4951 Iwamoto, provisional designation , is a stony, synchronous

binary Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two digits (0 and 1) * Binary function, a function that takes two arguments * Binary operation, a mathematical operation that t ...

asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

and slow rotator from the

inner Interior may refer to: Arts and media * ''Interior'' (Degas) (also known as ''The Rape''), painting by Edgar Degas * ''Interior'' (play), 1895 play by Belgian playwright Maurice Maeterlinck * ''The Interior'' (novel), by Lisa See * Interior de ...

regions of the

asteroid 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 ...

, approximately 5.5 kilometers in diameter. It was discovered on 21 January 1990, by Japanese astronomers

Yoshikane Mizuno is a Japanese astronomer and co-discoverer of asteroids. The Minor Planet Center credits him with the discovery of 52 minor planets he made at the Kani Observatory () between 1989 and 1993. The inner main-belt asteroid 4541 Mizuno, discovered ...

and

Toshimasa Furuta is a Japanese astronomer. He is a prolific discoverer of asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in ...

at Kani Observatory () in Japan.

Orbit

''Iwamoto'' orbits the Sun in the

main-belt at a distance of 1.9–2.6 AU once every 3 years and 5 months (1,239 days). Its orbit has an

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-center, in geometry * Eccentricity (graph theory) of a v ...

of 0.17 and an

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

of 8 ° with respect to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic again ...

. It was first identified as at

Lowell Observatory Lowell Observatory is an astronomical observatory in Flagstaff, Arizona, United States. Lowell Observatory was established in 1894, placing it among the oldest observatories in the United States, and was designated a National Historic Landmark ...

in 1931, extending the body's

observation arc In observational astronomy, the observation arc (or arc length) of a Solar System body is the time period between its earliest and latest observations, used for tracing the body's path. It is usually given in days or years. The term is mostly use ...

by 59 years prior to its official discovery observation at Kani.

Physical characteristics

In the

SMASS classification An asteroid spectral type is assigned to asteroids based on their emission spectrum, color, and sometimes albedo. These types are thought to correspond to an asteroid's surface composition. For small bodies that are not internally differentiat ...

, ''Iwamoto'' is a common

S-type asteroid S-type asteroids are asteroids with a spectral type that is indicative of a siliceous (i.e. stony) mineralogical composition, hence the name. They have relatively high density. Approximately 17% of asteroids are of this type, making it the second ...

Diameter and albedo

According to the survey carried out by NASA's

Wide-field Infrared Survey Explorer Wide-field Infrared Survey Explorer (WISE, observatory code C51, Explorer 92 and SMEX-6) is a NASA infrared astronomy space telescope in the Explorers Program. It was launched in December 2009, and placed in hibernation mode in February 2011, ...

with its subsequent

NEOWISE Wide-field Infrared Survey Explorer (WISE, observatory code C51, Explorer 92 and SMEX-6) is a NASA infrared astronomy space telescope in the Explorers Program. It was launched in December 2009, and placed in hibernation mode in February 2011, ...

mission, ''Iwamoto'' measures 5.192 and 5.515 kilometers in diameter, and its surface has an

albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...

of 0.218 and 0.186, respectively. The ''Collaborative Asteroid Lightcurve Link'' adopts

Petr Pravec Petr Pravec (born September 17, 1967) is a Czech astronomer and a discoverer of minor planets, born in Třinec, Czech Republic. Pravec is a prolific discoverer of binary asteroids, expert in photometric observations and rotational lightcurves a ...

's revised WISE-data, that is, an albedo of 0.1844 and a diameter of 5.528 kilometers with on an

absolute magnitude Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse Logarithmic scale, logarithmic Magnitude (astronomy), astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent mag ...

of 13.74.

Slow rotator

From 25 December 2006 to 23 March 2007, photometric observations of ''Iwamoto'' were obtained by the international community of photometrists at Badlands Observatory (SD, USA),

Ondřejov Observatory The Ondřejov Observatory (; cs, Observatoř Ondřejov) is the principal observatory of the Astronomical Institute () of the Academy of Sciences of the Czech Republic. It is located near the village of Ondřejov, southeast of Prague, Czech R ...

(Czech Republic),

Modra Observatory The Astronomical Observatory of Modra ( sk, Astronomické observatórium Modra), also known as Modra Observatory or the Astronomical and Geophysical observatory in Modra, is an astronomical observatory located in Modra, Slovakia. It is owned and o ...

(Slovakia), Carbuncle Hill Observatory (RI, USA), Sonoita Research Observatory (AZ, USA), Kharkiv Observatory (Ukraine),

McDonald Observatory McDonald Observatory is an astronomical observatory located near unincorporated community of Fort Davis in Jeff Davis County, Texas, United States. The facility is located on Mount Locke in the Davis Mountains of West Texas, with additional facil ...

(TX, USA), Ironwood Observatory (HI, USA), Leura Observatory (Australia), Skalnaté pleso Observatory (Slovakia), Shed of Science Observatory (MN, USA),

Pic du Midi Observatory The Pic du Midi de Bigorre or simply the Pic du Midi (elevation ) is a mountain in the French Pyrenees. It is the site of the Pic du Midi Observatory. Pic du Midi Observatory The Pic du Midi Observatory (french: Observatoire du Pic du Mid ...

(France). Lightcurve analysis gave a

rotation period The rotation period of a celestial object (e.g., star, gas giant, planet, moon, asteroid) may refer to its sidereal rotation period, i.e. the time that the object takes to complete a single revolution around its axis of rotation relative to the ...

of 118 hours with a brightness variation of 0.34

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

(). In May 2011, astronomers Etienne Morelle,

Raoul Behrend 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 ...

obtained another lightcurve with a concurring period of 118 hours and an amplitude of 0.38 magnitude.(). With such a long period, ''Iwamoto'' is also a slow rotator, as the vast majority of asteroids have a much shorter rotation period of 2.2 to 20 hours.

Binary system

During the photometric observations in 2006/7, it was revealed that ''Iwamoto'' ("primary") is a synchronous

binary system A binary system is a system of two astronomical bodies which are close enough that their gravitational attraction causes them to orbit each other around a barycenter ''(also see animated examples)''. More restrictive definitions require that thi ...

with a

minor-planet moon A minor-planet moon is an astronomical object that orbits a minor planet as its natural satellite. , there are 457 minor planets known or suspected to have moons. Discoveries of minor-planet moons (and binary objects, in general) are important ...

("secondary") orbiting it every 4.917 days (or 118 hours, which identical to the primary's rotation). Based on the secondary-to-primary mean-diameter ratio (D_s/D_p) of at least 0.76, it was estimated that ''Iwamoto'' and its moon measure 4.0 and 3.5 kilometers, respectively. The diameter of ''Iwamoto'' has since increased to 5.5 kilometers ''(see above)''. The "Jonstonarchive" estimates that the moon has a

semi-major axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the long ...

of 31 kilometers.

Naming

This

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 ''minor ...

was named in honor of Japanese astronomer Masayuki Iwamoto (born 1954), a

discoverer of minor planets 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 ...

at the Tokushima Observatory (). The approved naming citation was published by the

Minor Planet Center The Minor Planet Center (MPC) is the official body for observing and reporting on minor planets under the auspices of the International Astronomical Union (IAU). Founded in 1947, it operates at the Smithsonian Astrophysical Observatory. Function ...

on 5 March 1996 ().

Orbit

Physical characteristics

Diameter and albedo

Slow rotator

Binary system

Naming

Notes

References

External links