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An increase of 360° in the ERA is a full rotation of the Earth. A sidereal day on Earth is approximately 86164.0905 seconds (23 h 56 min 4.0905 s or 23.9344696 h). (Seconds are defined as per International System of Units and are not to be confused with ephemeris seconds.)
A synodic day (or synodic rotation period or solar day) is the period for a celestial object to rotate once in relation to the star it is orbiting, and is the basis of solar time. The synodic day is distinguished from the sidereal day, which is one complete rotation in relation to distant stars [1] and is the basis of sidereal time.
The other type of commonly used "rotation period" is the object's synodic rotation period (or solar day), which may differ, by a fraction of a rotation or more than one rotation, to accommodate the portion of the object's orbital period around a star or another body during one day.
The long orbital period of Neptune means that the seasons last for forty Earth years. [109] Its sidereal rotation period (day) is roughly 16.11 hours. [ 12 ] Because its axial tilt is comparable to Earth's, the variation in the length of its day over the course of its long year is not any more extreme.
On a prograde planet like the Earth, the sidereal day is shorter than the solar day. At time 1, the Sun and a certain distant star are both overhead. At time 2, the planet has rotated 360° and the distant star is overhead again (1→2 = one sidereal day). But it is not until a little later, at time 3, that the Sun is overhead again (1→3 = one solar day). More simply, 1→2 is a complete ...
The radio instruments on board found that Neptune's day lasts 16 hours and 6.7 minutes. Neptune's rings had been observed from Earth many years prior to Voyager 2 's visit, but the close inspection revealed that the ring systems were full circle and intact, and a total of four rings were counted. [4] Voyager 2 discovered six new small moons ...
Known affectionately to scientists as the "boring billion," there was a seemingly endless period in the world's history when the length of a day stayed put. The time when a day on Earth was just ...
It may also refer to the time it takes a satellite orbiting a planet or moon to complete one orbit. For celestial objects in general, the orbital period is determined by a 360° revolution of one body around its primary, e.g. Earth around the Sun. Periods in astronomy are expressed in units of time, usually hours, days, or years.