9175 Graun, provisional designation , is a stony Eunomian asteroid from the central region 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, c ...

, approximately 10 kilometers in diameter. It was discovered on 29 July 1990, by American astronomer

Henry E. Holt Henry E. Holt (27 September 1929 - 5 May 2019) was an American astronomer and prolific discoverer of minor planets and comets, who has worked as a planetary geologist at the United States Geological Survey and Northern Arizona University. Car ...

at Palomar Observatory in California, United States. The asteroid was later named for American author and amateur astronomer Ken Graun.

Orbit and classification

''Graun'' is a member of the

Eunomia family The Eunomia or Eunomian family () is a large asteroid family of S-type asteroids named after the asteroid 15 Eunomia. It is the most prominent family in the intermediate asteroid belt and the 6th-largest family with nearly six thousand known member ...

, a large group of

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 secon ...

s and the most prominent family in the intermediate main-belt. It orbits the Sun at a distance of 2.2–3.0 AU once every 4 years and 2 months (1,531 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-Centre (geometry), center, in geometry * Eccentricity (g ...

of 0.14 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 reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

of 15 ° 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 agains ...

. In February 1975, it was first identified as at the

Karl Schwarzschild Observatory The Karl Schwarzschild Observatory (german: Karl-Schwarzschild-Observatorium) is a German astronomical observatory in Tautenburg near Jena, Thuringia. It was founded in 1960 as an affiliated institute of the former German Academy of Sciences at ...

, 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 15 years prior to its official discovery observation at Palomar.

Alternative family

Based on its concurring orbital elements, ''Graun'' has also been group into the Maria family, which is named after its namesake, the asteroid 170 Maria. It is an old-type asteroid family, about years old, located near the area of a 3:1

resonances Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillat ...

with Jupiter that supplies near-Earth asteroids to the inner

Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...

. It is estimated that every 100 million years, about 37 to 75 Maria asteroids larger than 1 kilometer become

near-Earth object A near-Earth object (NEO) is any small Solar System body whose orbit brings it into proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU). ...

Physical characteristics

Lightcurves

In January 2013, 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 freq ...

of ''Graun'' was obtained from photometric observations. Lightcurve analysis gave a rotation period of hours with a brightness variation of 0.16

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 ...

(). The measurement supersedes a shorter period of 20 hours with an amplitude of 0.2 magnitude ().

Diameter and albedo

According to the surveys 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 201 ...

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 201 ...

and the Japanese

Akari Akari (ASTRO-F) was an infrared astronomy satellite developed by Japan Aerospace Exploration Agency, in cooperation with institutes of Europe and Korea. It was launched on 21 February 2006, at 21:28 UTC (06:28, 22 February JST) by M-V rocke ...

satellite, ''Graun'' measures 10.23 and 10.35 kilometers in diameter, and its surface has an

albedo Albedo (; ) is the measure of the diffuse reflection of 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 that refl ...

of 0.20 and 0.183, respectively. Preliminary NEOWISE results gave a much higher albedo and consequently shorter diameter. The ''Collaborative Asteroid Lightcurve Link'' assumes an albedo of 0.21 – derived from 15 Eunomia, the family's largest member and namesake – and calculates a diameter of 10.53 kilometers with an

absolute magnitude Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse logarithmic astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it ...

of 12.2.

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 ''mino ...

was named in honor of American amateur astronomer and publisher Ken Graun (born 1955), author of two books on astronomy, owner of "Ken Press" and the website ''What's Out tonight?'', bringing astronomy to the broader public including children. The official naming citation was published by the Minor Planet Center on 9 March 2001 ().

References

External links

Asteroid Lightcurve Database (LCDB)
query form

)
Dictionary of Minor Planet Names
Google books

– Observatoire de Genève, Raoul Behrend

– Minor Planet Center * * {{DEFAULTSORT:Graun 009175 009175 Discoveries by Henry E. Holt Named minor planets 19900729