(524366) 2001 XR254

(524366) 2001 XR₂₅₄
	Hubble Space Telescope image of 2001 XR254 and its satellite, taken in 2007.
Discovery
Discovered by	D. C. Jewitt; S. S. Sheppard; J. Kleyna
Discovery site	Mauna Kea Obs.
Discovery date	10 December 2001
Designations
MPC designation	(524366) 2001 XR254
Alternative designations	2001 XR254
Minor planet category	TNO · cubewano; cold
Orbital characteristics
	Epoch 27 April 2019 (JD 2458600.5)
	Uncertainty parameter 4 · 3
Observation arc	14.26 yr (5,207 d)
Aphelion	44.374 AU
Perihelion	41.178 AU
Semi-major axis	42.776 AU
Eccentricity	0.0374
Orbital period (sidereal)	279.78 yr (102,188 d)
Mean anomaly	226.02°
Mean motion	0° 0m 12.6s / day
Inclination	1.2309°
Longitude of ascending node	180.01°
Time of perihelion	≈ 7 September 2120; ±1 month
Argument of perihelion	78.868°
Known satellites	1 (D: 140 km; P: 125.58 d)
Physical characteristics
Mean diameter	221+41; −71 km (combined); 171+32; −55 km (primary)
Mass	(4.055±0.048)×1018 kg
Mean density	1.00+0.96; −0.56 g/cm3
Geometric albedo	0.136+0.168; −0.044
Spectral type	V−I = 1.06±0.12
Absolute magnitude (H)	5.7; 6.05

(524366) 2001 XR₂₅₄, provisional designation 2001 XR₂₅₄, is a trans-Neptunian object and binary system from the classical Kuiper belt, located in the outermost region of the Solar System. The cubewano belongs to the cold population and measures approximately 171 kilometers (110 miles).^[8] It was first observed on 10 December 2001, by astronomers at the Mauna Kea Observatory, Hawaii. Its 140-kilometer sized companion was discovered by the Hubble Space Telescope in June 2006.^[7]

Discovery and orbit

2001 XR₂₅₄ was discovered on 10 December 2001 by David C. Jewitt, Scott S. Sheppard and Jan Kleyna using 2.2-meter University of Hawaii reflector on Mauna Kea.^[2] 2001 XR₂₅₄ belongs to the dynamically cold population of the classical Kuiper belt objects, with small orbital eccentricities and inclinations. Their semi-major axes reside mainly in the interval 40–45 AU.^[8]

Satellite

2001 XR₂₅₄ is a binary consisting of two components of approximately equal size. Assuming that both components have the same albedo, the primary is estimated to be about 170 km in diameter. The size of the secondary (satellite) in this case is estimated at about 140 km. The total mass of the system is about 4×10¹⁸ kg. The average density of both components is about 1 g/cm³.^[8]

Orbital parameters of the 2001 XR₂₅₄ system^[9]
Semi-major axis (km)	Eccentricity	Period (d)	Inclination (°)
9311 ± 52	0.5561 ± 0.0047	125.579 ± 0.048	41.08 ± 0.22

Numbering and naming

This minor planet was numbered by the Minor Planet Center on 18 May 2019 (M.P.C. 114619). As of 2025, it has not been named.^[10]

Physical properties

The surfaces of both components of 2001 XR₂₅₄ appear to have a neutral color.^[8]

Notes

^ Assuming that both components have equal albedos and equal densities

References

^ ^a ^b ^c "2001 XR254". Minor Planet Center. Retrieved 3 December 2018.
^ ^a ^b ^c Marsden, Brian G. (1 November 2002). "MPEC 2002-V07 : 2001 XR254, 2001 XS254, 2001 XU254". IAU Minor Planet Center. Harvard-Smithsonian Center for Astrophysics. Retrieved 3 December 2018.
^ ^a ^b ^c "JPL Small-Body Database Browser: (2001 XR254)" (2016-03-13 last obs.). Jet Propulsion Laboratory. Retrieved 3 December 2018.
^ Marc W. Buie. "Orbit Fit and Astrometric record for 01XR254". SwRI (Space Science Department). Retrieved 17 February 2018.
^ Brown, Michael E. "How many dwarf planets are there in the outer solar system?". California Institute of Technology. Retrieved 3 December 2018.
^ JPL Horizons Observer Location: @sun (Perihelion occurs when deldot changes from negative to positive. Uncertainty in time of perihelion is 3-sigma.)
^ ^a ^b ^c Johnston, Wm. Robert (23 June 2015). "Asteroids with Satellites Database – 2001 XR254". Johnston's Archive. Retrieved 3 December 2018.
^ ^a ^b ^c ^d ^e ^f ^g ^h Vilenius, E.; Kiss, C.; Mommert, M.; Müller, T.; Santos-Sanz, P.; Pal, A.; et al. (May 2012). ""TNOs are Cool": A survey of the trans-Neptunian region. VI. Herschel/PACS observations and thermal modeling of 19 classical Kuiper belt objects". Astronomy and Astrophysics. 541: 17. arXiv:1204.0697. Bibcode:2012A&A...541A..94V. doi:10.1051/0004-6361/201118743. S2CID 54222700.
^ ^a ^b Grundy, W.M.; Noll, K.S.; Roe, H.G.; Buie, M.W.; Porter, S.B.; Parker, A.H.; Nesvorný, D.; Levison, H.F.; Benecchi, S.D.; Stephens, D.C.; Trujillo, C.A. (December 2019). "Mutual orbit orientations of transneptunian binaries". Icarus. 334: 62–78. doi:10.1016/j.icarus.2019.03.035.
^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 29 May 2019.

