420356 Praamžius
A cold classical Kuiper belt object with an extremely circular orbit.
420356 Praamžius, also known by its provisional designation 2012 BX85, is a classical Kuiper belt object in the outer Solar System, with an estimated diameter between 190 and 320 kilometers. It was discovered on January 23, 2012, by Kazimieras Černis and Richard Boyle using the Vatican's 1.8-meter VATT telescope at Mount Graham Observatory in Arizona. The object is a cold classical Kuiper belt object, likely very red in color, and was named for Praamžius, the chief god in Lithuanian mythology.
Praamžius orbits the Sun at a distance ranging from 42.1 to 43.0 AU, completing one revolution every 277 years and 11 months. Its orbit has a semi-major axis of 42.59 AU, an eccentricity of 0.01, and an inclination of about 1° relative to the ecliptic. As a classical Kuiper belt object, it lies between the resonant plutino and twotino populations, and its low inclination (below 4–7°) places it in the cold population rather than the stirred hot one. In 2016, its eccentricity was 0.003, one of the lowest among trans-Neptunian objects and even lower than that of Venus, the least eccentric major planet (0.007). However, this eccentricity varies over time due to planetary influences; a 10-million-year simulation shows it never exceeds 0.03.
The discovery came from images taken on January 23, 2012, at VATT. Precovery observations from the same telescope and the Sloan Digital Sky Survey, dating back to December 31, 2002, were later accepted by the Minor Planet Center. The object was tracked regularly through January 2016, mostly by VATT with some support from Las Campanas Observatory. Praamžius is among the most recently discovered minor planets to receive a numeric designation, thanks to a well-determined orbit from frequent observations—averaging one every 23 to 24 days from 2002 to 2016, and as often as every 10 days between discovery and assignment. Precovery images further refined its orbit.
The minor planet was named after Praamžius ("the Eternal One," an epithet of Dievas), the Lithuanian god of sky, peace, and friendship. The naming citation was published by the Minor Planet Center on February 22, 2016, initially spelled "Praamzius." On May 4, 2026, the International Astronomical Union's Working Group for Small Body Nomenclature changed the spelling to "Praamžius."
Physical characteristics are uncertain.
Quick Facts
- Minorplanet
- yes
- Symbol
- (proposed)
- Background
- #C2E0FF
- Discoverer
- K. Černis / R. P. Boyle
- Discovery Site
- VATT (Mount Graham Obs.)
- Discovered
- 23 January 2012
- Mpc Name
- (420356) Praamžius
- Pronounced
- p · r · eɪ · ˈ · æ · m · ʒ · i · ə · s / (lt · prɐˈâmʑʊs · lang)
- Adjective
- Praamžinian
- Named After
- Praámžius / (Lithuanian mythology)
- Mp Category
- TNOcubewano / colddistant
- Epoch
- 27 April 2019 (JD 2458600.5)
Facts from the source article.
Lore & Background
Praamžius orbits the Sun at a distance of 42.1–43.0 AU once every 277 years and 11 months. Its orbit has an eccentricity of 0.01 and an inclination of 1° with respect to the ecliptic. It is a classical Kuiper belt object located between the resonant plutino and twotino populations, and with an inclination significantly less than 4–7°, it belongs to the cold rather than the stirred hot population. As of 2016, its eccentricity of 0.003 was one of the lowest of any trans-Neptunian object, and more circular than any major planet, though the eccentricity varies over time due to planetary positions; a 10 million year simulation shows it does not exceed 0.03.
The object was discovered from images acquired on 23 January 2012 at VATT using a 1.8 meter reflecting telescope. Precovery observations from VATT and the Sloan Digital Sky Survey dating back to 31 December 2002 were accepted by the Minor Planet Center. It was tracked through January 2016, mostly by VATT with supporting observations by Las Campanas Observatory. Praamžius is one of the most recently discovered minor planets to receive a numeric designation, due to the large number of observations: about one every 23 to 24 days on average from 2002 to 2016.
According to Johnston's Archive, Praamžius measures 321 kilometers in diameter based on an assumed albedo of 0.09, which would qualify it as a weak dwarf planet candidate under Michael Brown's 5-class taxonomic system. However, Brown estimates only 191 kilometers due to a higher assumed albedo of 0.20, and no longer considers it a possible dwarf planet. As of 2018, neither color indices nor a rotational lightcurve have been obtained, so its rotation period, pole, and shape remain unknown.
Reader's Guide
420356 Praamžius is significant as a cold classical Kuiper belt object with an exceptionally low orbital eccentricity, which as of 2016 was one of the lowest among trans-Neptunian objects and more circular than any major planet. Its discovery and precovery observations spanning from 2002 to 2016 allowed for a well-determined orbit, making it one of the most recently discovered minor planets to receive a numeric designation. The object's size remains uncertain, with estimates ranging from 191 to 321 kilometers depending on the assumed albedo, leading to disagreement about its status as a dwarf planet candidate. Its naming after the chief god Praamžius from Lithuanian mythology reflects a tradition of honoring mythological figures. The object's physical characteristics, including color and rotation, have not yet been determined, leaving many aspects of its nature unknown.
Did You Know?
- Praamžius was discovered on 23 January 2012 by astronomers Kazimieras Černis and Richard Boyle using the Vatican's VATT at Mount Graham Observatory in Arizona.
- The object is named after Praamžius, the Lithuanian god of the sky, peace, and friendship.
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