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]
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]
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]
^Nelsen, Maia A.; Ragozzine, Darin; Proudfoot, Benjamin C. N.; Giforos, William G.; Grundy, Will (2024-03-19). "Beyond Point Masses. IV. TNO Altjira is Likely a Hierarchical Triple Discovered Through Non-Keplerian Motion". arXiv:2403.12786 [astro-ph.EP].