C/2017 T2 PanSTARRS
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Comet C/2017 T2 was discovered on 2 October 2017 by Pan-STARRS 1 telescope (Haleakala) when it was 9.2 au from the Sun, that is about 7 months before its perihelion passage. Next, pre-discovery data were found going back to September 15. Comet was observed in four oppositions until 19 August 2021. C/2017 T1 had closest approach to the Earth on 28 December 2019 (1.52 au, about four months before the perihelion passage).
This is a comet with NG effects strongly manifested in positional data fitting and during GR orbit determination systematically small weights were obtained for post-perihelion observations since 2021 (last opposition). GR (solution 'ba') and NG (solutions 'en' and 'et' – asymmetric g(r)-function) orbits are based on data spanning over 3.925 yr in a range of heliocentric distances: 9.38 au – 1.615 au (perihelion) – 5.50 au. NG solution 'et' is given as preferred orbit; however still trend in [O-C] are visible for this orbit (see [O-C] picture). It is worth mentioning that solution 'et' is very similar in NG parameters and orbital elements to JPL's NG solution based on the same data arc (with the norm. resid. RMS of 0.504 arcsec; as in January 2025). Additionally, we suggest NG solutions 'pn' (based on the pre-perihelion orbital leg) or 'dd' (based on the pre-perihelion orbital leg up to heliocentric distance of 3.01 au) to be alsoused for for the study of the origin of this comet.
This Oort spike comet (original semimajor axis between 33,000–56,000 au, preferred solution: 37,000 au) suffers moderate planetary perturbations while passing through the planetary system; these perturbations lead to a more tight future orbit with semimajor axis of about 1370–1660 au.
This is a comet with NG effects strongly manifested in positional data fitting and during GR orbit determination systematically small weights were obtained for post-perihelion observations since 2021 (last opposition). GR (solution 'ba') and NG (solutions 'en' and 'et' – asymmetric g(r)-function) orbits are based on data spanning over 3.925 yr in a range of heliocentric distances: 9.38 au – 1.615 au (perihelion) – 5.50 au. NG solution 'et' is given as preferred orbit; however still trend in [O-C] are visible for this orbit (see [O-C] picture). It is worth mentioning that solution 'et' is very similar in NG parameters and orbital elements to JPL's NG solution based on the same data arc (with the norm. resid. RMS of 0.504 arcsec; as in January 2025). Additionally, we suggest NG solutions 'pn' (based on the pre-perihelion orbital leg) or 'dd' (based on the pre-perihelion orbital leg up to heliocentric distance of 3.01 au) to be alsoused for for the study of the origin of this comet.
This Oort spike comet (original semimajor axis between 33,000–56,000 au, preferred solution: 37,000 au) suffers moderate planetary perturbations while passing through the planetary system; these perturbations lead to a more tight future orbit with semimajor axis of about 1370–1660 au.
| solution description | ||
|---|---|---|
| number of observations | 1733 | |
| data interval | 2017 09 15 – 2019 10 15 | |
| data arc selection | data generally limited to pre-perihelion (PRE) | |
| range of heliocentric distances | 9.38 au – 3.01au | |
| type of model of motion | NC - non-gravitational orbits for symmetric CO-g(r)-like function | |
| data weighting | YES | |
| number of residuals | 3425 | |
| RMS [arcseconds] | 0.32 | |
| orbit quality class | 1b | |
| orbital elements (barycentric ecliptic J2000) | ||
|---|---|---|
| Epoch | 1720 11 20 | |
| perihelion date | 2020 05 05.00766582 | ± 0.00126927 |
| perihelion distance [au] | 1.61936250 | ± 0.00001038 |
| eccentricity | 0.99997156 | ± 0.00000398 |
| argument of perihelion [°] | 92.901784 | ± 0.000370 |
| ascending node [°] | 64.472747 | ± 0.000051 |
| inclination [°] | 57.141114 | ± 0.000069 |
| reciprocal semi-major axis [10-6 au-1] | 17.56 | ± 2.46 |
| file containing 5001 VCs swarm |
|---|
| 2017t2dd.bmi |
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).
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).
Six 2D-projections of the 6D space of original swarm including 5001 VCs. Each density map is given in logarithmic scale presented on the right in the individual panel.