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In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter (the combined center of mass) or, if one body is much more massive than the other bodies of the system combined, its speed relative to the center of mass of the most massive body.
When Pluto was discovered, it was considered a planet, and Neptune thus became the second-farthest known planet, except for a 20-year period between 1979 and 1999 when Pluto's elliptical orbit brought it closer than Neptune to the Sun, making Neptune the ninth planet from the Sun during this period.
Relative masses of the Solar planets. Jupiter at 71% of the total and Saturn at 21% dominate the system. Relative masses of the solid bodies of the Solar System. Earth at 48% and Venus at 39% dominate. Bodies less massive than Pluto are not visible at this scale. Relative masses of the rounded moons of the Solar System.
The table lists the values for all planets and dwarf planets, and selected asteroids, comets, and moons. Mercury has the greatest orbital eccentricity of any planet in the Solar System (e = 0.2056), followed by Mars of 0.093 4. Such eccentricity is sufficient for Mercury to receive twice as much solar irradiation at perihelion compared to aphelion.
In astronomy, Kepler's laws of planetary motion, published by Johannes Kepler between 1609 and 1619, describe the orbits of planets around the Sun. The laws modified the heliocentric theory of Nicolaus Copernicus, replacing its circular orbits and epicycles with elliptical trajectories, and explaining how planetary velocities vary.
Astrodynamics. 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.
If the Sun–Neptune distance is scaled to 100 meters (330 ft), then the Sun would be about 3 cm (1.2 in) in diameter (roughly two-thirds the diameter of a golf ball), the giant planets would be all smaller than about 3 mm (0.12 in), and Earth's diameter along with that of the other terrestrial planets would be smaller than a flea (0.3 mm or 0. ...
Type Escape velocity Mass Volume ()Lowest Highest Lowest Highest Lowest Highest Star: 617.7 km/s Sun. 332,830 M Earth Sun. 695,000 km Sun. Major planet: 4.3 k m/s Mercury: 59.5 km/s