.png) Light-curve-based 3D-model ofOnnie | |
| Discovery[1] | |
|---|---|
| Discovered by | H. van Gent |
| Discovery site | Johannesburg Obs. (Leiden Southern Station) |
| Discovery date | 28 September 1935 |
| Designations | |
| (1389) Onnie | |
Named after | A. Kruyt(relative of G. Pels)[2] |
| 1935 SS1 · 1949 QV1 1955 XB1 | |
| main-belt · Koronis[3] | |
| Orbital characteristics[1] | |
| Epoch 16 February 2017 (JD 2457800.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 80.87 yr (29,539 days) |
| Aphelion | 2.9118AU |
| Perihelion | 2.8183 AU |
| 2.8650 AU | |
| Eccentricity | 0.0163 |
| 4.85yr (1,771 days) | |
| 183.28° | |
| 0° 12m 11.52s / day | |
| Inclination | 2.0480° |
| 174.57° | |
| 297.53° | |
| Physical characteristics | |
| Dimensions | 12.46 km(derived)[3] 13.772±0.184 km[4] 14.737±0.159 km[5] |
| 22.5h[6] 23.0447±0.0005 h[7] | |
| 0.1734±0.0387[5] 0.198±0.016[4] 0.24(assumed)[3] | |
| B–V = 0.810[1] LS[8] · S[3][6] | |
| 11.64[1] · 11.69[3][5][6] · 11.74±0.40[8] | |
1389 Onnie, provisional designation1935 SS1, is a stony Koronianasteroid from the outer region of theasteroid belt, approximately 13 kilometers in diameter. It was discovered on 28 September 1935, by Dutch astronomerHendrik van Gent at Leiden Southern Station, annex to theJohannesburg Observatory in South Africa.[9]
The stonyS-type asteroid belongs to theKoronis family, a group consisting of few hundred known bodies with nearlyecliptical orbits.Onnie orbits the Sun at a distance of 2.8–2.9 AU once every 4 years and 10 months (1,771 days). Its orbit has aneccentricity of 0.02 and aninclination of 2° with respect to the ecliptic.[1]As noprecoveries were taken, and no prior identifications were made, the body'sobservation arc begins with its official discovery observation at Johannesburg.[9]
American astronomerRichard P. Binzel obtained a rotationallight-curve ofOnnie from photometric observations in September 1983. It gave a longer-than averagerotation period of 22.5 hours with a change in brightness of 0.34magnitude (U=2). In 2011 and 2013, respectively, a modeled light-curve using data from the Uppsala Asteroid Photometric Catalogue and other sources gave a period 23.0447 hours, as well as a spin axis of (183.0°, -75.0°) inecliptic coordinates (U=n.a.).[7][10]
According to the 2014-published result by NASA'sWide-field Infrared Survey Explorer with its subsequentNEOWISE mission,Onnie measures 13.77 kilometers in diameter, and its surface has analbedo of 0.198.[4] TheCollaborative Asteroid Lightcurve Link assumes a standard albedo for stony Koronian asteroids of 0.24 and derives a diameter of 12.46 kilometers based on an absolute magnitude of 11.69.[3]
Thisminor planet was named for A. Kruyt, sister-in-law of astronomer G. Pels (1893–1966). Pels, who proposed the minor planet's name, was as a lifelong member of theLeiden Observatory's staff, observer of minor planets at Leiden, as well as an orbit computer for many of Hendrik van Gent's made discoveries.[2] The minor planet1667 Pels was named in his honour.[11]
