C/2017 U4 PANSTARRS
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Comet C/2017 U4 was discovered on 27 October 2017 with Pan-STARRS 1 telescope (Haleakala), that is about 11 months before its perihelion passage. Few prediscovery images of this comet were found: taken by the same survey from 2 January 2017. After perihelion passage this comet was observed rarely: in September and October 2018, and in February 2020.
Comet had its closest approach to the Earth on 11 December 2018 (6.761 au), about 2.5 months after its perihelion passage.
Solution given here is based on pre-perihelion data spanning over 1.77 yr in a range of heliocentric distances: 8.64 au – 7.724 au (perihelion) – 7.725 au.
This comet with original semimajor axis of about 8,500 au suffers tiny planetary perturbations during its passage through the planetary system.

solution description
number of observations 69
data interval 2017 01 02 – 2018 10 10
data type significantly more measurements before perihelion (PRE+)
data arc selection entire data set (STD)
range of heliocentric distances 8.64 au – 7.72 au (perihelion) – 7.72 au
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 128
RMS [arcseconds] 0.34
orbit quality class 1b
orbital elements (heliocentric ecliptic J2000)
Epoch 2018 10 09
perihelion date 2018 09 25.26939360 ± 0.01031500
perihelion distance [au] 7.72423551 ± 0.00005102
eccentricity 1.00367311 ± 0.00003550
argument of perihelion [°] 159.149483 ± 0.000698
ascending node [°] 245.950602 ± 0.000169
inclination [°] 158.226722 ± 0.000072
recip semi-major axis [10-6 au-1] -475.53 ± 4.58
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