(612911) 2004 XR190

(612911) 2004 XR190
Hubble Space Telescope image of 2004 XR190, taken in October 2010
Discovery
Discovered byCFEPS
Discovery siteMaunakea Obs.
Discovery date11 December 2004
Designations
"Buffy" (nickname)
Orbital characteristics(barycentric)
Epoch 2025 Ṃay 05 (JD 2460800.5)
Uncertainty parameter 2
Observation arc20.00 yr (8,036 d)
Earliest precovery date6 December 2002
Aphelion63.794 AU
Perihelion51.134 AU
57.464 AU
Eccentricity0.1102
435.6 yr (160,600 d)
277.234°
0° 0m 8.064s / day
Inclination46.7276°
252.387°
26 May 2114
±5 days
283.849°
Known satellites0
Physical characteristics
  • 600±170 km (occultation)
  • ≥560 km (occultation)
  • 502 km? (est.)
  • 335–530 km (est.)
  • 425–850 km (est.)
  • 350–784 km (est.)
  • 19.47 h (single-peaked)
  • 10.57 h (double-peaked)
  • 7.26 h (third-peaked)
  • 0.095±0.23 (R-band, occultation)
  • 0.04–0.16 (assumed)
  • 0.130 (assumed)
  • 0.10–0.25 (assumed)
  • 21.8±0.2 (r-band)
  • 21.9+0.8
    −1.5     (G-band)
  • 21.85±0.35 (wide-band)
  • 21.8+0.7
    −0.4     (several other bands)
  • 3.802±0.022 (R-band, 2022)
  • 3.937±0.036 (R-band, 2012)
  • 4.33
  • 4.32
  • 4.4
  • 4.47
  • 4.50

(612911) 2004 XR190, internally nicknamed Buffy by the discovery team, is a trans-Neptunian object, classified as both a scattered disc object and a detached object, located in the outermost region of the Solar System. It was first observed on 11 December 2004, by astronomers with the Canada–France Ecliptic Plane Survey at the Mauna Kea Observatories, Hawaii, United States.

2004 XR190 is one of the largest known highly inclined (> 45°) objects. With a perihelion of 51 AU, it belongs to a small and poorly understood group of very distant objects with moderate eccentricities.

Observation history

Discovery

The Canada–France–Hawaii Telescope, the telescope that discovered 2004 XR190 on 11 December 2004.

2004 XR190 was discovered on 11 December 2004. It was discovered by astronomers led by (Rhiannon) Lynne Allen of the University of British Columbia as part of the Canada–France Ecliptic Plane Survey (CFEPS) using the Canada–France–Hawaii Telescope (CFHT) near the ecliptic. The team included Brett Gladman, John Kavelaars, Jean-Marc Petit, Joel Parker and Phil Nicholson. In 2015, six precovery images from 2002 and 2003 were found in Sloan Digital Sky Survey data.

Occultations

On 22 January 2021, an occultation by 2004 XR190 occurred.

Provisional designation, numbering and nickname

The object was informally nicknamed "Buffy" by the discovery team, after the fictional vampire slayer Buffy Summers, and the team proposed several Inuit-based official names to the International Astronomical Union in 2005. The provisional designation of 2004 XR190 indicates its discovery date, the first letter represents the first half of December and the second letter and the numbers after it mean that it is the 4793rd object discovered during that half-month.

Orbit and classification

2004 XR190 is located in the "gap", a poorly understood region.

2004 XR190 orbits the Sun at a distance of 51.1–63.8 AU once every 435 years and 7 months (159,111 days; semi-major axis of 57.46 AU). Its orbit has a moderate eccentricity of 0.11 and a high inclination of 47° with respect to the ecliptic. It came to aphelion around 1901.

It belongs to the same group as (690420) 2014 FC72, 2014 FZ71, 2015 FJ345 and 2015 KQ174 (also see diagram), that are poorly understood for their large perihelia combined with moderate eccentricities. Considered a scattered and detached object, 2004 XR190 is particularly unusual as it has an unusually circular orbit for a scattered-disc object (SDO). Although it is thought that traditional scattered-disc objects have been ejected into their current orbits by gravitational interactions with Neptune, the low eccentricity of its orbit and the distance of its perihelion (SDOs generally have highly eccentric orbits and perihelia less than 38 AU) seems hard to reconcile with such celestial mechanics. This has led to some uncertainty as to the current theoretical understanding of the outer Solar System. The theories include close stellar passages, unseen planet/rogue planets/planetary embryos in the early Kuiper belt, and resonance interaction with an outward-migrating Neptune. The Kozai mechanism is capable of transferring orbital eccentricity to a higher inclination.

