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In astronomy, the rotation period or spin period [1] of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the sidereal rotation period (or sidereal day ), i.e., the time that the object takes to complete a full rotation around its axis relative to the background stars ( inertial space ).
The total mass of ice in Uranus's interior is not precisely known, because different figures emerge depending on the model chosen; it must be between 9.3 and 13.5 Earth masses. [ 17 ] [ 83 ] Hydrogen and helium constitute only a small part of the total, with between 0.5 and 1.5 Earth masses. [ 17 ]
As viewed from Earth during the year, the Sun appears to slowly drift along an imaginary path coplanar with Earth's orbit, known as the ecliptic, on a spherical background of seemingly fixed stars. [5] Each synodic day, this gradual motion is a little less than 1° eastward (360° per 365.25 days), in a manner known as prograde motion.
Earth's movement along its nearly circular orbit while it is rotating once around its axis requires that Earth rotate slightly more than once relative to the fixed stars before the mean Sun can pass overhead again, even though it rotates only once (360°) relative to the mean Sun. [n 5] Multiplying the value in rad/s by Earth's equatorial ...
What’s known about Uranus could be off the mark. An unusual cosmic occurrence during the Voyager 2 spacecraft’s 1986 flyby might have skewed how scientists characterized the ice giant, new ...
For example, the synodic period of the Moon's orbit as seen from Earth, relative to the Sun, is 29.5 mean solar days, since the Moon's phase and position relative to the Sun and Earth repeats after this period. This is longer than the sidereal period of its orbit around Earth, which is 27.3 mean solar days, owing to the motion of Earth around ...
A solar wind event squashed the protective bubble around Uranus just before Voyager 2 flew by the planet in 1986, shifting how astronomers understood the mysterious world.
Among Uranus's five major moons, Ariel is the second closest to the planet, orbiting at the distance of about 190,000 km. [f] Its orbit has a small eccentricity and is inclined very little relative to the equator of Uranus. [3] Its orbital period is around 2.5 Earth days, coincident with its rotational period.