Sidereal_year

    At present, the rate of axial precession corresponds to a period of 25,772 years, [3] so sidereal year is longer than tropical year by 1,224.5 seconds (20 min 24.5 s, ~365.24219*86400/25772). Before the discovery of the precession of the equinoxes by Hipparchus in the Hellenistic period , the difference between sidereal and tropical year was ...

  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.