145452 Ritona

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145452 Ritona
Ritona Hubble 2010 north-up.png
Ritona imaged by the Hubble Space Telescope on 25 April 2010
Discovery [1]
Discovered by
Discovery site Apache Point Obs.
Discovery date10 September 2005
Designations
(145452) Ritona
Pronunciation /ˈrɪtənə/
Named after
 Ritona
2005 RN43
Orbital characteristics   (barycentric) [5]
Epoch 5 May 2025 (JD 2460800.5)
Uncertainty parameter 0 [2]
Observation arc 70.99 yr (25930 days)
Earliest precovery date2 June 1954
Aphelion 42.450 AU
Perihelion 40.575
41.512 AU
Eccentricity 0.0226
267.29  yr (97,627  d)
352.812°
0° 0m 13.275s / day
Inclination 19.274°
186.989°
≈ 15 June 2029 [6]
172.899°
Known satellites 0
Physical characteristics
679+55
−73 km [3]
0.107+0.029
−0.018 [3]
Temperature 43.2  K (perihelion) [8] : 11 
≈ 20 (average) [1] [11] : 5 
  • 3.882±0.036 (2016) [12] : 14 
  • 3.89±0.05 (2012) [3] : 3 
  • 3.69 (JPL) [2]

    145452 Ritona (provisional designation 2005 RN43) is a large trans-Neptunian planetoid orbiting the Sun in the Kuiper belt. It was discovered on 10 September 2005 by astronomers Andrew Becker, Andrew Puckett and Jeremy Kubica at Apache Point Observatory in Sunspot, New Mexico. Ritona has a measured diameter of 679+55
    −73     km    , which is large enough that some astronomers consider it a possible dwarf planet.

    Contents

    Ritona has a dark and reddish surface made of water ice, carbon dioxide ice, carbon monoxide ice, and various organic compounds (tholins). Observations by the James Webb Space Telescope have shown that carbon dioxide ice is more abundant than water ice in Ritona's surface, which suggests that there is a thin layer of carbon dioxide ice covering Ritona's surface. Ritona is not known to have any natural satellites or moons, which means there is currently no way to measure its mass and density. [13] : 1, 3 

    History

    Discovery

    Ritona photographed in color by Apache Point Observatory's Sloan Digital Sky Survey on 18 and 19 October 2003, showing the object's slow movement across the sky Ritona SDSS 2003-10-18+19 annotated.gif
    Ritona photographed in color by Apache Point Observatory's Sloan Digital Sky Survey on 18 and 19 October 2003, showing the object's slow movement across the sky

    Ritona was discovered by astronomers Andrew Becker, Andrew Puckett and Jeremy Kubica on 10 September 2005, during observations for the Sloan Digital Sky Survey. [1] [14] The discovery observations were made using the 2.5-meter telescope at Apache Point Observatory in Sunspot, New Mexico. [14] The discoverers further observed Ritona until November 2005 and found the object in precovery observations from dates as early as June 2001. [14] The discovery of Ritona was announced by the Minor Planet Center on 23 July 2006. [14] Since then, Ritona has been found in even earlier precovery observations dating back to June 1954. [1]

    Name and number

    The object is named after Ritona, the Celtic goddess of river fords. [15] : 24  The naming of this object was announced by the International Astronomical Union's Working Group for Small Body Nomenclature on 21 July 2025. [15] : 24  Before Ritona was officially named, it was known by its provisional designation 2005 RN43, [1] which indicates the year and half-month of the object's discovery date. [16] Ritona's minor planet catalog number of 145452 was given by the Minor Planet Center on 5 December 2006. [17] The Kuiper belt objects 145451 Rumina and (145453) 2005 RR43 come before and after Ritona's number in the minor planet catalog, respectively. [17]

    Orbit

    Diagram showing Ritona's inclined orbit (gray) around the Sun, with the outer planets shown. The vertical gray lines along Ritona's orbital path mark its positions above and below the ecliptic plane. Ritona orbit diagram.png
    Diagram showing Ritona's inclined orbit (gray) around the Sun, with the outer planets shown. The vertical gray lines along Ritona's orbital path mark its positions above and below the ecliptic plane.

