6247 Amanogawa, provisional designation , is a background

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. ...

from the inner 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 in diameter. It was discovered on 21 November 1990, by Japanese amateur astronomers

Kin Endate is a Japanese amateur astronomer who has discovered hundreds of asteroids, most of them in collaboration with Kazuro Watanabe, placing him among the most prolific discoverers of minor planets. Career in astronomy Kin Endate was born in Iwa ...

and

Kazuro Watanabe is a Japanese amateur astronomer and prolific discoverer of minor planets. He was born in Hokkaidō, Japan and is a member of the ''Astronomical Society of Japan'' as well as of the ''Oriental Astronomical Association''. Through publications ...

at the

Kitami Observatory Kitami Observatory is an astronomical observatory in the Kitami-Abashiri Region Cultural Centre in eastern Hokkaidō, Japan. Its observatory code is 400. It is 0.72344 Earth radii from the rotation axis and +0.68811 Earth radii from the equatorial ...

. The

X-type asteroid The X-group of asteroids collects together several types with similar spectra, but probably quite different compositions. Tholen classification In the Tholen classification the X-group consists of the following types: * E-type – with high al ...

has 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 12.38 hours. It was named after the

Amanogawa River The Amanogawa ( ja, 天の川), Amano-gawa or Amano is a river in Japan, which passes through Hirakata, near Osaka. The name means "heavenly river", and is also the Japanese name for the Milky Way. The river empties into the Yodo River The , ...

on the island of Hokkaido, Japan.

Orbit and classification

''Amanogawa'' is a non-

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

asteroid from the main belt's background population. It orbits the Sun in 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 ...

asteroid belt at a distance of 2.3–2.5 AU once every 3 years and 9 months (1,353 days;

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 2.39 AU). 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 0.06 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 9 ° 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 ...

. 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 ...

begins with a

precovery In astronomy, precovery (short for pre-discovery recovery) is the process of finding the image of an object in images or photographic plates predating its discovery, typically for the purpose of calculating a more accurate orbit. This happens mos ...

Palomar Observatory Palomar Observatory is an astronomical research observatory in San Diego County, California, United States, in the Palomar Mountain Range. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observat ...

on 14 November 1990, just one week prior to its official discovery observation at Kitami.

Physical characteristics

In the SDSS-based taxonomy, ''Amanogawa'' has been characterized as an

. It is also a generically assumed

C-type asteroid C-type (carbonaceous) asteroids are the most common variety, forming around 75% of known asteroids. They are volatile-rich and distinguished by a very low albedo because their composition includes a large amount of carbon, in addition to rocks ...

Rotation period

In September 2008, a rotational

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 frequ ...

of ''Amanogawa'' was obtained from photometric observations at the

Oakley Southern Sky Observatory This is a list of observatory codes (IAU codes or MPC codes) published by the Minor Planet Center. For a detailed description, ''see observations of small Solar System bodies Observations of minor planets as well as comets and natural satellites ...

and

Oakley Observatory Oakley Observatory or Rose–Hulman Observatory ( Obs. code: 916) is an astronomical observatory operated by Rose–Hulman Institute of Technology in Terre Haute, Indiana, United States. The Oakley Observatory is a teaching observatory w ...

. Lightcurve analysis gave a well-defined

of 12.38 hours with a brightness variation of 0.48

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 February 2014, astronomers at the

Palomar Transient Factory The Palomar Transient Factory (PTF, obs. code: I41), was an astronomical survey using a wide-field survey camera designed to search for optical transient and variable sources such as variable stars, supernovae, asteroids and comets. The projec ...

measured a similar period of 12.369 hours and an amplitude of 0.38 magnitude in the R-band ().

Diameter and albedo

According to the survey carried out by the

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 of 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, ...

, ''Amanogawa'' measures 6.722 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 0.165. The ''Collaborative Asteroid Lightcurve Link'' assumes a standard albedo for a

carbonaceous Carbon () is a chemical element with the chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—its atom making four electrons available to form covalent bond, covalent chemical bonds. It belongs to gro ...

asteroid of 0.057 and calculates a diameter of 11.63 kilometers based 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 13.4.

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 after the Japanese

that through the town of Kaminokuni on the island of Hokkaido. "Amanogawa" also means "Milky Way" in Japanese. The official 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 22 February 1997 ().

References

External links

Asteroid Lightcurve Database (LCDB)
query form

)
Dictionary of Minor Planet Names
Google books

– Minor Planet Center * * {{DEFAULTSORT:Amanogawa 006247 Discoveries by Kazuro Watanabe Discoveries by Kin Endate Named minor planets 19901121