This is a list of slow rotators—

minor planet According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term ''mino ...

s that have an exceptionally long rotation period. This period, typically given in hours, and sometimes called rotation rate or spin rate, is a fundamental standard physical property for minor planets. In recent years, the periods of many thousands of bodies have been obtained from photometric and, to a lesser extent,

radiometric Radiometry is a set of techniques for measuring electromagnetic radiation, including visible light. Radiometric techniques in optics characterize the distribution of the radiation's power in space, as opposed to photometric techniques, which ch ...

observations. The periods given in this list are sourced from the ''Light Curve Data Base'' (LCDB), which contains

lightcurve In astronomy, a light curve is a graph of light intensity of a celestial object or region as a function of time, typically with the magnitude of light received on the y axis and with time on the x axis. The light is usually in a particular freq ...

data for more than 15,000 bodies. Most minor planets have rotation periods between 2 and 20 hours. , a group of approximately 650 bodies, typically measuring 1–20

kilometer The kilometre ( SI symbol: km; or ), spelt kilometer in American English, is a unit of length in the International System of Units (SI), equal to one thousand metres (kilo- being the SI prefix for ). It is now the measurement unit used for ex ...

s in

diameter In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid fo ...

, have periods of more than 100 hours or 4 days. Among the slowest rotators, there are currently 15 bodies with a period longer than 1000 hours. According to the Minor Planet Center, the sharp lower limit of approximately 2.2 hours is due to the fact that most smaller bodies are thought to be

rubble pile In astronomy, a rubble pile is a celestial body that is not a monolith, consisting instead of numerous pieces of rock that have coalesced under the influence of gravity. Rubble piles have low density because there are large cavities between the ...

s – conglomerations of smaller pieces, loosely coalesced under the influence of gravity – that fly apart if the period is shorter than this limit. The few minor planets rotating faster than 2.2 hours, therefore, can not be merely held together by self-gravity, but must be formed of a contiguous solid. Potentially slow rotators have only an inaccurate period, estimated based on a fragmentary lightcurve and inconclusive measurement. They are listed separately from the more precise periods, which have a

LCDB quality code In astronomy, a light curve is a graph of light intensity of a celestial object or region as a function of time, typically with the magnitude of light received on the y axis and with time on the x axis. The light is usually in a particular frequ ...

, ''U'', of 2 or 3 (unambiguous result). The periods for potentially slow rotators may be completely wrong (''U'' = 1), have no complete and conclusive result (''U'' = n.a.), or large error margins of more than 30% (''U'' = 2−). A trailing plus sign (+) or minus sign (–) indicate slightly better or worse quality, respectively, than the unsigned value. As with orbital periods, a rotational period can be sidereal or synodic to describe a full rotation with respect to the fixed stars (sidereal) and

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

(synodic), respectively. In most cases, the periods given in this list are synodic, not sidereal. However, in most cases the difference between these two different measures is not significant. This is the case for all

main-belt The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies, of many sizes, but much smaller than planets, called ...

asteroids, which account for 97.5% of all minor planets.

Slowest rotators

This list contains the slowest-rotating minor planets with periods of at least 1000 hours, or 41 days. See ' for minor planets with an insufficiently accurate period—that is, a

of less than 2.

Periods between 500 and 1000 hours

Periods of 400+ hours

Periods of 300+ hours

Periods of 200+ hours

Periods of 100+ hours

Potentially slow rotators

Potentially slow rotators have their rotation period estimated based on a fragmentary light curve. They are listed separately from the more reliable results above, that have a quality code (U) of 2 or higher. The periods for potentially slow rotators may be completely wrong (U=1), have no complete and conclusive result (U=n.a.), a large error margins of more than 30% (U=2−), or anything in between.

Possible periods above 1000 hours

Possible periods between 500 and 1000 hours

Possible periods of 400+ hours

Possible periods of 300+ hours

Possible periods of 200+ hours

Possible periods of 100+ hours

References

External links

Asteroid Lightcurve Database (LCDB)
query form

– Observatoire de Genève, Raoul Behrend
Asteroid Lightcurve Photometry Database
''

Brian D. Warner This is a list of minor-planet discoverers credited by the Minor Planet Center with the discovery of one or several minor planets (such as near-Earth and main-belt asteroids, Jupiter trojans and distant objects). , the discovery of 612,011 numb ...

''
JPL Small-Body Database Browser
{{DEFAULTSORT:List of slow rotators * Slow rotators (minor planets) rotators, slow