148780 Altjira /ælˈtʃɪrə/ is a binary classical Kuiper belt object (cubewano).[2] The secondary, S/2007 (148780) 1, is large compared to the primary, 140 kilometres (87 mi) vs. 160 kilometres (99 mi).[4] The Altjiran lightcurve is quite flat (Δmag<0.10), which is indicative of a "quasi-spherical body with a homogeneous surface".[5]
Altjira and its companion imaged by the Hubble Space Telescope in 2006
| |
| Discovery | |
|---|---|
| Discovery site | Deep Ecliptic SurveyatKitt Peak[1] |
| Discovery date | 20 October 2001 August 2006 (secondary)[2] |
| Designations | |
| (148780) Altjira | |
| Pronunciation | /ælˈtʃɪrə/ |
| 2001 UQ18 | |
| Cubewano (DES)[3] | |
| Adjectives | Altjirian |
| Orbital characteristics[1] | |
| Epoch 13 January 2016 (JD 2457400.5) | |
| Uncertainty parameter3 | |
| 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 | |
| Dimensions | ≈128–200 (primary)[4] and 100–180 km (secondary) |
| Mass | 3.952×1018kg[4] |
Mean density | 0.5–2.0 g/cm3[4] |
| 0.06–0.14[4] | |
| 5.7[1] 5.6,[5] 5.4,[2] or 5.1[2] (primary) secondary's magnitude difference with primary's: 0.7 ± 0.2[2] | |
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.[4]
It was named after the Arrernte creation deity, Altjira, who created the Earth during the Dreamtime and then retired to the sky.[1]
Altjira may be an unresolved hierarchical triple system.[6]