C/2017 S6 Catalina
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Comet C/2017 S6 was discovered on 30 September 2017 during Catalina Sky Survey, that is 5 months before its perihelion passage. Next, single measurements were found taken at Kitt Peakon 26 February 2017. Comet was observed only on its pre-perihelion leg of orbit until 24 January 2018 (about one month before perihelion). Comet had closest approach to the Earth on 26 November 2017 (1.212 au, about two months after discovery).

Only GR orbit is possible to obtain. GR solution 'a5' is based on data spanning over 0.934 yr in a range of heliocentric distances from 4.67 au to 1.61 au along pre-peperihelion orbital leg whereas 'p2' is based on shorter data arc spanning over 0.79 yr to a heliocentric distance of 1.95 au.

This Oort spike comet suffers moderate planetary perturbations while passing through the planetary system and these perturbations lead to escape the comet from the planetary zone on a hyperbolic orbit (see future barycentric orbit).
solution description
number of observations 188
data interval 2017 02 16 – 2017 11 30
data arc selection data generally limited to pre-perihelion (PRE)
range of heliocentric distances 4.67 au – 1.95au
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 374
RMS [arcseconds] 0.59
orbit quality class 1b
orbital elements (heliocentric ecliptic J2000)
Epoch 2018 02 23
perihelion date 2018 02 26.93160577 ± 0.00142858
perihelion distance [au] 1.54294542 ± 0.00000844
eccentricity 1.00138367 ± 0.00002490
argument of perihelion [°] 134.686090 ± 0.000788
ascending node [°] 130.875041 ± 0.000125
inclination [°] 152.826661 ± 0.000046
reciprocal semi-major axis [10-6 au-1] -896.77 ± 16.13
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).