Praamzius 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 has an excite_mean of 0.053. It is a classical Kuiper belt object located in between the resonant plutino and twotino populations and has a low-eccentricity orbit. With an inclination significantly less than 4–7°, it belongs to the cold rather than to the "stirred" hot population. With an eccentricity of 0.003 in 2016, Praamzius had one of the lowest eccentricities of any trans-Neptunian object, and a more circular orbit than any major planet. But the object's eccentricity varies over time due to the position of the planets . A 10 million year simulation of the orbit shows the eccentricity does not get greater than 0.03.
Its orbital radius is near, but not actually on the 3:5 resonance with Neptune, with both period and radius being slightly too large to achieve an exact. This could be due to any of several reasons, e.g. their apparent relationship being merely coincidental and Praamzius a typical non-resonant cubewano instead of resonant, or an artefact of librating cycle centred on 3:5 and currently on the longer/wider limb of its oscillation around that, or due to it exhibiting some more exotic resonance such as 7:12, 10:17 or 17:28 which are better fits for its observed track. However, it is difficult to yet determine which of these is true, as although Praamzius has a comparatively good observational record, with an otherwise decent orbital uncertainty of 2, or a mere 4.4 to 19.6 arcseconds of drift expected per decade, its great orbital distance and long period mean each of its approximately 28-decade orbits accumulate 0.034 to 0.153 degrees of potential error. Whilst still a very small amount, and unlikely to cause any difficulty with predicting target areas for future imaging or the object's position for probe rendezvous, it is enough to make nearly all of the above scenarios possible. The apparent resonance even depends on what source data and calculation methods are employed - the best fit for the given orbital periods within a 25,000 year cycle time, 44:75, is still imperfect and exhibits a final error of more than 1.5 Earth years for the final conjunction. If we instead use the two bodies' respective semi-major axes, i.e. their mean orbital radii as the basis for calculation, and purely Keplerian 2-body equations, the decimal ratio returns 1.699943. This is actually close enough to 1.7 that a 10:17 resonance can be considered a credible possibility, not only with U = 2, but even in the looser reaches of a notional "U=-1" band, 4.4× more accurate than the usual U = 0 gold standard and about 85× more than band 2. However, appearing to be dead centre is no guarantee of accuracy when the uncertainty IS actually that great, so either of the other explanations could still be correct.
Discovery
Initial discovery was from images acquired on 23 January 2012 at VATT, on Mount Graham, Arizona using a 1.8 meter reflecting telescope; precovery observations from VATT and the Sloan Digital Sky Survey dating back to 31 December 2002 have been accepted by the Minor Planet Center. The object has been repeatedly tracked through January 2016, mostly by VATT with some supporting observations by Las Campanas Observatory. 420356 Praamzius is one of the most recently discovered minor planets to receive a numeric designation, confirming it as a distinct body with a well determined orbit. This is due to the large number of observations since and indeed before its discovery: about one every 23 to 24 days on average from 2002 to 2016, and as many as one per 10 days in the period between discovery and assignment alone. Precovery images refined the orbit even more.
According to Johnston's archive, Praamzius measures 321 kilometers in diameter based on an assumed, generic albedo of 0.09. This would qualify the object as a weak dwarf planet candidate based on the 5-class taxonomic system of American astronomer Michael Brown. However, on his website, Brown estimates only a diameter of 191 kilometers due to a much higher albedo of 0.20. As a consequence, he no longer considers Praamzius to be a possible dwarf planet. As of 2018, neither the body's color indices, nor its rotational lightcurve has been obtained from photometric observations, and its rotation period, pole and shape remain unknown. Analysis of precovery observations in the visible spectrum between 2002 and 2007 show that it may be amongst the reddest objects in the Solar System, being more than 1.5 magnitudes fainter in the G filtered versus the R filtered images, which may offer some clues about its composition and origin . This is expected from a fairly small "orbitally unexcited" cold Classical Kuiper belt object as they are generally mostly red. The cold populations distance does not vary from the Sun very much so their surfaces are older, more irradiated, and covered in tholins. There is a chance it accreted in basically the same orbit it has today.
