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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 square of the period of the planet (one revolution around the Sun) is proportional to the cube of the average distance from the Sun. [73] In modern notation, = [73] where a is the radius of the orbit, T is the period, G is the gravitational constant and M is the mass of the Sun.
The Jupiter family is defined as comets that have a semi-major axis smaller than Jupiter's; most short-period comets belong to this group. Members of the Jupiter family are thought to form in the Kuiper belt outside the orbit of Neptune.
For example: q= 3×(length of Mars) + 2×(length of Jupiter). (The term 'length' in this context refers to the ecliptic longitude, that is the angle over which the planet has progressed in its orbit in unit time, so q is an angle over time too. The time needed for the length to increase over 360° is equal to the revolution period.)
A mean-motion orbital resonance occurs when two bodies have periods of revolution that are a simple integer ratio of each other. It does not depend only on the existence of such a ratio, and more precisely the ratio of periods is not exactly a rational number, even averaged over a long period.
Ganymede orbits Jupiter at a distance of 1,070,400 kilometres (665,100 mi), third among the Galilean satellites, [26] and completes a revolution every seven days and three hours (7.155 days [39]). Like most known moons, Ganymede is tidally locked, with one side always facing toward the planet, hence its day is also seven days and three hours. [40]
During the Renaissance Period, revolutionary ideas emerged about astronomy. One such idea was contributed in 1593 by Polish astronomer Nicolaus Copernicus, who developed a heliocentric model that depicted the planets orbiting the sun. This was the start of the Copernican Revolution. [3]
Jupiter's revolution period is 11.86 years, so Jupiter is called the "age star" (歲星; 岁星); 30° of Jupiter's revolution is about a year on earth. Saturn's revolution period is about 28 years. Known as the "guard star" , Saturn guards one of the 28 Mansions every year.