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IAUC 6765: Sats OF URANUS

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                                                  Circular No. 6765
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)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html
Phone 617-495-7244/7440/7444 (for emergency use only)


SATELLITES OF URANUS
     Orbital computations by B. G. Marsden and G. V. Williams,
Harvard-Smithsonian Center for Astrophysics, suggest that the
observations of S/1997 U 2 (cf. IAUC 6764) are incompatible with a
heliocentric orbit and that the best-fitting uranicentric orbits are
quite eccentric, with a retrograde solution being significantly
preferable to a direct solution.  The poorer distribution of observations of
S/1997 U 1 renders this situation very much less conclusive.
Uranicentric orbital elements (referred to the ecliptic) and
ephemerides follow for S/1997 U 1 and S/1997 U 2, respectively, the
orbit for the former being arbitrarily adopted as retrograde and
the same size (a = 0.038356 AU, n = 0.86762 deg/day, P = 415 days)
as that for the latter.  Absolute magnitudes are H about 9.0 and 7.5,
respectively; for an albedo of 0.07, the radii of the objects would
be about 40 and 80 km.

     T = 1997 Feb.  7.812 TT          Peri. =  13.242
     e = 0.16014                      Node  = 182.292   2000.0
     q = 0.03221 AU                   Incl. = 137.845

1997 TT     R. A. (2000) Decl.     Delta     r_U   Elong. Phase      V
Oct.  9    20 29.43    -19 43.0   19.521    0.044  109.1    2.7     22.3
     19    20 29.37    -19 43.4   19.689    0.043   99.1    2.8     22.3
     29    20 29.65    -19 42.5   19.860    0.043   89.3    2.8     22.3
Nov.  8    20 30.28    -19 40.3   20.031    0.042   79.4    2.8     22.3
     18    20 31.24    -19 36.8   20.196    0.042   69.6    2.6     22.3
     28    20 32.51    -19 32.2   20.350    0.041   59.8    2.4     22.3
Dec.  8    20 34.06    -19 26.4   20.488    0.040   50.0    2.2     22.3

     T = 1998 Apr.  2.675 TT          Peri. = 232.919
     e = 0.52112                      Node  = 210.613   2000.0
     q = 0.01837 AU                   Incl. = 149.423

1997 TT     R. A. (2000) Decl.     Delta     r_U   Elong. Phase      V
Oct.  9    20 28.79    -19 37.6   19.440    0.057  108.9    2.8     20.7
     19    20 28.82    -19 37.2   19.607    0.057   99.0    2.9     20.7
     29    20 29.20    -19 35.6   19.778    0.056   89.2    2.9     20.7
Nov.  8    20 29.93    -19 32.8   19.950    0.055   79.3    2.8     20.8
     18    20 30.99    -19 28.8   20.116    0.053   69.5    2.7     20.8
     28    20 32.36    -19 23.8   20.273    0.052   59.8    2.5     20.8
Dec.  8    20 34.02    -19 17.8   20.416    0.050   50.0    2.2     20.8

                      (C) Copyright 1997 CBAT
1997 October 31                (6765)              Brian G. Marsden

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