Rotation period

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Rotation period

The rotation period of an astronomical

Astronomy

Astronomy is the science of Astronomical object and Phenomenon that originate outside the Earth's atmosphere . It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the physical cosmology....
object

Astronomical object

s are significant entity, associations or structures which current science has confirmed to exist in outer space. This does not necessarily mean that more current science will not disprove their existence....
is the time it takes to complete one revolution around its axis of rotation relative to the background stars. It differs from the planet's solar day, which includes an extra fractional rotation needed to accommodate the portion of the planet's orbital period

Orbital period

The orbital Periodicity is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars....
during one day.

solid objects, such as rocky planets and asteroids, the rotation period is a single value.

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Encyclopedia

The rotation period of an astronomical

Astronomy

Astronomical object

Orbital period

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

STARS

STARS can mean:*Fulton surface-to-air recovery system*Shock Trauma Air Rescue Society*STARS members in Resident Evil, a fictional task force that appears in Capcom's Resident Evil video game franchise....
and gas giant

Gas giant

A gas giant is a large planet that is not primarily composed of Rock or other solid matter. There are four gas giants in our Solar System: Jupiter, Saturn, Uranus, and Neptune....
planets, the period of rotation varies from the equator to the poles due to a phenomenon called differential rotation

Differential rotation

Differential rotation is seen when different parts of a rotating object move with different angular velocity . This indicates that the object is not solid....
. Typically, the stated rotation period for a gas giant (Jupiter, Saturn, Uranus, Neptune) is its internal rotation period, as determined from the rotation of the planet's magnetic field

Magnetic field

A magnetism field is a vector field which can exert a magnetic force on moving electric charges and on magnetic dipoles . When placed in a magnetic field, magnetic dipoles tend to align their axes parallel to the magnetic field....
. For objects that are not spherically

Sphere

A sphere is a symmetrical geometrical object. In non-mathematical usage, the term is used to refer either to a round ball or to its two-dimensional surface....
symmetrical

Symmetry

Symmetry generally conveys two primary meanings. The first is an imprecise sense of harmonious or aesthetically-pleasing proportionality and balance; such that it reflects beauty or perfection....
, the rotation period is in general not fixed, even in the absence of gravitational or tidal

Tidal force

The tidal force is a secondary effect of the force of gravity and is responsible for the tides. It arises because the gravitational force exerted on one body by a second body is not constant across its diameter....
forces. The moment of inertia

Moment of inertia

Moment of inertia, also called mass moment of inertia or the angular mass, is a measure of an object's resistance to changes in its rotation rate....
of the object around the rotation axis can 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

Hyperion (moon)

'Hyperion' is a natural satellite of Saturn discovered by William Cranch Bond, George Phillips Bond and William Lassell in 1848. It is distinguished by its irregular shape, its chaotic rotation, and its unexplained sponge-like appearance....
, a satellite of Saturn

Saturn

Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn, along with Jupiter, Uranus and Neptune, is classified as a gas giant....
, exhibits this behaviour, and its rotation period is described as chaotic

Chaos theory

In mathematics, chaos theory describes the behavior of certain dynamical system s ? that is, systems whose states evolve with time ? that may exhibit dynamics that are highly sensitive to initial conditions ....
.

Earth

Earth's rotation period relative to the Sun (its mean solar day) is 86,400 second

Second

The second , sometimes abbreviated sec., is the name of a units of measurement of time, and is the International System of Units SI base unit of time....
s of mean solar time. Each of these seconds is slightly longer than an SI

Si, si, or SI may refer to :...
second because Earth's solar day is now slightly longer than it was during the 19th century due to tidal acceleration

Tidal acceleration

Tidal acceleration is an effect of the tidal forces between an orbiting natural satellite , and the planet that it orbits. The "acceleration" is usually negative, as it causes a gradual slowing and recession of a satellite in a prograde orbit away from the primary, and a corresponding slowdown of the primary's rotation....
. The mean solar second between 1750 and 1892 was chosen in 1895 by Simon Newcomb

Simon Newcomb

Simon Newcomb was a Canadaian-U.S. astronomer and mathematician. Though he had little conventional schooling, he made important contributions to timekeeping as well as writing on economics, statistics and authoring a science fiction novel....
as the independent unit of time in his Tables of the Sun

Newcomb's Tables of the Sun

Newcomb's Tables of the Sun is the short title for a work by the United States astronomer and mathematician Simon Newcomb entitled "Tables of the Motion of the Earth on its Axis and Around the Sun" on pages 1-169 of "Tables of the Four Inner Planets" , volume VI of the serial publication Astronomical Papers prepared for the use of the A...
. These tables were used to calculate the world's ephemerides

Ephemeris

An ephemeris is a table of values that gives the positions of astronomical objects in the sky at a given time or times. Different kinds are used for astronomy and astrology....
between 1900 and 1983, so this second became known as the ephemeris second. The SI second was made equal to the ephemeris second in 1967.

