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Encyclopedia > Rotation period

In astronomy, a rotation period is the time an astronomical object takes to complete one revolution around its rotation axis relative to the background stars. For the Earth this is a sidereal day. It differs from a solar day, which is measured by the passage of the Sun across the local meridian. A giant Hubble mosaic of the Crab Nebula, a supernova remnant Astronomy (also frequently referred to as astrophysics) is the scientific study of celestial objects (such as stars, planets, comets, and galaxies) and phenomena that originate outside the Earths atmosphere (such as the cosmic background radiation). ... A pocket watch, a device used to tell time Look up time in Wiktionary, the free dictionary. ... A giant Hubble mosaic of the Crab Nebula, a supernova remnant Astronomy (also frequently referred to as astrophysics) is the scientific study of celestial objects (such as stars, planets, comets, and galaxies) and phenomena that originate outside the Earths atmosphere (such as the cosmic background radiation). ... Astronomical objects are significant physical entities, associations or structures which current science has confirmed to exist in space. ... The axis of rotation of a rotating body is a line such that the distance between any point on the line and any point of the body remains constant under the rotation. ... On a prograde planet like the Earth, the sidereal day is shorter than the solar day. ... Solar time is based on the idea that, when the sun reaches its highest point in the sky, it is noon. ... The Sun (Latin: Sol) is the star at the center of the Solar System. ... On the earth, a meridian is a north-south line between the North Pole and the South Pole. ...

Contents

Measuring rotation

For solid objects, such as rocky planets and asteroids, the rotation period is a single value. For gaseous/fluid bodies, such as stars and gas giant planets, the period of rotation varies from the equator to the poles due to a phenomenon called differential rotation. Typically, the stated rotation period for a gas giant (i.e., Jupiter) is the internal rotation period, as determined from the rotation of the planet's magnetic field. For objects that are not spherically symmetrical, the rotation period is in general not fixed, even in the absence of gravitational or tidal forces. This is because, although the rotation axis is fixed in space (by the conservation of angular momentum), it is not necessarily fixed in the body of the object itself. The moment of inertia of the object around the rotation axis can therefore vary, and hence the rate of rotation can vary (because the product of the moment of inertia and the rate of rotation is equal to the angular momentum, which is fixed). Hyperion, a satellite of Saturn, exhibits this behaviour, and its rotation period is described as chaotic. A planet (from the Greek πλανήτης, planetes or wanderers) is a body of considerable mass that orbits a star and that produces very little or no energy through nuclear fusion. ... Asteroids is a popular vector-based video arcade game released in 1979 by Atari. ... STARS can mean: Shock Trauma Air Rescue Society Special Tactics And Rescue Service, a fictional task force that appears in Capcoms Resident Evil video game franchise. ... This article does not cite any references or sources. ... Differential rotation is seen if parts of a rotating object move with different angular velocity. ... Magnetic field lines shown by iron filings In physics, a magnetic field is a solenoidal vector field in the space surrounding moving electric charges and magnetic dipoles, such as those in electric currents and magnets. ... A sphere is a perfectly symmetrical geometrical object. ... Sphere symmetry group o. ... Gravity is a force of attraction that acts between bodies that have mass. ... Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiters tidal forces. ... In physics, angular momentum intuitively measures how much the linear momentum is directed around a certain point called the origin; the moment of momentum. ... Moment of inertia, also called mass moment of inertia and, sometimes, the angular mass, (SI units kg m², Former British units slug ft2), is the rotational analog of mass. ... Hyperion (IPA: , Greek Ὑπερίων) is a moon of Saturn discovered by William Cranch Bond, George Phillips Bond and William Lassell in 1848. ... Adjectives: Saturnian Atmosphere [2] Composition: ~96% molecular hydrogen ~3% Helium ~0. ... A plot of the Lorenz attractor for values r = 28, σ = 10, b = 8/3 In mathematics and physics, chaos theory describes the behavior of certain nonlinear dynamical systems that under specific conditions exhibit dynamics that are sensitive to initial conditions (popularly referred to as the butterfly effect). ...


