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where v is the orbital velocity, ... Mercury's orbital speed varies from about 59 km/s at perihelion to 39 km/s at aphelion. [5] Orbital velocities of the Planets [6] ...
Mercury has an orbital speed of 47.4 km/s (29.5 mi/s), whereas Earth's orbital speed is 29.8 km/s (18.5 mi/s). [112] Therefore, the spacecraft must make a larger change in velocity ( delta-v ) to get to Mercury and then enter orbit, [ 187 ] as compared to the delta-v required for, say, Mars planetary missions .
Approximately four (Earth) days before perihelion, the angular speed of Mercury's orbit exactly matches its rotational velocity, so that the Sun's apparent motion stops. At perihelion, Mercury's orbital angular velocity slightly exceeds the rotational velocity, making the Sun appear to go retrograde.
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).
An object has reached escape velocity when the specific orbital energy is greater than or equal to zero. ... Mercury's gravity: 4.25 At Mercury: The Sun's gravity ...
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.
In 1894, Asaph Hall adopted this approach of modifying the exponent in the inverse-square law slightly to explain an anomalous orbital precession of the planet Mercury, [36] which had been observed in 1859 by Urbain Le Verrier. [37] Ironically, Hall's theory was ruled out by careful astronomical observations of the Moon. [38]
This third force causes the particle's elliptical orbit to precess (cyan orbit) in the direction of its rotation; this effect has been measured in Mercury, Venus and Earth. The yellow dot within the orbits represents the center of attraction, such as the Sun. The orbital precession rate may be derived using this radial effective potential V.