Earth's rotation period relative to the fixed star

Fixed star

.The fixed stars are celestial objects that do not seem to move in relation to the other stars of the night sky. Hence, a fixed star is any star except for the Sun....
s, called its stellar day by the International Earth Rotation and Reference Systems Service

International Earth Rotation and Reference Systems Service

The International Earth Rotation and Reference Systems Service , formerly the International Earth Rotation Service, is the body responsible for maintaining global time and Frame of reference standards, notably through its Earth Orientation Parameter and International Celestial Reference System groups....
(IERS), is seconds of mean solar time (UT1) Earth's rotation period relative to the precessing or moving mean vernal equinox

Equinox

Equinoxes occur twice a year, when the tilt of the Earth's axis is inclined neither away from nor toward the Sun, causing the Sun to be located vertically above a point on the equator....
, misnamed its sidereal day, is seconds of mean solar time (UT1) Thus the sidereal day is shorter than the stellar day by about 8.4 ms. The length of the mean solar day in SI seconds is available from the IERS for the periods 1623–2005 and 1962–2005. Recently (1999–2005) the average annual length of the mean solar day in excess of 86400 SI seconds has varied between 0.3 ms and 1 ms, which must be added to both the stellar and sidereal days given in mean solar time above to obtain their lengths in SI seconds.

Rotation period of selected objects

Planet	Rotation period
Sun Sun The Sun , a G V star, is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 98.6% of the Solar System's mass....	25.379995 days (equatorial) 35 days (high latitude)	35
Mercury Mercury (planet) Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 88 days. The orbit of Mercury has the highest Orbital eccentricity of all the Solar System planets, and it has the smallest axial tilt....	58.6462 days
Venus Venus Venus is the second-closest planet to the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus , the Roman mythology goddess of love....	–243.0187 days
Earth Earth Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Wiktionary:Terra.Note that by International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather...	0.99726968 days
Moon Moon The Moon is Earth's only natural satellite and the List of natural satellites by diameter satellite in the Solar System. The average centre-to-centre distance from the Earth to the Moon is km, about thirty times the diameter of the Earth....	27.321661 days (synchronous Synchronous rotation In astronomy, *synchronous rotation* is a planetology term describing a body orbit another, where the orbiting body takes as long to rotate on its axis of rotation as it does to make one orbit; and therefore always keeps the same hemisphere pointed at the body it is orbiting.... toward Earth)
Mars MARS In cryptography, MARS is a block cipher that was IBM's submission to the Advanced Encryption Standard process. MARS was selected as an AES finalist in August 1999, after the AES2 conference in March 1999, where it was voted as the fifth and last finalist algorithm....	1.02595675 days
Ceres	0.37809 days
Jupiter Jupiter Jupiter is the fifth planet from the Sun and the Solar system by size planet within the Solar System. It is two and a half times as massive as all of the other planets in our Solar System combined....	0.4135344 days (deep interior) 0.41007 days (equatorial) 0.41369942 days (high latitude)	0 9 50 30 0 9 55 43.63
Saturn Saturn Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn, along with Jupiter, Uranus and Neptune, is classified as a gas giant....	0.44403 days (deep interior) 0.426 days (equatorial) 0.443 days (high latitude)	0 10 14 0 10 38
Uranus Uranus Uranus is the seventh planet from the Sun and the third-largest and fourth most massive planet in the Solar System. It is named after the ancient Greek deity of the sky Uranus the father of Kronos and grandfather of Zeus ....	–0.71833 days
Neptune NEPTUNE =Overview=The project, along with sister project, VENUS, offers a unique approach to ocean science. Traditionally, ocean scientists have relied on infrequent ship cruises or space-based satellites to carry out their research....	0.67125 days
Pluto Pluto Pluto , Minor planet names Pluto, is the second-largest known dwarf planet in the Solar System and the tenth-largest body observed directly orbiting the Sun....	–6.38718 days (synchronous with Charon Charon (moon) 'Charon' , discovered in 1978, is the largest moon of the dwarf planet Pluto. Following the 2005 discovery of two other natural satellites of Pluto , Charon may also referred to as 'Pluto I'.... )
Haumea	0.163145 days

External links

Rotation periods of Mercury and Earth are wrong.

Rotation period

Measuring rotation

Earth

Rotation period of selected objects

See also

External links