    Ritona is a trans-Neptunian object orbiting the Sun at a semi-major axis or average distance of 41.5  astronomical units (AU). [5] [b] It follows a moderately inclined and nearly circular orbit, [7] : 2537  with a low eccentricity of 0.02 and inclination of 19.3° with respect to the ecliptic. [5] In its 267-year-long orbit, Ritona comes as close as 40.6 AU from the Sun at perihelion and as far as 42.5 AU from the Sun at aphelion. [5] Ritona last passed perihelion in November 1760 and will make its next perihelion passage on 15 April 2029. [19] [6]

    Ritona is located in the classical region of the Kuiper belt 39–48 AU from the Sun, and is thus classified as a classical Kuiper belt object (sometimes known as a "cubewano"). [3] : 2–3  The high orbital inclination of Ritona makes it a dynamically "hot" member of the classical Kuiper belt. [3] : 3  The hot classical Kuiper belt objects are believed to have been scattered by Neptune's gravitational influence during the Solar System's early history. [20] : 230 

    Physical characteristics

    Size

    Ritona has a diameter of 679 km (422 mi) (full range 606 to 734 km or 377 to 456 mi when including uncertainties), according to thermal emission measurements by the infrared Herschel Space Observatory. [3] Ritona is large enough that some astronomers consider it a possible dwarf planet. [21] : 178  [13] : 1  [22] : 397 

    Surface

    The near-infrared spectrum of Ritona, as seen by the James Webb Space Telescope's NIRSpec instrument. Absorption signatures of chemical compounds are highlighted and labeled with their respective names. Ritona JWST-NIRSpec spectrum annotated.jpg
    The near-infrared spectrum of Ritona, as seen by the James Webb Space Telescope's NIRSpec instrument. Absorption signatures of chemical compounds are highlighted and labeled with their respective names.

    In visible light, the surface of Ritona appears dark and reddish in color, [9] [10] with a geometric albedo of about 0.11. [3] : 10  Spectroscopic observations by the James Webb Space Telescope (JWST) in 2022 have shown that Ritona's surface is composed of water ice, carbon dioxide (CO2) ice, carbon monoxide (CO) ice, and various organic compounds (tholins). [23] : 2  This composition is common among Kuiper belt objects. [23] Analysis of JWST's spectroscopic observations has shown that Ritona's surface is more abundant in CO2 ice than water ice, which suggests that Ritona's surface is covered with a thin (a few micrometres thick) layer of fine, micron-sized CO2 ice particles. [23] : 1–2  CO ice is also abundant in Ritona's surface, contrary to theoretical predictions that CO should sublimate and escape from Ritona's surface at its temperature and distance from the Sun. [23] : 1  Planetary scientists Michael E. Brown and Wesley C. Fraser have hypothesized that the Sun's ultraviolet light produces CO in Ritona's surface by irradiating and breaking down CO2 molecules, and leaves the CO trapped within the surrounding CO2 ice. [23] : 1, 5  A similar scenario has been hypothesized for (84522) 2002 TC302 , another CO2-rich Kuiper belt object observed by JWST. [23]

    Rotation

    As of 2018, observations of Ritona's brightness over time indicate it has a rotation period of either 6.946 or 13.892 hours, depending on whether the object's brightness variability is caused by surface albedo variations or an elongated shape. [a] [7] : 2537, 2542  Studies from 2010 to 2018 have consistently shown that Ritona exhibits very little brightness variation (less than 0.06 magnitudes), which makes it difficult to accurately determine its rotation period. [7] : 2539  The small brightness variations of Ritona can be explained if it has a spheroidal shape with small albedo variations across its surface. [21] : 177–178 