External links

List of Transneptunian Objects, Minor Planet Center
List of binary asteroids/TNOs, Johnston's Archive
(524366) 2001 XR254 at AstDyS-2, Asteroids—Dynamic Site
- Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
(524366) 2001 XR254 at the JPL Small-Body Database
- Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters

[equal-10] Assuming that both components have equal albedos and equal densities

[MPC-object-1] "2001 XR254". Minor Planet Center. Retrieved 3 December 2018.

[MPEC2002-V07-2] Marsden, Brian G. (1 November 2002). "MPEC 2002-V07 : 2001 XR254, 2001 XS254, 2001 XU254". IAU Minor Planet Center. Harvard-Smithsonian Center for Astrophysics. Retrieved 3 December 2018.

[jpldata-3] "JPL Small-Body Database Browser: (2001 XR254)" (2016-03-13 last obs.). Jet Propulsion Laboratory. Retrieved 3 December 2018.

[Buie-4] Marc W. Buie. "Orbit Fit and Astrometric record for 01XR254". SwRI (Space Science Department). Retrieved 17 February 2018.

[Brown-dplist-5] Brown, Michael E. "How many dwarf planets are there in the outer solar system?". California Institute of Technology. Retrieved 3 December 2018.

[perihelion-6] JPL Horizons Observer Location: @sun (Perihelion occurs when deldot changes from negative to positive. Uncertainty in time of perihelion is 3-sigma.)

[johnstonsarchive-BIN-7] Johnston, Wm. Robert (23 June 2015). "Asteroids with Satellites Database – 2001 XR254". Johnston's Archive. Retrieved 3 December 2018.

[TNOsCool-10-8] ^ ^a ^b ^c ^d ^e ^f ^g ^h Vilenius, E.; Kiss, C.; Mommert, M.; Müller, T.; Santos-Sanz, P.; Pal, A.; et al. (May 2012). ""TNOs are Cool": A survey of the trans-Neptunian region. VI. Herschel/PACS observations and thermal modeling of 19 classical Kuiper belt objects". Astronomy and Astrophysics. 541: 17. arXiv:1204.0697. Bibcode:2012A&A...541A..94V. doi:10.1051/0004-6361/201118743. S2CID 54222700.

[Grundy2019-9] Grundy, W.M.; Noll, K.S.; Roe, H.G.; Buie, M.W.; Porter, S.B.; Parker, A.H.; Nesvorný, D.; Levison, H.F.; Benecchi, S.D.; Stephens, D.C.; Trujillo, C.A. (December 2019). "Mutual orbit orientations of transneptunian binaries". Icarus. 334: 62–78. doi:10.1016/j.icarus.2019.03.035.

[MPC-Circulars-Archive-11] "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 29 May 2019.

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v t e Trans-Neptunian objects
TNO classes	Classical Kuiper belt objects Scattered-disc objects Detached objects Resonant objects Neptune trojans plutinos twotinos TNO moons
Dwarf planets (moons)	Orcus Vanth Pluto Charon Styx Nix Kerberos Hydra Haumea Namaka Hiʻiaka ring Quaoar Weywot rings Makemake MK2 Gonggong Xiangliu Eris Dysnomia Sedna
Sednoids	Sedna 2012 VP113 'Biden' Leleākūhonua 2023 KQ14 'Ammonite'

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Discovery^[1]^[2]
Hubble Space Telescope image of 2001 XR₂₅₄ and its satellite, taken in 2007.
Discovered by	D. C. Jewitt S. S. Sheppard J. Kleyna
Discovery site	Mauna Kea Obs.
Discovery date	10 December 2001
Designations
MPC designation	(524366) 2001 XR₂₅₄
Alternative designations	2001 XR₂₅₄
Minor planet category	TNO^[3] · cubewano^[4]^[2] cold^[5]
Orbital characteristics^[3]
Epoch 27 April 2019 (JD 2458600.5)
Uncertainty parameter 4 · 3^[1]
Observation arc	14.26 yr (5,207 d)
Aphelion	44.374 AU
Perihelion	41.178 AU
Semi-major axis	42.776 AU
Eccentricity	0.0374
Orbital period (sidereal)	279.78 yr (102,188 d)
Mean anomaly	226.02°
Mean motion	0° 0^m 12.6^s / day
Inclination	1.2309°
Longitude of ascending node	180.01°
Time of perihelion	≈ 7 September 2120^[6] ±1 month
Argument of perihelion	78.868°
Known satellites	1 (D: 140 km; P: 125.58 d)^[7]^[8]
Physical characteristics
Mean diameter	221+41 −71 km (combined) 171+32 −55 km (primary)
Mass	(4.055±0.048)×10¹⁸ kg^[9]
Mean density	1.00+0.96 −0.56 g/cm³^[8]^[a]
Geometric albedo	0.136+0.168 −0.044^[8]
Spectral type	V−I = 1.06±0.12^[7]
Absolute magnitude (H)	5.7^[1]^[3] 6.05^[8]