THE ASTRONOMER Electronic Circular No 678 1992 Oct 23 19.55UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke,
Hants, RG22 4PP,England. Telephone/FAX(0256)471074 Int:+44256471074
TELEX: 9312111261 Answerback: TA G TELECOM GOLD: 10074:MIK2885
GMH at UK.AC.RUTHERFORD.STARLINK.ASTROPHYSICS STARLINK: RLSAC::GMH
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PERIODIC COMET SWIFT-TUTTLE (1992t)
Orbital computations by Brian Marsden, and also by S. Nakano,
Sumoto, Japan, have so far failed to link all the observations,
even when allowance is made for nongravitational forces. Although
a reasonable fit can be made to the 1862 (except October) and 1992
observations, the resulting transverse nongravitational component
is so large that the resulting eighteenth-century perihelion time
is 15 months too late. Alternatively, although the three
perihelion times can be well represented without any consideration
of nongravitational forces at all, there are strong systematic
errors, amounting to more than 1', in 1862 and 1992. The
gravitational orbital elements below satisfy the observations in
1992 and in Oct. 1862 very well, and they also represent the
presumed 1737 perihelion time within 1 day. Backward computation of
this solution reveals few candidates for earlier appearances of the
comet, although the one of -68 fits within 1 year (there being 15
revolutions between then and 1862), and the comet of +60 may also
belong.
Future extrapolation gives the next return to perihelion as
2126 July 11, although the problem with the computation of the
nongravitational forces must introduce some uncertainty; a change
by +15 days could cause the comet to hit the earth on 2126 Aug. 14.
It therefore seems prudent to attempt to follow P/Swift-Tuttle for
as long as possible after the present perihelion passage, in the
hope that an adequate independent orbit determination,
uncontaminated by nongravitational effects, can be made from
mid-1993 (at r = 3 AU and far to the south) to, say, 1998 (when r
= 15 AU and an assumed nuclear absolute magnitude of 14 yields an
apparent magnitude of 26).
Epoch = 1992 Dec. 4.0 TT
T = 1992 Dec. 12.323 TT Peri. = 153.013
e = 0.96359 Node = 139.456 2000.0
q = 0.95812 AU Incl. = 113.430
a = 26.31666 AU n = 0.007301 P = 135.00 years
IAUC 5636
Extended ephemeris (cf E671) by G.Hurst using EPH.EXE by N.James:
m = 4.5 + 5.0 log R + 10.0 log r
Date R.A. (2000) Dec. R r Elong Mag. Motion
h m o ' (AU) (AU) o "/hr P.A.
1992 Oct
23.00 15 23.01 +52 37.4 1.277 1.276 67.0 6.1 234 120
24.00 15 31.81 +51 48.6 1.264 1.266 67.0 6.0 239 122
25.00 15 40.49 +50 56.7 1.251 1.255 66.8 6.0 243 123
26.00 15 49.03 +50 1.8 1.240 1.245 66.7 5.9 248 125
27.00 15 57.40 +49 3.8 1.229 1.235 66.5 5.9 252 126
28.00 16 5.61 +48 3.0 1.218 1.225 66.3 5.8 256 127
29.00 16 13.64 +46 59.3 1.209 1.215 66.1 5.8 260 129
30.00 16 21.48 +45 52.9 1.201 1.205 65.8 5.7 264 130
31.00 16 29.13 +44 43.9 1.193 1.195 65.6 5.7 267 131
1992 Nov
1.00 16 36.59 +43 32.5 1.186 1.186 65.2 5.6 270 132
2.00 16 43.84 +42 18.8 1.181 1.176 64.9 5.6 272 133
3.00 16 50.89 +41 3.0 1.176 1.167 64.5 5.5 275 134
4.00 16 57.74 +39 45.4 1.172 1.157 64.1 5.5 276 135
5.00 17 4.38 +38 26.0 1.169 1.148 63.6 5.4 278 136
6.00 17 10.83 +37 5.2 1.167 1.139 63.1 5.4 279 137
7.00 17 17.09 +35 43.1 1.165 1.130 62.6 5.4 279 138
Guy M Hurst