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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 .
The accuracy of this calculation requires that the two dates chosen be along the elliptical orbit's minor axis and that the midpoints of each half be along the major axis. As the two dates chosen here are equinoxes, this will be correct when perihelion, the date the Earth is closest to the Sun, falls on a solstice. The current perihelion, near ...
The long orbital period of Neptune means that the seasons last for forty Earth years. [110] Its sidereal rotation period (day) is roughly 16.11 hours. [ 12 ] Because its axial tilt is comparable to Earth's, the variation in the length of its day over the course of its long year is not any more extreme.
Rotation period days: 25.38 Orbital period about Galactic Center [4] million years 225–250 Mean orbital speed [4] km/s: ≈ 220 Axial tilt to the ecliptic: deg. 7.25 Axial tilt to the galactic plane: deg. 67.23 Mean surface temperature: K: 5,778 Mean coronal temperature [5] K: 1–2 × 10 6: Photospheric composition H, He, O, C, Fe, S
Mercury, the closest planet to the Sun at 0.4 astronomical units (AU), takes 88 days for an orbit, but the smallest known orbits of exoplanets have orbital periods of only a few hours, see Ultra-short period planet. The Kepler-11 system has five of its planets in smaller orbits than Mercury's.
Finally, raw statistics from exoplanetary orbits strongly point to a general fulfillment of Titius-Bode-like laws (with exponential increase of semi-major axes as a function of planetary index) in all the exoplanetary systems; when making a blind histogram of orbital semi-major axes for all the known exoplanets for which this magnitude is known ...
The orbital period is equal to that for a circular orbit with the orbital radius equal to the semi-major axis (), For a given semi-major axis the orbital period does not depend on the eccentricity (See also: Kepler's third law).
In orbital mechanics, Kepler's equation relates various geometric properties of the orbit of a body subject to a central force.. It was derived by Johannes Kepler in 1609 in Chapter 60 of his Astronomia nova, [1] [2] and in book V of his Epitome of Copernican Astronomy (1621) Kepler proposed an iterative solution to the equation.