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148780 Altjira

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Binary Kuiper belt object

(148780) Altjira
Discovery
Altjira and its companion imaged by theHubble Space Telescope in 2006
Discovery site	Deep Ecliptic Survey atKitt Peak^[1]
Discovery date	20 October 2001
Designations
MPC designation	(148780) Altjira
Pronunciation	/ælˈtʃɪərə/
Named after	Altjira
Alternative designations	2001 UQ₁₈
Minor planet category	Classical KBO (DES)^[2]
Orbital characteristics^[1]
Epoch 2025 May 05 (JD 2460800.5)
Uncertainty parameter 4
Observation arc	7,709 days (21.11 yr)
Aphelion	47.11 AU (7.048 Tm)
Perihelion	42.00 AU (6.283 Tm)
Semi-major axis	44.55 AU (6.665 Tm)
Eccentricity	0.0573
Orbital period (sidereal)	297.40yr (108626±31d)
Mean anomaly	129°
Mean motion	0.003314°/day
Inclination	5.198°
Longitude of ascending node	1.84°
Time of perihelion	1919 Feb 16±37 days
Argument of perihelion	304°
Knownsatellites	1 confirmed, 1 suspected
Physical characteristics
Mean diameter	331+51 −187 km (combined) 246+38 −139 km (primary)^[3]
Mass	(3.952±0.067)×10¹⁸ kg (system)^[4]
Meandensity	0.30+0.50 −0.14 g/cm³^[3]
Geometric albedo	0.0430+0.1825 −0.0095^[3]
Spectral type	B−V =0.91±0.13 V−R =0.74±0.08 V−I =1.17±0.09^[5]
Absolute magnitude (H)	5.77;^[1] 5.4 (system), 5.1 (primary)^[6]

Satellite
Discovery
Discovery date	6 August 2006^[6]
Orbital characteristics^[4]
Semi-major axis	9904±56 km
Eccentricity	0.3445±0.0045
Orbital period (sidereal)	139.561±0.047 d
Inclination	35.19°±0.19° (retrograde)
Satellite of	148780 Altjira
Physical characteristics
Mean diameter	221+34 −125 km^[3]
Absolute magnitude (H)	difference from primary:0.7±0.2^[6]

148780 Altjira (provisional designation2001 UQ₁₈) appears to be a triple or contact binary doubleclassical Kuiper belt object.^[6] The secondary is large compared to the primary, approximately 246 kilometres (153 mi) vs. 221 kilometres (137 mi).^[3] The lightcurve is quite flat (Δmag < 0.10), which is indicative of a "quasi-spherical body with ahomogeneous surface".^[7]The system mass is4×10¹⁸ kg.^[4]

Itscompanion was discovered on 6 August 2006, from images taken by theHubble Space Telescope.^[8] The secondary's orbit has the following parameters: semi-major-axis,9904±56 km; period,139.561±0.047 d; eccentricity,0.3445±0.0045; and inclination,35.19°±0.19° (retrograde). There is indirect evidence that Altjira may be an unresolvedhierarchical triple system.^[9]

In 2008, Altjira was named after theArrernte creation deity,Altjira (Alchera).^[1]

References

[edit]

^^a ^b ^c ^d"JPL Small-Body Database Browser: 148780 Altjira (2001 UQ18)" (2022-11-28 last obs). Retrieved2025-08-26.
^Marc W. Buie."Orbit Fit and Astrometric record for 148780". SwRI (Space Science Department). Retrieved2011-11-29.
^^a ^b ^c ^d ^eVilenius, E.; Kiss, C.; Mommert, M.; et al. (2014). ""TNOs are Cool": A survey of the trans-Neptunian region X. Analysis of classical Kuiper belt objects from Herschel and Spitzer observations".Astronomy & Astrophysics.564: A35.arXiv:1403.6309.Bibcode:2014A&A...564A..35V.doi:10.1051/0004-6361/201322416.S2CID 118513049.
^^a ^b ^cGrundy, 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.; Stansberry, J. A. (2011). "Five new and three improved mutual orbits of transneptunian binaries".Icarus.213 (2): 678.arXiv:1103.2751.Bibcode:2011Icar..213..678G.doi:10.1016/j.icarus.2011.03.012.S2CID 9571163.
^Doressoundiram, A.; Peixinho, N.; Doucet, C.; Mousis, O.; Barucci, M. A.; Petit, J. M.; Veillet, C. (2005). "The Meudon Multicolor Survey (2MS) of Centaurs and trans-neptunian objects: extended dataset and status on the correlations reported".Icarus.174 (1):90–104.Bibcode:2005Icar..174...90D.doi:10.1016/j.icarus.2004.09.009.S2CID 122936619.
^^a ^b ^c ^dJohnston's Archive on (148780) Altjira Retrieved 2011-11-29
^Duffard, R.; Ortiz, J. L.; Thirouin, A.; Santos-Sanz, P.; Morales, N. (2009). "Transneptunian objects and Centaurs from light curves".Astronomy & Astrophysics.505 (3):1283–1295.arXiv:0910.1472.Bibcode:2009A&A...505.1283D.doi:10.1051/0004-6361/200912601.
^"(148780) Altjira = 2001 UQ18".minorplanetcenter.net. Retrieved2025-09-03.
^Nelsen, Maia A.; Ragozzine, Darin; Proudfoot, Benjamin C. N.; Giforos, William G.; Grundy, Will (March 2025)."Beyond Point Masses. IV. TNO Altjira is Likely a Hierarchical Triple Discovered Through Non-Keplerian Motion".The Planetary Science Journal.6 (3): 53.arXiv:2403.12786.doi:10.3847/PSJ/ad864d.

External links

[edit]

148780 Altjira at theJPL Small-Body Database
- Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters

v t e Minor planets navigator
(148779) 2001 UJ18 148780 Altjira (148781) 2001 UL19

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