C/1978 G2 McNaught-Tritton

Solar System
Dynamics &
Planetology
Group

General description

Comet C/1978 G2 was discovered on 12 April 1978, more than four months before its perihelion passage, and was last seen on 23 January 1980 [Kronk and Meyer, Cometography: Volume 5].

The comet made its closest approach to the Earth on 29 April 1978 (5.38 au), that was 17 days after its discovery.

Solution given below is based on data span over 1.78 yr in the range of heliocentric distances: 6.35 au – 6.28 au (perihelion) – 7.20 au, however only seven measurements are known for this comet.

Comet suffered rather small planetary perturbations during its passage through the planetary system.

Figure caption: 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.

SSDP Cometary Note C1978G2_S-001

Comet C/1978 G2 McNaught-Tritton

number of observations	7
number of residuals	14
data interval	1978 Apr. 12 — 1980 Jan. 23
rms [arcsec]	0.82
orbit quality class	1a

Osculating orbital elements (heliocentric; ecliptic J2000.0)

Epoch (TT)	19780909.0	= JD 2443760.5
time of perihelion passage (TT)	19780824.540076	± 0.027455
perihelion distance	6.28283701	± 0.00026742
eccentricity	1.00213685	± 0.00023866
argument of perihelion [deg]	229.509423	± 0.002489
longitude of the ascending node [deg]	72.215982	± 0.000451
inclination [deg]	153.182919	± 0.000230
inverse semimajor axis [10^-6 au^-1]	-340.11	± 37.94

Note: Epoch is given in a format: yyyymmdd.d, time of perihelion passage in a format of yyyymmdd.dddddd.

Figure caption: Six 2D-projections of the 6D space of original swarm (5001 VCs) of C/1978 G2. Each density map is given in logarithmic scale presented on the right in the individual panel.
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Original orbital elements (barycentric; at 250 au from the Sun)

Epoch (TT)	16710809
time of perihelion passage (TT)	19780826.698113	± 0.026870
perihelion distance	6.28038625	± 0.00026610
eccentricity	1.00014083	± 0.00023760
argument of perihelion [deg]	229.651662	± 0.002461
longitude of the ascending node [deg]	72.211404	± 0.000457
inclination [deg]	153.162815	± 0.000234
inverse semimajor axis [10^-6 au^-1]	-22.42	± 37.83

Note: Values of uncertainties of original/future orbital elements were derived using a swarm of 5001 osculating orbits of VCs (including the nominal osculating orbit given above) for original/future orbital evolution calclulations and then by fitting the distribution of a given orbital element of original/future swarm of VCs to Gaussian distribution.

Original barycentric positions and velocities of 5001 VCs at 250 au from the Sun are given here (data format), i.e. before entering the planetary zone.

Future orbital elements (barycentric; at 250 au from the Sun)

Epoch (TT)	22841014
time of perihelion passage (TT)	19780825.628227	± 0.027360
perihelion distance	6.27935179	± 0.00026690
eccentricity	1.00062275	± 0.00023752
argument of perihelion [deg]	229.662065	± 0.002455
longitude of the ascending node [deg]	72.306967	± 0.000450
inclination [deg]	153.149555	± 0.000233
inverse semimajor axis [10^-6 au^-1]	-99.17	± 37.82