148780 Altjira

Binary Kuiper belt object yes #C2E0FF (148780) Altjira 148780-altjira-hubble.jpg Altjira and its companion imaged by the Hubble Space Telescope in 2006 Deep Ecliptic Survey at Kitt Peak 20 October 2001 (148780) Altjira 2001 UQ 18 æ l ˈ tʃ ɪər ə Altjira Classical KBO (DES)Marc W. Buie Marc W. Buie Orbit Fit and Astrometric record for 148780 SwRI (Space Science Department) https://www.boulder.swri.edu/~buie/kbo/astrom/148780.html 2011-11-29 2022-11-28 last obs JPL Small-Body Database Browser: 148780 Altjira (2001 UQ18) https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=148780 2025-08-26 2025 May 05 (JD 2460800.5) 7,709 days (21.11 yr) 4 44.55 AU Tm on 42.00 AU Tm on 47.11 AU Tm on on 0.0573 297.40 yr (108626 31 d) 1919 Feb 16 ±37 days 5.198° 1.84° 304° 129° 0.003314°/day 1 confirmed, 1 suspected 331 51 187 km (combined) 246 38 139 km (primary) 3.952 0.067 18 kg (system) 2.338 18 kg (primary)Assuming a spherical diameter of 246 km and a density of 0.3 g/cm3 0.30 0.50 0.14 g/cm3 B−V = 0.91 0.13 V−R = 0.74 0.08 V−I = 1.17 0.09 5.77; 5.4 (system), 5.1 (primary) 0.0430 0.1825 0.0095 148780 Altjira (provisional designation 2001 UQ 18) appears to be a triple or contact binary double classical Kuiper belt object.Johnston's Archive on (148780) Altjira Retrieved 2011-11-29 The secondary is large compared to the primary, approximately 246 km mi of the primary vs. 221 km mi to the secondary. The lightcurve is quite flat (Δmag < 0.10), which is indicative of a "quasi-spherical body with a homogeneous surface".0910.1472 10.1051/0004-6361/200912601 Transneptunian objects and Centaurs from light curves 2009 Duffard R. Ortiz J. L. Thirouin A. Santos-Sanz P. Morales N. Astronomy & Astrophysics 505 3 1283–1295 2009A&A...505.1283D The system mass is 4 18 kg. Grundy W. M. Noll K. S. Nimmo F. Roe H. G. Buie M. W. Porter S. B. Benecchi S. D. Stephens D. C. Levison H. F. 10.1016/j.icarus.2011.03.012 Stansberry J. A. Five new and three improved mutual orbits of transneptunian binaries Icarus 213 2 678 2011 2011Icar..213..678G 1103.2751 9571163 In 2008, Altjira was named after the Arrernte creation deity, Altjira (Alchera). Physical characteristics Altjira is a binary system consisting of two bodies of nearly equal size, making it a true synchronous binary rather than a typical primary-satellite system. Size and dimensions Observations using thermal modeling indicate that the Altjira system has a combined effective diameter of approximately 331 51 187 km. The primary body has an estimated diameter of 246 (+38/−139) km, while the secondary body (the companion) possesses a radius of roughly 111 km (a diameter of ~222 km). Density and porosity The bulk density of Altjira is exceptionally low, estimated at roughly 0.3 0.50 0.14 g/cm3 (300 kg/m3). This makes Altjira one of the least dense known large Kuiper belt objects (KBOs). Such an incredibly low density implies that the interiors of both bodies are highly porous, resembling loose "rubble piles" rather than solid ice or rock. Albedo and color Altjira has a relatively high geometric albedo, measured at 0.14 0.05. It exhibits a very red surface color in the visible spectrum, which is a typical trait among cold classical Kuiper belt objects. Satellite Satellite of Altjira 6 August 2006 9904 56 km 0.3445 0.0045 139.561 0.047 d 35.19 0.19 ° (retrograde) 148780 Altjira 221 34 125 km 1.695 18 kgAssuming a spherical diameter of 221 km and a density identical to the primary difference from primary: 0.7 ±0.2 Altjira's companion was discovered on 6 August 2006, from images taken by the Hubble Space Telescope. The companion has no official designation.designation Nelsen et al. (2025) claim that Altjira's companion is designated "S/2007 (148780) 1", even though it was discovered in 2006. The JPL Small Body Database and Johnstons Archive do not recognize any official designation for the companion. The secondary'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). There is indirect evidence that Altjira may be an unresolved hierarchical triple system. See also 47171 Lempo – the first and only confirmed hierarchical triple system in the Kuiper belt 58534 Logos – a contact binary and potential triple system in the cold classical Kuiper belt Notes References "TNOs are Cool": A survey of the trans-Neptunian region X. Analysis of classical Kuiper belt objects from Herschel and Spitzer observations Vilenius E. Kiss C. Mommert M. 2014 Astronomy & Astrophysics A35 564 10.1051/0004-6361/201322416 1403.6309 etal 2014A&A...564A..35V 118513049 The Meudon Multicolor Survey (2MS) of Centaurs and trans-neptunian objects: extended dataset and status on the correlations reported Doressoundiram A. Peixinho N. Doucet C. Mousis O. Barucci M. A. Petit J. M. Veillet C. 2005 Icarus 174 1 90–104 10.1016/j.icarus.2004.09.009 2005Icar..174...90D 122936619 Nelsen Maia A. Beyond Point Masses. IV. TNO Altjira is Likely a Hierarchical Triple Discovered Through Non-Keplerian Motion March 2025 The Planetary Science Journal 6 3 53 10.3847/PSJ/ad864d 2403.12786 Ragozzine Darin Proudfoot Benjamin C. N. Giforos William G. Grundy Will free Wm. Robert Johnston (148780) Altjira https://www.johnstonsarchive.net/astro/astmoons/am-148780.html Johnston's Archive 2014-09-20 2026-08-05 External links 148780 (148779) 2001 UJ18 148780 (148781) 2001 UL19 148780 148780 Category:Named minor planets Category:Binary trans-Neptunian objects 20011020 Category:Triple trans-Neptunian objects Category:Contact binary (small Solar System body) Category:Named TNOs