Solar System
Dynamics &
Planetology
Group 		C/1921 E1 Reid



General description

data set of C/1921 E1

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Comet C/1921 E1 was discovered on 14 March 1921, almost two months before its perihelion passage, and was last seen on 26 November 1921 [Kronk, Cometography: Volume 3].

This comet made its closest approach to the Earth on 29 April 1921 (0.628 au), that is 1.5 month after its discovery, and 11 days before perihelion passage.

Solution given below is based on data span over 0.701 yr in a range of heliocentric distances from 1.376 au through perihelion (1.008 au) to 3.075 au.

Comet suffered rather small planetary perturbations during its passage through the planetary system, however, they led to escape the comet from the planetary zone on a hiperbolic orbit (see future barycentric orbits given below).

Pure gravitational orbit determined from all available positional measurements (568 observations) give 2a-class orbit similarly as in Minor Planet Center (146 obs. used, the same arc of data; 2A class, see MPC).
However, using the purely gravitational model of motion the original barycentric orbit is hyperbolic, whereas GR orbit obtained by Marsden (1978) using only 26% of data gave original elliptical orbit (Marsden, Sekanina and Everhart 1978, see also MPC).

It was possible to determine the non-gravitational orbit for C/1921 E1; the decrease of RMS is insignificant, however the trend in O-C giving negative residuals in all RA and DEC measurements at the end of the data interval (October and November) was cancelled. The derived NG solution give elliptical orbit with original barycentric 1/a inside the Oort spike (orbit of 2b-class, see NG solution given below).

More details in Królikowska et al. 2014


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.




Non–gravitational orbit — see below SSDP Cometary Note C1921E1N6-001

SSDP Cometary Note C1921E1A5-001

Comet C/1921 E1 Reid

number of observations 568
number of residuals 914
data interval 1921 Mar. 15 — 1921 Nov. 26
rms [arcsec] 3.27
orbit quality class 2a

Osculating orbital elements (heliocentric; ecliptic J2000.0)

Epoch (TT) 19210421.0 = JD 2422800.5
time of perihelion passage (TT) 19210510.449383 ± 0.000308
perihelion distance 1.00845704 ± 0.00000145
eccentricity 1.00049609 ± 0.00003777
argument of perihelion [deg] 64.491010 ± 0.000236
longitude of the ascending node [deg] 269.440232 ± 0.000293
inclination [deg] 132.187612 ± 0.000113
inverse semimajor axis [10-6 au-1] -491.93 ± 37.46

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



data set of C/1921 E1

Figure caption: Six 2D-projections of the 6D space of original swarm (5001 VCs) of C/1921 E1. 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) 16240706
time of perihelion passage (TT) 19210510.690297 ± 0.000189
perihelion distance 1.00693074 ± 0.00000143
eccentricity 1.00012096 ± 0.00003788
argument of perihelion [deg] 64.705467 ± 0.000237
longitude of the ascending node [deg] 269.587562 ± 0.000307
inclination [deg] 132.180302 ± 0.000115
inverse semimajor axis [10-6 au-1] -120.12 ± 37.62

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.



data set of C/1921 E1

Figure caption: Six 2D-projections of the 6D space of future swarm (5001 VCs) of C/1921 E1. Each density map is given in logarithmic scale presented on the right in the individual panel.
The same figure in the new window

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

Epoch (TT) 22140224
time of perihelion passage (TT) 19210510.725714 ± 0.000333
perihelion distance 1.00362490 ± 0.00000145
eccentricity 1.00049067 ± 0.00003778
argument of perihelion [deg] 64.338847 ± 0.000239
longitude of the ascending node [deg] 269.351069 ± 0.000282
inclination [deg] 132.108442 ± 0.000123
inverse semimajor axis [10-6 au-1] -488.90 ± 37.64


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



Non–gravitational orbit


SSDP Cometary Note C1921E1N6-001

number of observations 568
number of residuals 914
data interval 1921 Mar. 15 — 1921 Nov. 26
rms [arcsec] 3.25
orbit quality class 2a

Osculating orbital elements (heliocentric; ecliptic J2000.0)

Epoch (TT) 19210421.0 = JD 2422800.5
time of perihelion passage (TT) 19210510.453240 ± 0.000810
perihelion distance 1.00843659 ± 0.00000434
eccentricity 1.00018145 ± 0.00007412
argument of perihelion [deg] 64.493716 ± 0.000563
longitude of the ascending node [deg] 269.438264 ± 0.000509
inclination [deg] 132.188366 ± 0.000185
inverse semimajor axis [10-6 au-1] -179.93 ± 73.50

Nongravitational parameters [10-8 au/day2] A1 = 3.155 ± 0.629 A2 = -0.451 ± 0.861 A3 = 0.0 (assumed)

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



data set of C/1921 E1

Figure caption: Six 2D-projections of the 6D space of original swarm (5001 VCs) of C/1921 E1. Each density map is given in logarithmic scale presented on the right in the individual panel.
The same figure in the new window

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

Epoch (TT) 16220319
time of perihelion passage (TT) 19210510.691603 ± 0.001631
perihelion distance 1.00687747 ± 0.00002269
eccentricity 0.99991349 ± 0.00008135
argument of perihelion [deg] 64.710041 ± 0.002463
longitude of the ascending node [deg] 269.585493 ± 0.000538
inclination [deg] 132.181074 ± 0.000188
inverse semimajor axis [10-6 au-1] 85.92 ± 80.79

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.



data set of C/1921 E1

Figure caption: Six 2D-projections of the 6D space of future swarm (5001 VCs) of C/1921 E1. Each density map is given in logarithmic scale presented on the right in the individual panel.
The same figure in the new window

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

Epoch (TT) 22170320
time of perihelion passage (TT) 19210510.725850 ± 0.001774
perihelion distance 1.00355226 ± 0.00002192
eccentricity 1.00021161 ± 0.00009695
argument of perihelion [deg] 64.332073 ± 0.002368
longitude of the ascending node [deg] 269.349172 ± 0.000497
inclination [deg] 132.109300 ± 0.000210
inverse semimajor axis [10-6 au-1] -210.87 ± 96.60


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





Solar System Dynamics & Planetology Group, 2014. All rights reserved

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