A conference abstract by Jones and others in 2006 shows that 2004 XR190 is not in a 8:3 mean motion resonance with Neptune.

The object is one of the largest objects with an inclination larger than 45°, traveling further "up and down" than "left to right" around the Sun when viewed edge-on along the ecliptic.

Physical characteristics

Diameter and shape

Older estimates used assumed albedos between 0.04 and 0.25, and absolute magnitudes from 4.3 to 4.6, 2004 XR190 had an estimated diameter of 335 to 850 kilometers; the mean arrived at by considering the two single-figure estimates plus the centre points of the three ranges is 562 km, approximately a quarter the diameter of Pluto. Johnston's archive estimates a diameter of 502 kilometers. However, a thesis by Flavia Luane Rommel, shows a stellar occultation observed by Westport Green Gao Westport in the USA and another one in Sant Esteve Sesrovires in Catalonia, Spain, which shows that it has longest dimension of 716 ± 132 kilometres (445 ± 82 mi), and an equivalent diameter of 600 ± 170 kilometres (370 ± 110 mi), with a oblateness of 0.32±0.14. Another website named "euraster.ericfrappa.com" yielded a diameter of at least 560 kilometres (350 mi) of the same occultation.

Surface and spectra

A study by Hainaut et al. shows that 2004 XR190 has color indices of: B-V of 0.790; V-R of 0.450; R-I of 0.520; and V-I of 0.970. with V-J, J-H and H-K having no known value. Another study by Peixinho et al. shows that 2004 XR190 has B-R of 1.240±0.040. An older study shows that it has color indices of: B-R of 1.24±0.04; V-R of 0.45±0.04; R-I of 0.52±0.04; and B-I of 1.76±0.04. Johnston's archive uses also a B-R of 1.24, and shows it is a BR object. A conference abstract by Jones and others in 2006 shows that it has color indices of: g'-r' of 0.55±0.04 and 0.30±0.04, making it in the "neutral or gray range of TNOs". 2004 XR190 has no known surface voaltiles. Johnston's archive also assumes an albedo of 0.130. A thesis by Flavia Luane Rommel, derives an albedo of 0.095±0.23, using the occultation model in the same thesis.

Rotation

A thesis by Flavia Luane Rommel, shows that there are many possibilities of the rotation period of 2004 XR190, with 19.47 hours (0.811 d) being the most likely rotation period, with only one peak. But there is also 10.57 hours (0.440 d) for the second peak, and 7.26 hours (0.303 d) for the third peak, although there still needs to be more observations to get an accurate value.

In the same thesis, they detect a lightcurve amplitude of 0.16 to 0.20 magnitudes, where 0.20 magnitudes is from the 19.47 hour rotation period, 0.17 for the 10.57 hour rotation period, and 0.16 for the 7.26 rotation period.

Notes

  1. 1 2 3 These orbital elements are expressed in terms of the Solar System Barycenter (SSB) as the frame of reference. Due to planetary perturbations, the Sun revolves around the SSB at non-negligible distances, so heliocentric-frame orbital elements and distances (such as those given in JPL's Small-Body Database) can vary on short timescales.
  2. ↑ Using AstDyS magnitude, Bruton formula, and commonly assumed minor planet albedo range of 0.05 to 0.25 (as detailed by Bruton)
  3. ↑ Reverse derived using Allen diameter and albedo data, and Bruton formula
  4. ↑ Reverse derived using Schaller diameter and albedo data, and Bruton formula
  5. ↑ The second letter 'R' indicates that it is the 18th object discovered on the 191st cycle of discoveries. Each completed cycle consists of 25 letters representing discoveries, hence 18 + (191 completed cycles × 25 letters) = 4793.

