C/2014 UN271 Bernardinelli-Bernstein
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The discovery of C/2014 UN271 was announced in June 2021 by Bernardinelli & Bernstein (2021) on the basis of astrometric observations spanning 20 nights from 20 October 2014 to 8 November 2018 (29.0 au–23.7 au from the Sun). A little later, at a heliocentric distance of over 20 au, observers reported the cometary activity of C/2014 UN271.

The comet will pass through perihelion (10.95 au from the Sun) on 22 January 2031; thus solutions given here are currently based on pre-perihelion data taken at large heliocentric distances.

GR solution 'b8' perfectly fits the data; however, GR solution 'd5' based on longer data arc shows that something happened at the end of 2021 because some trend are visible in the period 2010-2020. For example, there may have been some more violent activity associated with the breakaway of a comet fragment as early as late 2021 (heliocentric distance of about 20 au; see [O-C] for the 'ba' solution). These trends in [O-C] indicates that the outburst reported by Kokotanekova et al (2024) was associated with a noticeable action of NG acceleration forces on the comet's motion. This is all the more interesting because it is a very large comet, with a size estimated at 60 km thanks to ALMA and HST observations.

Most probably, this Oort spike comet suffers small planetary perturbations during its passage through the planetary system.

More details about orbital fitting before the year 2022: see Dybczyński and Królikowska (2022)
solution description
number of observations 134
data interval 2010 11 15 – 2022 02 13
data arc selection data generally limited to pre-perihelion (PRE)
range of heliocentric distances 34.07 au – 19.31au
detectability of NG effects in the comet's motion NG effects not determinable
type of model of motion GR - gravitational orbit
data weighting YES
number of residuals 248
RMS [arcseconds] 0.16
orbit quality class 1a+
orbital elements (heliocentric ecliptic J2000)
Epoch 2031 01 14
perihelion date 2031 01 22.94615521 ± 0.01295293
perihelion distance [au] 10.95017329 ± 0.00007465
eccentricity 1.00070598 ± 0.00000658
argument of perihelion [°] 326.321351 ± 0.000375
ascending node [°] 190.023556 ± 0.000025
inclination [°] 95.454533 ± 0.000023
reciprocal semi-major axis [10-6 au-1] -64.47 ± 0.60
Upper panel: Time distribution of positional observations with corresponding heliocentric (red curve) and geocentric (green curve) distance at which they were taken. The horizontal dotted line shows the perihelion distance for a given comet whereas vertical dotted line — the moment of perihelion passage.
Middle panel(s): O-C diagram for a given solution (sometimes in comparison to another solution available in CODE), where residuals in right ascension are shown using magenta dots and in declination by blue open circles.
Lowest panel: Relative weights for a given data set(s).