148780 Altjira
Altjira and its companion imaged by the Hubble Space Telescope in 2006 | |
| Discovery | |
|---|---|
| Discovery site | Deep Ecliptic Survey at Kitt Peak |
| Discovery date | 20 October 2001 August 2006 (secondary) |
| Designations | |
| (148780) Altjira | |
| Pronunciation | /ælˈtʃɪrə/ |
| 2001 UQ18 | |
| Cubewano (DES) | |
| Adjectives | Altjirian |
| Orbital characteristics | |
| Epoch 13 January 2016 (JD 2457400.5) | |
| Uncertainty parameter 3 | |
| Observation arc | 2539 days (6.95 yr) |
| Aphelion | 46.877 AU (7.0127 Tm) |
| Perihelion | 41.572 AU (6.2191 Tm) |
| 44.224 AU (6.6158 Tm) | |
| Eccentricity | 0.059979 |
| 294.10 yr (107421 d) | |
| 124.29° | |
| 0.0033513°/day | |
| Inclination | 5.2056° |
| 2.0132° | |
| 297.71° | |
| Known satellites | 1 |
| Physical characteristics | |
| 331+51 −187 km (combined) 246+38 −139 km (primary) 221+34 −125 km (secondary) | |
| Mass | 3.952×1018 kg |
Mean density | 0.30+0.50 −0.14 g/cm3 |
| 0.0430+0.1825 −0.0095 | |
| B−V = 0.91±0.13 V−R = 0.74±0.08 V−I = 1.17±0.09 | |
| 5.7 5.6, 5.4, or 5.1 (primary) secondary's magnitude difference with primary's: 0.7 ± 0.2 | |
148780 Altjira /ælˈtʃɪrə/ is a triple or contact-binary double classical Kuiper belt object (cubewano). The secondary is large compared to the primary, approximately 246 kilometres (153 mi) vs. 221 kilometres (137 mi). The Altjiran lightcurve is quite flat (Δmag<0.10), which is indicative of a "quasi-spherical body with a homogeneous surface".
The satellite's orbit has the following parameters: semi-major-axis, 9904 ± 56 km; period, 139.561 ± 0.047 days; eccentricity, 0.3445 ± 0.0045; and inclination, 35.19 ± 0.19°(retrograde). The total system mass is about 4 × 1018 kg.
It was named after the Arrernte creation deity, Altjira, who created the Earth during the Dreamtime and then retired to the sky.
Altjira may be an unresolved hierarchical triple system.