145452 Ritona

With a diameter of roughly 679 km it is large enough that it has been described as a possible dwarf planet¹.

Discovery and naming

Ritona was discovered on 10 September 2005 by Andrew C. Becker, Andrew W. Puckett, and Jeremy M. Kubica at Apache Point Observatory near Sunspot, New Mexico^{2 • 3}. The Minor Planet Center published the discovery in MPEC 2006-O25 on 23 July 2006, together with the neighboring object 145451 Rumina, found by the same team⁴.

The name honors a Celtic water goddess. Ritona was a goddess of river fords among the Treveri, a Celtic tribe of the Moselle river valley in France; ancient inscriptions describe her as a protective deity of watercourses and of the ford across the Saar, and she has also been interpreted as a goddess of trade². The naming of the asteroid was announced by the International Astronomical Union's Working Group for Small Body Nomenclature on 21 July 2025, and the name appears in WGSBN Bulletin 5, #17⁵.

Orbit and classification

Because it lies in the classical Kuiper belt at 39 to 48 AU, Ritona is classified as a classical Kuiper belt object, sometimes called a cubewano.

Published orbit solutions disagree on the timing of the perihelion passages. One account states that Ritona last passed perihelion in November 1760 and will next pass it on 15 April 2029, while a computation from Minor Planet Center elements places the passages at 28 December 1766 and 12 November 2034³. The same Czech computation finds the object's closest approach to Earth in the coming decades at 39.56 AU on 28 September 2034, when it should also be near its brightest from Earth at magnitude 19.7³. Orbital simulations by NASA JPL's CNEOS show no close approaches to Earth¹.

Physical properties

The surface is red.

A 2017 photometric study of nine trans-Neptunian objects and centaurs improved the precision of the previously reported rotation period for 2005 RN₄₃ using both new and literature data⁶.

Observation record

Ritona is unusually well observed for a distant object. As of a May 2026 reference date, 1,250 observations across 31 oppositions spanning 1954 to 2025 had been used in the orbit solution, with the most recent observation on 6 December 2025³. This long observational arc is what allows a secure orbit for an object whose revolution period exceeds two and a half centuries.

References

1. Asteroid 145452 (2005 RN43), Space Reference
2. Ritona, Mark Andrew Holmes
3. Planetka Ritona (145452), Planety sluneční soustavy
4. Solar System Discovery Timeline, Solar System and the Universe Wiki
5. WGSBN Bulletin 5, #17, IAU Working Group for Small Body Nomenclature
6. Photometric observations of nine Transneptunian objects and Centaurs, arXiv:1712.04284

Topic: Encyclopedia › Places and geography › Extraterrestrial places › Small bodies of the Solar System › Kuiper belt and trans-Neptunian objects

Initially written Oct 21, 2026 · Edited: Oct 25, 2026

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