145451 Rumina

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145451 Rumina
Rumina imaged by the Hubble Space Telescope on 2 November 2008
Discovery[1]
Discovered byA. C. Becker
A. W. Puckett
J. M. Kubica
Discovery siteApache Point Obs.
Discovery date9 September 2005
Designations
Pronunciation/ruːˈmaɪnə/
Named after
Rumīna
2005 RM43
SDO[2] · TNO[1]
Orbital characteristics[1]
Epoch 2025 May 05 (JD 2460800.5)
Uncertainty parameter 1
Observation arc48.18 yr (17,596 d)
Earliest precovery date17 November 1976
Aphelion149.67 AU (22.390 Tm)
Perihelion35.147 AU (5.2579 Tm)
92.41 AU (13.824 Tm)
Eccentricity0.6197
888.36 yr (324475±19 d)
8.226°
0° 0m 3.994s / day
Inclination28.6976°
84.629°
318.672°
Known satellites0
Physical characteristics
≈644 km (derived from occultation; 455 and 460 km measured)[3]
524+96
−103 km[4]
Mean density
>0.15 g/cm3[5]
0.48–0.63 g/cm3 (assuming a Jacobi ellipsoid)[5]
6.71 h (0.280 d)[1]
9.00 h (0.375 d)[5]
0.102[4]
V–R=0.33±0.02 (neutral)[4]
B0−V0=0.590[6]
B–R=0.99[2]
20.4[7]
4.52±0.01[4]
4.4[1] · 4.8[8]

145451 Rumina (provisional designation 2005 RM43) is a large trans-Neptunian object in the scattered disc region beyond the Kuiper belt. It was discovered on 9 September 2005, by American astronomers Andrew Becker, Andrew Puckett and Jeremy Kubica at Apache Point Observatory in Sunspot, New Mexico.

It measures approximately 600 kilometers in diameter, and has an albedo of ~0.102,[4] with a grey colored surface.[4]

History

Discovery

The 2.5-meter telescope at Apache Point Observatory in Sunspot that was used to discover Rumina back in 2005

Rumina was discovered by astronomers Andrew Becker, Andrew Puckett and Jeremy Kubica on 9 September 2005, during observations for the Sloan Digital Sky Survey.[9][10] The discovery observations were made using the 2.5-meter telescope at Apache Point Observatory in Sunspot, New Mexico.[10] The discoverers further observed Rumina until November 2005 and found the object in precovery observations from dates as early as October 1999.[10] The discovery of Rumina was announced by the Minor Planet Center on 23 July 2006.[10] Since then, Rumina has been found in even earlier precovery observations dating back to November 1976.[9] Rumina has been observed 548 times, the orbit is well determined with an uncertainty parameter of 1.[1]

Naming and numbering

The object is named after Rumīna, a Roman goddess who protected nursing mothers.[11]: 7  The naming of this object was announced by the International Astronomical Union's Working Group for Small Body Nomenclature on 1 September 2025.[11]: 24  Before Rumina was officially named, it was known by its provisional designation 2005 RM43,[9] which indicates the year and half-month of the object's discovery date.[12] Rumina's minor planet catalog number of 145451 was given by the Minor Planet Center on 5 December 2006.[13] The Kuiper belt objects 145452 Ritona and (145453) 2005 RR43 directly come after Rumina's number in the minor planet catalog.[13]

Orbit and classification

Orbital characteristics

Rumina orbits the Sun at a distance of 35.1–149.7 astronomical units (AU) with a semi-major axis or average orbital distance of 92.4 AU once every 888 years (for reference, Neptune's orbit is at 30 AU).[1][14]

Its orbit has a relatively high eccentricity of 0.62 and an inclination of 28.7° with respect to the ecliptic.[1]

Classification

Rumina belongs to the scattered disc,[2] which is a population of TNOs that have distant, inclined, and eccentric orbits that come close to Neptune at perihelion.

The scattered disc population, which includes the dwarf planets Eris and Gonggong, are strongly influenced by Neptune's gravitational perturbations and consequently experience gravitational scattering.[15]: 52 

Both the Minor Planet Center (MPC) and Johnston's archive classify that Rumina is a scattered disc object.[2][16]

Physical characteristics

Size

In 2018, two stellar occultations by Rumina were observed on 3 February and 24 December.[3] The February occultation yielded a single chord length of 456 km (283 mi).[17] Observations of the December occultation yielded two positive chords, which together suggest an approximate diameter of 644 km (400 mi).[18] The object rotates on its axis once every 6.71 hours.[1]

Density, shape, and rotation

Based on its size of 456 and 644 km,[17][18] it belongs to the proposed class of "mid-sized" TNOs between 400 and 1,000 km (250 and 620 mi) in diameter, which are believed to represent the transition between small, low-density TNOs and large, high-density dwarf planets.[19][20]: 1  Planetary scientists have hypothesized that mid-sized TNOs should have highly porous and unheated interiors, because TNOs in this size range (namely Uni and Gǃkúnǁʼhòmdímà) have been found to have low densities around 1 g/cm3.[19] Johnston's archive estimate a density of >0.56 g/cm3 for Rumina.[2]

The density and shape of Rumina have been calculated by studying its rotational light curve. Photometric observations show that Rumina has a synodic rotational period of 9.00±0.06 h and a light curve amplitude of 0.12±0.05 mag.[5] This light variation indicates a primary axis ratio lower limit of 1.12±0.05.[5]

Based on these rotational mechanics, the absolute minimum density required to keep the object from breaking apart due to centrifugal forces is 0.15 g/cm3.[5] If Rumina is assumed to be a rotationally stable Jacobi ellipsoid in hydrostatic equilibrium, its bulk density is modeled to be within the range of 0.48–0.63 g/cm3,[5] which is probably too low to be solid.

