C/2017 M4 ATLAS
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Comet C/2017 M4 was discovered on 21 June 2017 by Asteroid Terrestrial-impact Last Alert System (ATLAS) Team, that is about  months after its perihelion passage.

Some prediscovery images of this comet were found: taken on 16 June 2017 by Pan-STARRS 1 telescope (Haleakala).

Solutions given here are based on data spanning over 4.46 yr in a range of heliocentric distances: 6.09 au – 3.252 au (perihelion) – 9.19 au.

NG orbits using full data-arc as well as independently using pre-perihelion and post-perihelion data are determinable.

See also Królikowska and Dones 2023.
solution description
number of observations 3284
data interval 2017 06 16 – 2021 11 30
data type perihelion within the observation arc (FULL)
data arc selection entire data set (STD)
range of heliocentric distances 6.09 au – 3.25 au (perihelion) – 9.19 au
type of model of motion NT - non-gravitational orbits for asymmetric, standard g(r)
data weighting YES
number of residuals 6492
RMS [arcseconds] 0.47
orbit quality class 1a+
orbital elements (heliocentric ecliptic J2000)
Epoch 2019 02 06
perihelion date 2019 01 18.17453390 ± 0.00021476
perihelion distance [au] 3.25176758 ± 0.00000113
eccentricity 1.00228882 ± 0.00000238
argument of perihelion [°] 167.618305 ± 0.000047
ascending node [°] 65.867457 ± 0.000006
inclination [°] 105.657174 ± 0.000007
reciprocal semi-major axis [10-6 au-1] -703.87 ± 0.73
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).
non-gravitational parameters
A1 [10-8au/day2] 863.27 ± 14.23
A2 [10-8au/day2] 136.073 ± 15.441
A3 [10-8au/day2] 212.9 ± 4.015
m -2.15
n 5.093
k -4.6142
r0 [au] 2.808
α 0.1113
ΔT [days] -23.9000 ± 3.1