145452 Ritona

Classical Kuiper belt object 145451 Rumina August 2025 yes possible dwarf planet 145452 Ritona Ritona Hubble 2010 north-up.png Ritona imaged by the Hubble Space Telescope on 25 April 2010 Andrew C. Becker Andrew W. Puckett Jeremy M. Kubica Apache Point Obs. 10 September 2005 (145452) Ritona 2005 RN 43 Ritona TNO classical (hot) distant Scat-Ext 5 May 2025 (JD 2460800.5) 0 70.99 yr (25930 days) 2 June 1954 yes 42.450 AU 40.575 AU ≈ 15 June 2029 41.512 AU 0.0226 267.29 yr (97,627 d) 352.812° 0.0036875 ms / day 19.274° 186.989° 172.899° 0 679 55 73 km 6.946 0.05 h (single-peaked)rotation 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.2539 or 13.892 0.05 h (double-peaked)rotation 0.107 0.029 0.018 CO 2-type ("double-dip") IR–RR (red) B–V 0.95 0.02 V–R 0.59 0.01 V–I 1.08 0.02 3.882 0.036 (2016)14 3.89 0.05 (2012)3 3.69 (JPL) ≈ 20 (average)5 43.2 K (perihelion)11 145452 Ritona (provisional designation 2005 RN 43) is a large trans-Neptunian object 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. 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.1, 3 History Discovery Ritona was discovered by astronomers Andrew Becker, Andrew Puckett and Jeremy Kubica on 10 September 2005, during observations for the Sloan Digital Sky Survey. The discovery observations were made using the 2.5-meter telescope at Apache Point Observatory in Sunspot, New Mexico. The discoverers further observed Ritona until November 2005 and found the object in precovery observations from dates as early as June 2001. The discovery of Ritona was announced by the Minor Planet Center on 23 July 2006. Since then, Ritona has been found in even earlier precovery observations dating back to June 1954. horizontal center 500 SDSS (Crop of Apache-0110).JPG Ritona SDSS 2003-10-18+19 annotated.gif Ritona was discovered in 2005 by Apache Point Observatory's 2.5-meter telescope in Sunspot, New Mexico (pictured) 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 Name and number The object is named after Ritona, the Celtic goddess of river fords.24 The naming of this object was announced by the International Astronomical Union's Working Group for Small Body Nomenclature on 21 July 2025.24 Before Ritona was officially named, it was known by its provisional designation 2005 RN 43, which indicates the year and half-month of the object's discovery date. Ritona's minor planet catalog number of 145452 was given by the Minor Planet Center on 5 December 2006. Orbit and classification thumb|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. Orbital characteristics Ritona is a trans-Neptunian object orbiting the Sun at a semi-major axis or average distance of 41.5 astronomical units (AU).barycentric 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 can vary in short timescales as shown in JPL-Horizons. It follows a moderately inclined and nearly circular orbit,2537 with a low eccentricity of 0.02 and inclination of 19.3° with respect to the ecliptic. 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. Ritona last passed perihelion in November 1760 and will make its next perihelion passage on 15 April 2029. Classification 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").2–3 The high orbital inclination of Ritona makes it a dynamically "hot" member of the classical Kuiper belt.