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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 .
This is because the distance between Earth and the Sun is not fixed (it varies between 0.983 289 8912 and 1.016 710 3335 au) and, when Earth is closer to the Sun , the Sun's gravitational field is stronger and Earth is moving faster along its orbital path. As the metre is defined in terms of the second and the speed of light is constant for all ...
The distance between Venus and Earth varies from about 42 million km (at inferior conjunction) to about 258 million km (at superior conjunction). The average period between successive conjunctions of one type is 584 days – one synodic period of Venus. Five synodic periods of Venus is almost exactly 13 sidereal Venus years and 8 Earth years ...
au is the distance for which k takes its value as defined by Gauss—the distance of the unperturbed circular orbit of a hypothetical, massless body whose orbital period is 2π / k days, [12] d is the mean solar day (86,400 seconds), M ☉ is the mass of the Sun. Therefore, the dimensions of k are [16] length 3 ⁄ 2 time −1 mass − ...
Its orbital eccentricity of 1.20 indicates that ʻOumuamua has never been gravitationally bound to the Sun. It was discovered 0.2 AU (30 000 000 km; 19 000 000 mi) from Earth and is roughly 200 meters in diameter. It has an interstellar speed (velocity at infinity) of 26.33 km/s (58 900 mph).
Radial velocity curve with peak radial velocity K=1 m/s and orbital period 2 years. The peak radial velocity is the semi-amplitude of the radial velocity curve, as shown in the figure. The orbital period is found from the periodicity in the radial velocity curve. These are the two observable quantities needed to calculate the binary mass function.
An orbit will be Sun-synchronous when the precession rate ρ = dΩ / dt equals the mean motion of the Earth about the Sun n E, which is 360° per sidereal year (1.990 968 71 × 10 −7 rad/s), so we must set n E = ΔΩ E / T E = ρ = ΔΩ / T , where T E is the Earth orbital period, while T is the period of the spacecraft ...
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.