    See also

    Notes

    1. 1 2 3 The rotation period of Ritona was measured by observing how its brightness changes over time, which is plotted as a light curve. If Ritona has a spheroidal shape, then its light curve should resemble a "single-peaked" sine wave, whereas if Ritona is elongated, then its light curve should resemble a "double-peaked" sine wave. [7] : 2539 
    2. ↑ These orbital elements are expressed in terms of the Solar System Barycenter (SSB) as the frame of reference. [5] Due to planetary perturbations, the Sun revolves around the SSB at non-negligible distances, so heliocentric-frame orbital elements and distances can vary in short timescales as shown in JPL-Horizons. [18]

    References

    1. 1 2 3 4 5 6 "(145452) Ritona = 2005 RN43". Minor Planet Center. Retrieved 17 August 2025.
    2. 1 2 3 "JPL Small-Body Database Lookup: 145452 Ritona (2005 RN43)" (2025-05-30 last obs.). Jet Propulsion Laboratory . Retrieved 17 August 2025.
    3. 1 2 3 4 5 6 7 8 9 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 & Astrophysics. 541: 17. arXiv: 1204.0697 . Bibcode:2012A&A...541A..94V. doi: 10.1051/0004-6361/201118743 . S2CID   54222700. A94.
    4. ↑ Buie, Marc W. "Orbit Fit and Astrometric record for 145452". Southwest Research Institute. Archived from the original on 24 June 2025. Retrieved 17 August 2025.
    5. 1 2 3 4 5 "JPL Horizons On-Line Ephemeris for 145452 Ritona (2005 RN43) at epoch JD 2460800.5". JPL Horizons On-Line Ephemeris System . Jet Propulsion Laboratory. Retrieved 17 August 2025. Solution using the Solar System Barycenter. Ephemeris Type: Elements and Center: @0)
    6. 1 2 "JPL Horizons On-Line Ephemeris for 145452 Ritona (2005 RN43) from 2029-Jun-01 to 2029-Jun-30". JPL Horizons On-Line Ephemeris System . Jet Propulsion Laboratory. Retrieved 17 August 2025. (Perihelion occurs when deldot changes from negative to positive. Uncertainty in time of perihelion is 1-sigma from JPL Small-Body Database.)
    7. 1 2 3 4 Hromakina, T.; Perna, D.; Belskaya, I.; Dotto, E.; Rossi, A.; Bisi, F.; et al. (February 2018). "Photometric observations of nine Transneptunian objects and Centaurs" (PDF). Monthly Notices of the Royal Astronomical Society. 474 (2): 2536–2543. arXiv: 1712.04284 . Bibcode:2018MNRAS.474.2536H. doi: 10.1093/mnras/stx2904 . S2CID   119503877.
    8. ↑ Brunetto, R.; Hénault, E.; Cryan, S.; Pinilla-Alonso, N.; Emery, J. P.; Guilbert-Lepoutre, A.; et al. (March 2025). "Spectral Diversity of DiSCo's TNOs Revealed by JWST: Early Sculpting and Late Irradiation". The Astrophysical Journal Letters. 982 (1): L8. Bibcode:2025ApJ...982L...8B. doi: 10.3847/2041-8213/adb977 . S2CID   259287422. L8.
    9. 1 2 3 4 5 Belskaya, Irina N.; Barucci, Maria A.; Fulchignoni, Marcello; Lazzarin, M. (April 2015). "Updated taxonomy of trans-neptunian objects and centaurs: Influence of albedo". Icarus. 250: 482–491. Bibcode:2015Icar..250..482B. doi:10.1016/j.icarus.2014.12.004.
    10. 1 2 Barucci, M. A.; Merlin, F.; Perna, D.; Fornasier, S.; de Bergh, C. (September 2012). The reddest transneptunian objects (PDF). European Planetary Science Congress 2012. Vol. 7. Bibcode:2012epsc.conf..155B. EPSC2012-155.