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.230 Physical characteristics Size Ritona has a diameter of 679 km mi (full range 606 to 734 km mi or when including uncertainties), according to thermal emission measurements by the infrared Herschel Space Observatory. Ritona is large enough that some astronomers consider it a possible dwarf planet.1781397 However, based on its size of 606 to 734 km, it belongs to the proposed class of "mid-sized" TNOs between 400 and 1000 km mi in diameter, which are believed to represent the transition between small, low-density TNOs and large, high-density dwarf planets.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. Surface thumb|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, with a geometric albedo of about 0.11.10 Spectroscopic observations by the James Webb Space Telescope (JWST) in 2022 have shown that Ritona's surface is composed of water ice, carbon dioxide (CO 2) ice, carbon monoxide (CO) ice, and various organic compounds (tholins).2 Ritona shares this composition with the CO 2-type (aka "double-dip") trans-Neptunian objects, which are commonly found on dynamically excited orbits such as those in the hot classical Kuiper belt (where Ritona resides).234, 236CO2-type The "double-dip" TNO spectral type were later renamed to the "CO 2-type" in 2025. Analysis of JWST's spectroscopic observations has shown that Ritona's surface is more abundant in CO 2 ice than water ice, which suggests that Ritona's surface is covered with a thin (a few micrometres thick) layer of fine, micron-sized CO 2 ice particles.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.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 CO 2 molecules, and leaves the CO trapped within the surrounding CO 2 ice.1, 5 A similar scenario has been hypothesized for (84522) 2002 TC 302, another CO 2-rich Kuiper belt object observed by JWST. The surface temperature of Ritona at perihelion (closest point to the Sun) is estimated to be approximately 43.2 Kelvin.11 Rotation 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.rotation2537, 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.2539 The small brightness variations of Ritona can be explained if it has a spheroidal shape with small albedo variations across its surface.177–178 See also List of possible dwarf planets 90568 Goibniu – a classical Kuiper belt object and possible dwarf planet similar to Ritona in size List of Solar System objects by size Notes References 30em 2025-05-30 last obs. JPL Small-Body Database Lookup: 145452 Ritona (2005 RN43) https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=20145452 Jet Propulsion Laboratory 2025-08-17 (145452) Ritona = 2005 RN43 https://www.minorplanetcenter.net/db_search/show_object?object_id=145452 Minor Planet Center 2025-08-17 New- And Old-Style Minor Planet Designations https://www.minorplanetcenter.net/iau/info/DesDoc.html Minor Planet Center 2025-08-17 JPL Horizons On-Line Ephemeris for 145452 Ritona (2005 RN43) at epoch JD 2460800.5 https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND='145452'&TABLE_TYPE='ELEMENTS'&START_TIME='JD2460800.5'&STOP_TIME='JD2460801.5'&STEP_SIZE='1y'&CENTER='@0'&OUT_UNITS='AU-D' JPL Horizons On-Line Ephemeris System Jet Propulsion Laboratory 2025-08-17 Solution using the Solar System Barycenter. Ephemeris Type: Elements and Center: @0) JPL Horizons On-Line Ephemeris for 145452 Ritona (2005 RN43) at epochs JD 2460800.5–2461000.5 https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND='145452'&TABLE_TYPE='ELEMENTS'&START_TIME='JD2460800.5'&STOP_TIME='JD2461000.5'&STEP_SIZE='200d'&CENTER='500@10'&OUT_UNITS='AU-D' JPL Horizons On-Line Ephemeris System Jet