C/2017 S7 Lemmon
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Comet C/2017 S7 was discovered on 26 September 2017 with Mount Lemmon survey, that is about 4 months after its perihelion passage. Several prediscovery images of this comet were found: taken by the same survey from 18, 27 and 30 of December 2016. This comet was observed until 4 December 2018.

Comet had its closest approach to the Earth on 18 December 2016 (6.698 au), exactly the same day as the first pre-discovery image were taken; almost 5.5 months before its perihelion passage.

The preferred solution given here is based on data spanning over 2.89 yr in a range of heliocentric distances: 8.22 au – 7.61 au (perihelion) – 8.22 au.

This near-parabolic comet suffers insignificant planetary perturbations during its passage through the planetary system (original and future semimajor axes between 9,000 and 10,000 au).
solution description
number of observations 153
data interval 2016 12 18 – 2018 11 15
data type perihelion within the observation arc (FULL)
data arc selection entire data set (STD)
range of heliocentric distances 7.68 au – 7.62 au (perihelion) – 8.31 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 298
RMS [arcseconds] 0.37
orbit quality class 1a
orbital elements (barycentric ecliptic J2000)
Epoch 2328 04 07
perihelion date 2017 05 27.01266278 ± 0.00459074
perihelion distance [au] 7.61842030 ± 0.00001015
eccentricity 0.99918944 ± 0.00000944
argument of perihelion [°] 187.662638 ± 0.000316
ascending node [°] 262.763480 ± 0.000022
inclination [°] 124.191307 ± 0.000045
reciprocal semi-major axis [10-6 au-1] 106.39 ± 1.24
file containing 5001 VCs swarm
2017s7b5.bpl
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.
Six 2D-projections of the 6D space of future swarm including 5001 VCs. Each density map is given in logarithmic scale presented on the right in the individual panel.