    11. ↑ Brown, M. E.; Bannister, M. T; Schmidt, B. P.; Drake, A. J.; Djorgovski, S. G.; Graham, M. J.; et al. (February 2015). "A Serendipitous All Sky Survey for Bright Objects in the Outer Solar System". The Astronomical Journal. 149 (2): 69. arXiv: 1501.00941 . Bibcode:2015AJ....149...69B. doi: 10.1088/0004-6256/149/2/69 . S2CID   28115178. 69.
    12. ↑ Alvarez-Candal, A.; Pinilla-Alonso, N.; Ortiz, J. L.; Duffard, R.; Morales, N.; Santos-Sanz, P.; et al. (February 2016). "Absolute magnitudes and phase coefficients of trans-Neptunian objects". Astronomy & Astrophysics. 586: 33. arXiv: 1511.09401 . Bibcode:2016A&A...586A.155A. doi: 10.1051/0004-6361/201527161 . S2CID   119219851. A155.
    13. 1 2 Grundy, W. M.; McKinnon, W. B.; Ammannito, E.; Aung, M.; Bellerose, J.; Brenker, F.; et al. (December 2009). Exploration Strategy for the Ice Dwarf Planets 2013-2022 (PDF). American Geophysical Union Fall Meeting 2009. Bibcode:2009AGUFM.P43D1471G. P43D-1471. Archived from the original (PDF) on 30 March 2025.
    14. 1 2 3 4 Becker, A. C.; Puckett, A. W.; Kubika, J.; Williams, G. V. (23 July 2006). "MPEC 2006-O25 : 2005 RN43". Minor Planet Electronic Circular. 2006-O25. Minor Planet Center. Bibcode:2006MPEC....O...25B . Retrieved 17 August 2025.
    15. 1 2 "WGSBN Bulletin 5, #17" (PDF). WGSBN Bulletin. 5 (17). International Astronomical Union: 24. 21 July 2025. Retrieved 21 July 2025.
    16. ↑ "New- And Old-Style Minor Planet Designations". Minor Planet Center. Retrieved 17 August 2025.
    17. 1 2 "M.P.C. 58206" (PDF). Minor Planet Circulars (58206). Minor Planet Center: 160. 5 December 2006. Retrieved 21 July 2025.
    18. ↑ "JPL Horizons On-Line Ephemeris for 145452 Ritona (2005 RN43) at epochs JD 2460800.5–2461000.5". JPL Horizons On-Line Ephemeris System . Jet Propulsion Laboratory. Retrieved 17 August 2025. Solution using the Sun. Ephemeris Type: Elements and Center: @sun)
    19. ↑ "JPL Horizons On-Line Ephemeris for 145452 Ritona (2005 RN43) from 1760-Nov-01 to 1760-Nov-30". JPL Horizons On-Line Ephemeris System . Jet Propulsion Laboratory. Retrieved 17 August 2025. (Perihelion occurs when deldot changes from negative to positive. Uncertainty in time of perihelion is 1-sigma from JPL Small-Body Database.)
    20. ↑ Lykawka, Patryk Sofia; Tadashi, Mukai (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. S2CID   122671996.
    21. 1 2 Tancredi, Gonzalo (6 April 2010). "Physical and dynamical characteristics of icy "dwarf planets" (plutoids)". Proceedings of the International Astronomical Union. 5 (S263): 173–185. Bibcode:2010IAUS..263..173T. doi: 10.1017/S1743921310001717 .
    22. ↑ Pinilla-Alonso, Noemí; Stansberry, John; Holler, Bryan (2020). "Chapter 18 - Surface properties of large TNOs: Expanding the study to longer wavelengths with the James Webb Space Telescope". In Prialnik, Dina; Barucci, Maria Antonietta; Young, Leslie (eds.). The Transneptunian Solar System. Elsevier. pp. 395–412. arXiv: 1905.12320 . Bibcode:2019arXiv190512320P. doi:10.1016/B978-0-12-816490-7.00018-7. ISBN   978-0-12-816490-7.
    23. 1 2 3 4 5 6 Brown, Michael E.; Fraser, Wesley C. (July 2023). "The State of CO and CO2 Ices in the Kuiper Belt as Seen by JWST". The Planetary Science Journal. 4 (7): 130. arXiv: 2306.17051 . Bibcode:2023PSJ.....4..130B. doi: 10.3847/PSJ/ace2ba . S2CID   259287422. 130.
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