Propulsion Laboratory 2025-08-17 Solution using the Sun. Ephemeris Type: Elements and Center: @sun) JPL Horizons On-Line Ephemeris for 145452 Ritona (2005 RN43) from 1760-Nov-01 to 1760-Nov-30 https://ssd.jpl.nasa.gov/api/horizons.api?format=text&COMMAND=%27145452%27&OBJ_DATA=%27YES%27&MAKE_EPHEM=%27YES%27&EPHEM_TYPE=%27OBSERVER%27&CENTER=%27@sun%27&START_TIME=%271760-11-01%27&STOP_TIME=%271760-11-30%27&STEP_SIZE=%271d%27&QUANTITIES=%2720%27 JPL Horizons On-Line Ephemeris System Jet Propulsion Laboratory 2025-08-17 (Perihelion occurs when deldot changes from negative to positive. Uncertainty in time of perihelion is 1-sigma from JPL Small-Body Database.) JPL Horizons On-Line Ephemeris for 145452 Ritona (2005 RN43) from 2029-Jun-01 to 2029-Jun-30 https://ssd.jpl.nasa.gov/api/horizons.api?format=text&COMMAND=%27145452%27&OBJ_DATA=%27YES%27&MAKE_EPHEM=%27YES%27&EPHEM_TYPE=%27OBSERVER%27&CENTER=%27@sun%27&START_TIME=%272029-06-01%27&STOP_TIME=%272029-06-30%27&STEP_SIZE=%271d%27&QUANTITIES=%2720%27 JPL Horizons On-Line Ephemeris System Jet Propulsion Laboratory 2025-08-17 (Perihelion occurs when deldot changes from negative to positive. Uncertainty in time of perihelion is 1-sigma from JPL Small-Body Database.) Orbit Fit and Astrometric record for 145452 http://www.boulder.swri.edu/~buie/kbo/astrom/145452.html Marc W. Buie Southwest Research Institute 2025-08-17 live https://web.archive.org/web/20250624075027/http://www.boulder.swri.edu/~buie/kbo/astrom/145452.html 2025-06-24 A. C. Becker A. W. Puckett J. Kubika G. V. Williams Gareth V. Williams MPEC 2006-O25 : 2005 RN43 https://www.minorplanetcenter.net/mpec/K06/K06O25.html Minor Planet Electronic Circular Minor Planet Center 2006-07-23 2006-O25 2025-08-17 2006MPEC....O...25B Patryk Sofia Lykawka Mukai Tadashi Dynamical classification of trans-neptunian objects: Probing their origin, evolution, and interrelation Icarus July 2007 189 1 213–232 10.1016/j.icarus.2007.01.001 2007Icar..189..213L 122671996 Gonzalo Tancredi Physical and dynamical characteristics of icy "dwarf planets" (plutoids) Proceedings of the International Astronomical Union 6 April 2010 5 S263 173–185 free 10.1017/S1743921310001717 2010IAUS..263..173T etal W. M. Grundy W. B. McKinnon E. Ammannito M. Aung J. Bellerose F. Brenker Exploration Strategy for the Ice Dwarf Planets 2013-2022 https://www.lpi.usra.edu/decadal/sbag/community_wp/SB_Community_WP_Final_Dwarfs.pdf American Geophysical Union Fall Meeting 2009 December 2009 P43D-1471 2009AGUFM.P43D1471G dead https://web.archive.org/web/20250330030249/https://www.lpi.usra.edu/decadal/sbag/community_wp/SB_Community_WP_Final_Dwarfs.pdf 2025-03-30 M. A. Barucci F. Merlin D. Perna S. Fornasier C. de Bergh The reddest transneptunian objects https://meetingorganizer.copernicus.org/EPSC2012/EPSC2012-155.pdf European Planetary Science Congress 2012 September 2012 7 EPSC2012-155 2012epsc.conf..155B etal E. Vilenius C. Kiss M. Mommert T. Müller P. Santos-Sanz A. Pal "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 May 2012 541 A94 17 free 10.1051/0004-6361/201118743 1204.0697 2012A&A...541A..94V 54222700 etal M. E. Brown Michael E. Brown M. T Bannister Michele Bannister B. P. Schmidt A. J. Drake S. G. Djorgovski M. J. Graham A Serendipitous All Sky Survey for Bright Objects in the Outer Solar System The Astronomical Journal February 2015 149 2 69 69 free 10.1088/0004-6256/149/2/69 1501.00941 2015AJ....149...69B 28115178 Updated taxonomy of trans-neptunian objects and centaurs: Influence