| Discovery[1] | |
|---|---|
| Discovered by | O. Oikawa K. Kubokawa |
| Discovery site | Tokyo Astronomical Obs. (389) |
| Discovery date | 1 December 1929 |
| Designations | |
| (1139) Atami | |
| Pronunciation | Japanese:[atami] |
Named after | Atami(Japanese city)[2] |
| 1929 XE | |
| Mars-crosser[1][3][4] | |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 87.50 yr (31,960 days) |
| Aphelion | 2.4451AU |
| Perihelion | 1.4505 AU |
| 1.9478 AU | |
| Eccentricity | 0.2553 |
| 2.72yr (993 days) | |
| 110.80° | |
| 0° 21m 45.36s / day | |
| Inclination | 13.087° |
| 213.35° | |
| 206.62° | |
| Knownsatellites | 1[5] |
| Earth MOID | 0.4722 AU · 184LD |
| Mars MOID | 0.0298 AU |
| Physical characteristics | |
| Dimensions | 8.24±0.82 km[6] 9.35 km(calculated)[4] |
| 15h[7] 20 h[8] 24 h[9] 27.43±0.05[9] 27.446±0.001 h[9] 27.45±0.01 h[9] 27.45±0.05 h[9] 27.472±0.002 h[9] 27.56±0.01 h[10][a] | |
| 0.20(assumed)[4] 0.258±0.052[6] | |
| S(Tholen)[1] · S(SMASS)[1][4] S[11] B–V = 0.920[1] U–B = 0.497[1] | |
| 12.51[1][4][6] · 12.59±0.37[11] · 12.86±0.02[7] | |
1139 Atami, provisional designation1929 XE, is a stonyasteroid and sizableMars-crosser, as well as a synchronousbinary system[5] near the innermost region of theasteroid belt, approximately 9 kilometers in diameter. It was discovered on 1 December 1929, by Japanese astronomersOkuro Oikawa andKazuo Kubokawa at the Tokyo Astronomical Observatory (389) near Tokyo.[3] It was named after the Japanese city ofAtami.[2] It has the lowestMinimum orbit intersection distance (MOID) toMars of any asteroid as large as it, its orbit intersecting only 0.03 astronomical units from the planet.
Atami is aMars-crossing asteroid, a dynamically unstable group between the main belt and thenear-Earth populations, crossing the orbit of Mars at 1.666 AU. It orbits the Sun at a distance of 1.5–2.4 AU once every 2 years and 9 months (993 days). Its orbit has aneccentricity of 0.26 and aninclination of 13° with respect to theecliptic.[1] The body'sobservation arc begins with its official discovery observation at Tokyo in 1929.[3]
Atami is a common stonyS-type asteroid in both theTholen andSMASS classification.[1] It has also been characterized as a S-type byPan-STARRS photometric survey.[11]
In 2005, two rotationallightcurves obtained at the U.S. Antelope Hills Observatory in New Mexico and by a collaboration of several European astronomers gave arotation period of27.56±0.01 and27.446±0.001 hours with a brightness variation of 0.45 and 0.40 inmagnitude, respectively (U=3/3).[9][10][a]
Photometric andArecibo echo spectra observations in 2005 confirmed a 5 kilometer satellite orbiting at least 15 kilometers from its primary.[5] Due to the similar size of the primary and secondary theMinor Planet Center lists this as abinary companion.[12]
According to the survey carried out by NASA'sWide-field Infrared Survey Explorer and its subsequentNEOWISE mission,Atami measures 8.24 kilometers in diameter and its surface has analbedo of 0.258,[6] while theCollaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 9.35 kilometers based on anabsolute magnitude of 12.51.[4]
This makesAtami one of the largest mid-sizedMars-crossing asteroids comparable with1065 Amundsenia (9.75 km),1474 Beira (8.73 km),1011 Laodamia (7.5 km),1727 Mette (est. 9 km),1131 Porzia (7.13 km),1235 Schorria (est. 9 km),985 Rosina (8.18 km),1310 Villigera (15.24 km) and1468 Zomba (7 km), but far smaller than the largest members of this dynamical group, namely,132 Aethra,323 Brucia,1508 Kemi,2204 Lyyli and512 Taurinensis, which are all larger than 20 kilometers in diameter.
Theminor planet was named afterAtami, a Japanese city and harbor near Tokyo, Japan.[2] The naming citation was first mentioned inThe Names of the Minor Planets byPaul Herget in 1955 (H 106).[2]