Surface and spectra

Rumina has an absolute magnitude of 4.52±0.01.[4] The surface of Rumina is dark grey with a low albedo of 0.102 and a V–R color index of 0.33±0.02, which means that it has a neutral color.[4]

See also

References

  1. "JPL Small-Body Database Browser: 145451 Rumina (2005 RM43)" (2025-01-20 last obs). Retrieved August 19, 2025.
  2. Wm. Robert Johnston. "List of Known Trans-Neptunian Objects". Johnston's Archive. Archived from the original on 2 February 2019. Retrieved 2 February 2019.
  3. "TNO Results". ERC Lucky Star Project. Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique (LESIA). Retrieved 13 July 2020.
  4. Farkas-Takács, A.; Kiss, Cs.; Vilenius, E.; Marton, G.; Müller, T. G.; Mommert, M.; et al. (28 February 2020). "TNOs are Cool! A Survey of the transneptunian Region XV. Physical characteristics of 23 resonant transneptunian and scattered disk objects". Astronomy & Astrophysics. A23: 638. arXiv:2002.12712. Bibcode:2020A&A...638A..23F. doi:10.1051/0004-6361/201936183. S2CID 216193564.
  5. Perna, D.; Dotto, E.; Barucci, M. A.; Rossi, A.; Fornasier, S.; de Bergh, C. (2009). "Rotations and densities of trans-Neptunian objects (Research Note)" (PDF). Astronomy & Astrophysics. 508 (1): 451–455. doi:10.1051/0004-6361/200911970.
  6. David L. Rabinowitz; Bradley E. Schaefer; Martha W. Schaefer; Suzanne W. Tourtellotte (2008). "The Youthful Appearance of the 2003 EL61 Collisional Family". The Astronomical Journal. 136 (4): 1502–1509. arXiv:0804.2864. Bibcode:2008AJ....136.1502R. doi:10.1088/0004-6256/136/4/1502. S2CID 117167835.
  7. AstDyS. "(145451) 2005RM43 – Observation prediction". Department of Mathematics, University of Pisa. Retrieved 2 February 2019.
  8. Michael E. Brown. "How many dwarf planets are there in the outer solar system? (updates daily)". California Institute of Technology. Archived from the original on 2 February 2019. Retrieved 2 February 2019.
  9. "(145451) Rumina = 2005 RM43". Minor Planet Center. Retrieved 2 February 2019.
  10. Becker, A. C.; Puckett, A. W.; Kubika, J.; Williams, G. V. (2006-07-23). "MPEC 2006-O24 : 2005 RM43". Minor Planet Electronic Circular. 2006-O25. Minor Planet Center. Bibcode:2006MPEC....O...24B. Retrieved 2025-09-01.
  11. "(145451) Rumina = 2005 RM43" (PDF). WGSBN Bulletin. 5 (20). International Astronomical Union: 7. Rumina is a minor Roman goddess who was invoked as a protector of nursing mothers.
  12. "New- And Old-Style Minor Planet Designations". Minor Planet Center. Retrieved 2025-09-01.
  13. "M.P.C. 58206" (PDF). Minor Planet Circulars (58206). Minor Planet Center: 160. 2006-12-05. Retrieved 2025-09-01.
  14. Yeomans, Donald K. "HORIZONS Web-Interface for Neptune Barycenter (Major Body=8)". JPL Horizons On-Line Ephemeris System. Archived from the original on 7 September 2021. Retrieved 18 July 2014.—Select "Ephemeris Type: Orbital Elements", "Time Span: 2000-01-01 12:00 to 2000-01-02". ("Target Body: Neptune Barycenter" and "Center: Solar System Barycenter (@0)".)
  15. Gladman, Brett; Marsden, Brian G.; VanLaerhoven, Christa (2008). "Nomenclature in the Outer Solar System" (PDF). The Solar System Beyond Neptune. University of Arizona Press. pp. 43–57. arXiv:astro-ph/0702538. Bibcode:2008ssbn.book...43G. ISBN 9780816527557. S2CID 14469199. Archived from the original (PDF) on 1 August 2023.
  16. "List Of Centaurs and Scattered-Disk Objects". Minor Planet Center. International Astronomical Union. Retrieved 17 December 2021.
  17. "Occultation by 2005 RM43 in 03 02 2018" (PDF). ERC Lucky Star Project. Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique (LESIA). 3 February 2018. Retrieved 13 July 2020.
  18. "Occultation by 2005 RM43 in 23 DEC 2018" (PDF). ERC Lucky Star Project. Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique (LESIA). 24 December 2018. Retrieved 13 July 2020.
  19. Grundy, W. M.; Noll, K. S.; Buie, M. W.; Benecchi, S. D.; Ragozzine, D.; Roe, H. G. (December 2019). "The Mutual Orbit, Mass, and Density of Transneptunian Binary Gǃkúnǁʼhòmdímà ((229762) 2007 UK126)" (PDF). Icarus. 334: 30–38. Bibcode:2019Icar..334...30G. doi:10.1016/j.icarus.2018.12.037. S2CID 126574999. Archived from the original (PDF) on 2019-04-07. Retrieved 2026-03-30.
  20. Sheppard, Scott; Fernandez, Yanga; Moullet, Arielle (6 September 2018). "The Albedos, Sizes, Colors and Satellites of Dwarf Planets Compared with Newly Measured Dwarf Planet 2013 FY27". The Astronomical Journal. 156 (6): 270. arXiv:1809.02184. Bibcode:2018AJ....156..270S. doi:10.3847/1538-3881/aae92a. S2CID 119522310.