of albedo Irina N. Belskaya Maria A. Barucci Marcello Fulchignoni M. Lazzarin April 2015 Icarus 250 482–491 10.1016/j.icarus.2014.12.004 2015Icar..250..482B etal A. Alvarez-Candal N. Pinilla-Alonso J. L. Ortiz R. Duffard N. Morales P. Santos-Sanz Absolute magnitudes and phase coefficients of trans-Neptunian objects Astronomy & Astrophysics February 2016 586 A155 33 free 10.1051/0004-6361/201527161 1511.09401 2016A&A...586A.155A 119219851 etal T. Hromakina D. Perna I. Belskaya E. Dotto A. Rossi F. Bisi Photometric observations of nine Transneptunian objects and Centaurs https://www.astrofit2.inaf.it/wp-content/uploads/2018/07/Hromakina2018.pdf Monthly Notices of the Royal Astronomical Society February 2018 474 2 2536–2543 free 10.1093/mnras/stx2904 1712.04284 2018MNRAS.474.2536H 119503877 Dina Prialnik Maria Antonietta Barucci Leslie Young Noemí Pinilla-Alonso John Stansberry Bryan Holler The Transneptunian Solar System Chapter 18 - Surface properties of large TNOs: Expanding the study to longer wavelengths with the James Webb Space Telescope Elsevier 2020 395–412 10.1016/B978-0-12-816490-7.00018-7 1905.12320 2019arXiv190512320P 978-0-12-816490-7 Michael E. Brown Michael E. Brown Wesley C. Fraser The State of CO and CO2 Ices in the Kuiper Belt as Seen by JWST The Planetary Science Journal July 2023 4 7 130 130 free 10.3847/PSJ/ace2ba 2306.17051 2023PSJ.....4..130B 259287422 etal Noemí Pinilla-Alonso Rosario Brunetto Mário N. De Prá Bryan J. Holler Elsa Hénault Ana Carolina de Souza Feliciano A JWST/DiSCo-TNOs portrait of the primordial Solar System through its trans-Neptunian objects Nature Astronomy December 2024 9 2 230–244 10.1038/s41550-024-02433-2 2025NatAs...9..230P 274932942 etal R. Brunetto E. Hénault S. Cryan N. Pinilla-Alonso J. P. Emery A. Guilbert-Lepoutre Spectral Diversity of DiSCo's TNOs Revealed by JWST: Early Sculpting and Late Irradiation The Astrophysical Journal Letters March 2025 982 1 L8 free 10.3847/2041-8213/adb977 2025ApJ...982L...8B 259287422 WGSBN Bulletin 5, #17 https://wgsbn-iau.org/files/Bulletins/V005/WGSBNBull_V005_017.pdf#page=24 WGSBN Bulletin International Astronomical Union 5 17 24 21 July 2025 21 July 2025 W. M. Grundy K. S. Noll M. W. Buie S. D. Benecchi D. Ragozzine H. G. Roe The Mutual Orbit, Mass, and Density of Transneptunian Binary Gǃkúnǁʼhòmdímà ((229762) 2007 UK 126) http://www2.lowell.edu/users/grundy/abstracts/preprints/2019.G-G.pdf Icarus December 2019 334 30–38 10.1016/j.icarus.2018.12.037 2019Icar..334...30G 126574999 7 April 2019 6 April 2026 https://web.archive.org/web/20190407045339/http://www2.lowell.edu/~grundy/abstracts/preprints/2019.G-G.pdf dead Scott Sheppard Yanga Fernandez Arielle Moullet The Albedos, Sizes, Colors and Satellites of Dwarf Planets Compared with Newly Measured Dwarf Planet 2013 FY27 The Astronomical Journal 156 6 270 6 September 2018 1809.02184 10.3847/1538-3881/aae92a 2018AJ....156..270S 119522310 free etal Bryan J. Holler Rosario Brunetto Dale P. Cruikshank Sasha Cryan Aurelie Guilbert-Lepoutre Brittany Harvison A Descriptive Taxonomic Nomenclature for Intermediate-sized Trans-Neptunian Object Spectra Research Notes of the American Astronomical Society September 2025 9 9 241 free 10.3847/2515-5172/ae03a2 2025RNAAS...9..241H External links 145452 145452 145451 Rumina 145452 (145453) 2005 RR43 Category:Classical Kuiper belt objects Ritona Ritona Ritona 20050910 Category:Possible dwarf planets Ritona Category:Minor planets named after their provisional designation Ritona