Rotation period is different from period of revolution, which is the amount of time it takes one object to complete one orbit around a second object. Thus, the earth has a rotation period of about 24 hours, and a period of revolution of about 365 days. On the other hand, earth's moon has a rotation period that is exactly equal to its period of revolution around the earth, since the same side of the moon always faces the earth; this is called synchronous rotation.


Both predicting and recording the passage of these motions is facilitated by the use of calendars. The number of earth days in an earth year (rotations per revolution) is not a convenient whole number, approximating 365.24 days per year. To reconcile the widely used Gregorian calendar, leap seconds, leap years, and leap centuries (a special case of the leap year that occurs once every 400 years) are needed. Other calendars use other strategies or simply ignore the issue. The Gregorian calendar is the most widely used calendar in the world. ... A leap second is a one-second adjustment to civil time in order to keep it close to the mean solar time. ... A leap year (or intercalary year) is a year containing an extra day (or, in case of lunisolar calendars, an extra month) in order to keep the calendar year synchronised with the astronomical or seasonal year. ... A leap year (or intercalary year) is a year containing an extra day (or, in case of lunisolar calendars, an extra month) in order to keep the calendar year synchronised with the astronomical or seasonal year. ...


Rotation period of selected objects

Planet Rotation Period
Sun 25 days 9 hours 7 minutes 13 seconds (25.38 days) (equator), about 35 days near the poles
Mercury 58 days 15.5088 hours (58.6462 days)
Venus 243.0185 days
Earth 0.997270 days (23.93447 hours or 86,164 seconds)
Earth's Moon 27.321661 days (synchronous)
Mars 24.622962 hours (1.025 957 days)
Jupiter 9 hours 55 minutes 29.685 seconds (0.413538021 days)
Saturn 10 hours 39 minutes 22.4 seconds (0.4440092592 days)
Uranus 17 hours 14 minutes 24 seconds (0.718333333 days)
Neptune 16 hours 6 minutes 36 seconds (0.67125000 days)
Pluto 6 days 9 hours 17.6 minutes (6.387 days)

The Sun (Latin: Sol) is the star at the center of the Solar System. ... This article is about the planet. ... (*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ... This article is about Earth as a planet. ... Apparent magnitude: up to -12. ... In astronomy, synchronous rotation is a planetological term describing a body orbiting another, where the orbiting body takes as long to rotate on its axis as it does to make one orbit; and therefore always keeps the same hemisphere pointed at the body it is orbiting. ... Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... Atmospheric characteristics Atmospheric pressure 140 kPa Hydrogen >93% Helium >5% Methane 0. ... Atmospheric characteristics Atmospheric pressure 120 kPa Hydrogen 83% Helium 15% Methane 1. ... Atmospheric characteristics Surface pressure ≫100 MPa Hydrogen - H2 80% ±3. ... Atmospheric characteristics Atmospheric pressure 0. ...

See also

The orbital period is the time it takes a planet (or another object) to make one full orbit. ... Sidereal time is time measured by the apparent diurnal motion of the vernal equinox, which is very close to, but not identical with, the motion of stars. ... In astronomy, synchronous rotation is a planetological term describing a body orbiting another, where the orbiting body takes as long to rotate on its axis as it does to make one orbit; and therefore always keeps the same hemisphere pointed at the body it is orbiting. ... Prograde motion is the motion of a planetary body in a direction similar to that of other bodies within its system, and is sometimes called direct motion, especially in astrology. ... Precession of a gyroscope Precession refers to a change in the direction of the axis of a rotating object. ...

Sources


  Results from FactBites:
 
Rotation Period and Day Length (2489 words)
As a result, the rotation period of a planet which has a retrograde rotation is a negative number, as shown in the table for the three planets which have such a rotation.
To explain why the day length, or synodic period of rotation, is different from the sidereal period of rotation, we consider how a given place moves around a planet, and the way in which this changes its view of the sky, during one rotation period.
Since these objects are rotating slowly, it takes them a long time to rotate through that large angle, and during that time, their orbital motions carry them through a substantial additional angle, making the difference between the rotation period and the day length even greater.
  More results at FactBites »

 
 

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