| Discovery[1] | |
|---|---|
| Discovered by | H. E. Holt |
| Discovery site | Palomar Obs. |
| Discovery date | 29 July 1990 |
| Designations | |
| (9175) Graun | |
Named after | Ken Graun (American astronomy author)[2] |
| 1990 OO2 · 1975 CL 1980 BB1 · 1986 WS4 1991 XL2 | |
| main-belt Eunomia[3] · Maria[4] | |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 42.11 yr (15,382 days) |
| Aphelion | 2.9666AU |
| Perihelion | 2.2334 AU |
| 2.6000 AU | |
| Eccentricity | 0.1410 |
| 4.19yr (1,531 days) | |
| 159.53° | |
| 0° 14m 6.36s / day | |
| Inclination | 15.069° |
| 330.02° | |
| 353.26° | |
| Physical characteristics | |
| Dimensions | 7.929±0.142 km[5][6] 10.23±2.25 km[7] 10.35±0.71 km[8] 10.53 km(calculated)[3] |
| 20h[4] 25.8±0.5 h[9] | |
| 0.183±0.027[8] 0.20±0.09[7] 0.21(assumed)[3] 0.308±0.042[5][6] | |
| S[3] | |
| 12.2[1][3] · 12.25±0.38[10] · 12.4[8][5] · 12.66[7] | |
9175 Graun, provisional designation1990 OO2, is a stony Eunomianasteroid from the central region of theasteroid belt, approximately 10 kilometers in diameter. It was discovered on 29 July 1990, by American astronomerHenry E. Holt atPalomar Observatory in California, United States.[11] The asteroid was later named for American author and amateur astronomerKen Graun.[2]
Graun is a member of theEunomia family, a large group ofS-type asteroids and the most prominent family in theintermediate 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 aneccentricity of 0.14 and aninclination of 15° with respect to theecliptic.[1] In February 1975, it was first identified as1975 CL at theKarl Schwarzschild Observatory, extending the body'sobservation arc by 15 years prior to its official discovery observation at Palomar.[11]
Based on its concurring orbital elements,Graun has also been group into theMaria family, which is named after its namesake, the asteroid170 Maria.[4] It is an old-type asteroid family, about(3±1)×109 years old, located near the area of a 3:1resonances with Jupiter that supplies near-Earth asteroids to the innerSolar System. It is estimated that every 100 million years, about 37 to 75 Maria asteroids larger than 1 kilometer becomenear-Earth objects.[9]
In January 2013, a rotationallightcurve ofGraun was obtained from photometric observations. Lightcurve analysis gave arotation period of25.8 hours with a brightness variation of 0.16magnitude (U=2+).[9] The measurement supersedes a shorter period of 20 hours with an amplitude of 0.2 magnitude (U=1).[4]
According to the surveys carried out by theNEOWISE mission of NASA'sWide-field Infrared Survey Explorer and the JapaneseAkari satellite,Graun measures 10.23 and 10.35 kilometers in diameter, and its surface has analbedo of 0.20 and 0.183, respectively.[7][8] Preliminary NEOWISE results gave a much higher albedo and consequently shorter diameter.[5][6]
TheCollaborative Asteroid Lightcurve Link assumes an albedo of 0.21 – derived from15 Eunomia, the family's largest member and namesake – and calculates a diameter of 10.53 kilometers with anabsolute magnitude of 12.2.[3]
Thisminor planet 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 websiteWhat's Out tonight?, bringing astronomy to the broader public including children.[2][12] The official naming citation was published by theMinor Planet Center on 9 March 2001 (M.P.C. 42358).[13]
