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IAUC 8485: D/1819 W1

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                                                  Circular No. 8485
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)


COMET D/1819 W1 (BLANPAIN) AND 2003 WY25
     Already more than a year ago, S. Foglia, Milan, Italy,
reported a suggestion by M. Micheli that backward integration of
the orbit of 2003 WY25 given on MPEC 2003-Y78 (Catalina Sky Survey
discovery announcement on MPEC 2003-W41) suggested possible
identity -- though showing discordances extending up to 17 deg in
the argument of perihelion (Peri.) -- with the lost comet D/1819 W1
= 1819 IV, which was itself tentatively shown by H. B. Ridley (1957,
BAA Circ. No. 382) to be related to the one-time Phoenicid meteor
shower of 1956 Dec. 5.  P. Jenniskens, NASA Ames Research Center,
has now independently suggested the 1819-2003 identity with a Peri.
discordance of 0.2 deg.  Computations by B. G. Marsden, Harvard-
Smithsonian Center for Astrophysics, that included reexamination
of the 1819-1820 observations confirm a best-fit gravitational
linkage with Peri. discordance 0.2 deg.  He also showed that the
discordances in all three angular elements can be reduced to 0.01
deg by starting from the following orbital elements for 2003 WY25
(which had H = 21.1 and was consistently of stellar appearance
despite a passage only 0.025 AU from the earth on 2003 Dec. 12):

                    Epoch = 2003 Dec. 27.0 TT
     T = 2003 Dec. 11.5776 TT         Peri. =   9.0695
     e = 0.675583                     Node  =  69.3827  2000.0
     q = 1.000069 AU                  Incl. =   5.9292
       a =  3.082662 AU    n = 0.1821022    P =   5.412 years

Although backward integration of this orbit gives T too late in
1819, adjustment by Delta(T) = -4.28 days and modification of the
angular elements within the range indicated above yield the result

                    Epoch = 1819 Nov. 22.0 TT
     T = 1819 Nov. 20.27 TT           Peri. = 349.65
     e = 0.7028                       Node  =  80.02    2000.0
     q = 0.8893 AU                    Incl. =   9.23
       a =  2.9928 AU      n = 0.19036      P =   5.18 years

which satisfactorily represents 10 of the 13 observations made at
Paris, Bologna, and Milan during 1819 Dec. 14-1820 Jan. 15 within
90 arcsec.  The integrated orbital elements at the time of the
Phoenicid shower are T = 1956 Oct. 25.32 TT, Peri. = 0.14 deg, Node
= 74.37 deg, i = 9.60 deg (equinox 2000.0), q = 0.9914 AU, e =
0.6767, a = 3.0669 AU, P = 5.37 years.

                      (C) Copyright 2005 CBAT
2005 February 13               (8485)            Daniel W. E. Green

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