C/2007 JA21 LINEAR

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C/2007 JA₂₁ LINEAR

General description

2007 JA₂₁ was discovered on 11 May 2007 by the LINEAR as an apparently asteroidal object, and announced on MPEC2007-J52 (2007 May 12). Later, its cometary apperance was reported by several observers [IAUC 8837, 2007 May 13].

This comet made its closest approach to Earth on 26 May 2007 (5.211 au), six months after perihelion and two weeks after discovery.

Solution given below is based on data span over 1.3 yr in a range of heliocentric distances from 5.53 au to 7.14 au.

Comet suffered a 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 C2007JA_W-001

Comet C/2007 JA₂₁ LINEAR

number of observations	174
number of residuals	342
data interval	2007 May 11 — 2008 Aug. 27
rms [arcsec]	0.47
orbit quality class	1a

Osculating orbital elements (heliocentric; ecliptic J2000.0)

Epoch (TT)	20061101.0	= JD 2454040.5
time of perihelion passage (TT)	20061114.373398	± 0.003150
perihelion distance	5.36815179	± 0.00001740
eccentricity	1.00230714	± 0.00001092
argument of perihelion [deg]	93.697721	± 0.000388
longitude of the ascending node [deg]	65.522369	± 0.000030
inclination [deg]	89.840317	± 0.000022
inverse semimajor axis [10^-6 au^-1]	-429.78	± 2.03

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/2007 JA₂₁. 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)	17000419
time of perihelion passage (TT)	20061115.586363	± 0.003223
perihelion distance	5.36590022	± 0.00001785
eccentricity	0.99965064	± 0.00001073
argument of perihelion [deg]	93.783567	± 0.000393
longitude of the ascending node [deg]	65.483271	± 0.000030
inclination [deg]	89.879449	± 0.000022
inverse semimajor axis [10^-6 au^-1]	65.11	± 2.00

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)	23120630
time of perihelion passage (TT)	20061115.447846	± 0.003187
perihelion distance	5.36244677	± 0.00001766
eccentricity	1.00004874	± 0.00001072
argument of perihelion [deg]	93.664982	± 0.000396
longitude of the ascending node [deg]	65.497273	± 0.000030
inclination [deg]	89.861157	± 0.000022
inverse semimajor axis [10^-6 au^-1]	-9.09	± 2.00

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.