References

  1. 1 2 3 4 5 6 7 8 9 "2004 XR190". Minor Planet Center. Retrieved 13 December 2018.
  2. 1 2 3 "MPEC 2005-X72 : 2004 XR190". IAU Minor Planet Center. 12 December 2005. Retrieved 13 December 2018. (K04XJ0R)
  3. 1 2 Maggie McKee. "Strange new object found at edge of Solar System". New Scientist. Retrieved 13 December 2018.
  4. 1 2 3 4 "JPL Small-Body Database Browser: (2004 XR190)" (2024-12-06 last obs.). Jet Propulsion Laboratory. Retrieved 18 August 2025.
  5. 1 2 Jewitt, David, Morbidelli, Alessandro, & Rauer, Heike. (2007). Trans-Neptunian Objects and Comets: Saas-Fee Advanced Course 35. Swiss Society for Astrophysics and Astronomy. Berlin: Springer. ISBN 3-540-71957-1.
  6. 1 2 Lykawka, Patryk Sofia; Mukai, Tadashi (July 2007). "Dynamical classification of trans-neptunian objects: Probing their origin, evolution, and interrelation". Icarus. 189 (1): 213–232. Bibcode:2007Icar..189..213L. doi:10.1016/j.icarus.2007.01.001.
  7. 1 2 3 4 5 6 7 8 Johnston, Wm. Robert (19 January 2026). "List of Known Trans-Neptunian Objects". Johnston's Archive. Retrieved 13 December 2018.
  8. 1 2 3 4 "JPL/HORIZONS (612911) 2004 XR190 (Barycentric)". JPL Horizons On-Line Ephemeris System. Jet Propulsion Laboratory. Retrieved 21 October 2026. Solution using the Solar System Barycenter. Ephemeris Type: Elements and Center: @0)
  9. ↑ "JPL/HORIZONS (612911) 2004 XR190 (Heliocentric)". JPL Horizons On-Line Ephemeris System. Jet Propulsion Laboratory. Retrieved 21 October 2026. Solution using the Sun. Ephemeris Type: Elements and Center: @sun)
  10. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Rommel, Flavia Luane (19 December 2022). DETERMINATION OF PHYSICAL PROPERTIES AND TOPOGRAPHY OF TNOS FROM STELLAR OCCULTATIONS AND ROTATIONAL LIGHT CURVES: THE CASE OF 2002 MS4 OBJECT (PhD thesis). Rio de Janeiro: Observatório Nacional. Retrieved 26 September 2025.
  11. 1 2 Frappa, Eric (14 December 2022). "2021 European Asteroidal Occultation Results". euraster.net. Retrieved 18 October 2026.
  12. 1 2 3 4 5 Schaller, E. L.; Brown, M. E. (April 2007). "Volatile Loss and Retention on Kuiper Belt Objects" (PDF). The Astrophysical Journal. 659 (1): I.61 – I.64. Bibcode:2007ApJ...659L..61S. doi:10.1086/516709. S2CID 10782167. Retrieved 13 December 2018.
  13. 1 2 3 4 5 6 7 Allen, R. L.; Gladman, B.; Kavelaars, J. J.; Petit, J.-M.; Parker, J. W.; Nicholson, P. (March 2006). "Discovery of a Low-Eccentricity, High-Inclination Kuiper Belt Object at 58 AU". The Astrophysical Journal. 640 (1): L83–L86. arXiv:astro-ph/0512430. Bibcode:2006ApJ...640L..83A. doi:10.1086/503098. S2CID 15588453. (Discovery paper)
  14. 1 2 3 "2004 XR190". AstDyS-2, Asteroids Dynamic Site. Retrieved 18 August 2019.
  15. 1 2 3 4 Dan Bruton. "Conversion of Absolute Magnitude to Diameter for Minor Planets". Stephen F. Austin State University, College of Sciences and Mathematics, Department of Physics, Engineering and Astronomy. Archived from the original on 23 July 2011. Retrieved 15 August 2019.
  16. 1 2 Peixinho, N.; Delsanti, A.; Guilbert-Lepoutre, A.; Gafeira, R.; Lacerda, P. (2012). "The bimodal colors of Centaurs and small Kuiper belt objects" (PDF). Astronomy & Astrophysics. 546: A86. doi:10.1051/0004-6361/201219057. ISSN 0004-6361. Retrieved 18 October 2026.
  17. 1 2 "How Are Minor Planets Named?". Minor Planet Center. Retrieved 18 October 2026.
  18. ↑ "Horizon Online Ephemeris System". California Institute of Technology, Jet Propulsion Laboratory. Retrieved 23 March 2009.
  19. 1 2 R. L., Jones; B., Gladman; J., Kavelaars; J., Petit; J. W., Parker; P., Nicholson (September 2006). "The Unusual TNO 2004 XR190 (aka "Buffy")". American Astronomical Society. 38: 550. Bibcode:2006DPS....38.3703J.
  20. ↑ "JPL Small-Body Database Search Engine: H < 6.5 (mag)". JPL Solar System Dynamics. Retrieved 27 March 2014.
  21. ↑ Hainaut, O. R.; Boehnhardt, H.; Protopapa, S. (2012). "Colours of minor bodies in the outer solar system" (PDF). Astronomy & Astrophysics. 546: A115. doi:10.1051/0004-6361/201219566. ISSN 0004-6361. Retrieved 18 October 2026.
  22. ↑ Sheppard, Scott S. (4 March 2010). "The Colors of Extreme Outer Solar System Objects". The Astronomical Journal. 139 (4): 1394–1405. arXiv:1001.3674. Bibcode:2010AJ....139.1394S. doi:10.1088/0004-6256/139/4/1394.