MPEC 1998-Y28 : 1996 TR66
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M.P.E.C. 1998-Y28 Issued 1998 Dec. 24, 16:06 UT
The Minor Planet Electronic Circulars contain information on unusual
minor planets and routine data on comets. They are published
on behalf of Commission 20 of the International Astronomical Union by the
Minor Planet Center, Smithsonian Astrophysical Observatory,
Cambridge, MA 02138, U.S.A.
BMARSDEN@CFA.HARVARD.EDU or GWILLIAMS@CFA.HARVARD.EDU
URL http://cfa-www.harvard.edu/iau/mpc.html
1996 TR66
Revision to MPEC 1997-S13
Observations:
J96T66R C1998 11 15.31809 00 10 15.40 +06 35 33.5 22.6 R 568
J96T66R C1998 11 15.33171 00 10 15.35 +06 35 33.0 22.6 R 568
J96T66R C1998 11 22.33160 00 09 56.75 +06 33 06.2 22.6 R 568
J96T66R C1998 11 23.27500 00 09 54.61 +06 32 48.4 22.6 R 568
Observer details:
568 Mauna Kea. Observer D. Jewitt. Measurer C. Trujillo. 10-m Keck
reflector + CCD, 2.2-m University of Hawaii reflector + CCD.
First and last observations above in comparison with prediction:
Residuals in seconds of arc and reference
981115 568 94.6- 90.9- 981123 568 88.3- 87.7- MPC 30765
Orbital elements:
1996 TR66
Epoch 1999 Jan. 22.0 TT = JDT 2451200.5 Marsden
M 33.90737 (2000.0) P Q
n 0.00293709 Peri. 310.55738 +0.40464448 +0.91231717
a 48.2900279 Node 342.98757 -0.76073939 +0.29773219
e 0.4006295 Incl. 12.38880 -0.50748244 +0.28112795
P 336 H 7.4 G 0.15
Residuals in seconds of arc
961008 568 1.4- 0.5- 961012 568 0.8+ 0.7+ 981115 568 0.1+ 0.2+
961008 568 0.4- 0.3- 970905 675 0.5+ 0.5- 981115 568 0.0 0.0
961008 568 0.7- 0.1+ 970905 675 0.2+ 0.6- 981122 568 0.4- 0.2+
961012 568 0.6+ 0.6+ 970906 675 0.2+ 0.4- 981123 568 0.2- 0.4+
961012 568 0.5+ 0.4+ 970906 675 0.1+ 0.3-
Ephemeris:
1996 TR66 a,e,i = 48.29, 0.40, 12 q = 28.944
Date TT R. A. (2000) Decl. Delta r Elong. Phase V
1998 12 23 00 09.54 +06 27.8 36.268 36.346 93.8 1.5 23.2
1999 01 02 00 09.76 +06 28.3 36.452 36.357 83.7 1.5 23.2
1999 01 12 00 10.15 +06 29.9 36.632 36.367 73.6 1.5 23.2
1999 01 22 00 10.71 +06 32.7 36.804 36.377 63.6 1.4 23.2
1999 02 01 00 11.41 +06 36.6 36.962 36.388 53.7 1.3 23.2
1999 02 11 00 12.24 +06 41.5 37.103 36.398 43.9 1.1 23.2
1999 02 21 00 13.19 +06 47.2 37.223 36.409 34.1 0.9 23.2
This TNO appears to be, not the 2:3 Neptune librator suggested on
MPEC 1997-N10 from observations on the two nights (four days apart) in 1996,
nor the possible case of a second 3:5 Neptune librator suggested on MPEC
1997-S13 on combination with observations on two consecutive nights in 1997,
but the second case--probably now fully demonstrated--of a 1:2 Neptune
librator, companion to 1997 SZ10 (MPEC 1998-Y09)! The general solution
from the six nights (two in each year) of observation gives a = 47.5 AU,
e = 0.38, i = 12 deg (epoch 1999 Jan. 22), which--unlike the 1997 SZ10
solution--is not close enough to the 1:2 resonance to prevent near-collisions
with Neptune within a matter of millennia. The assumed orbit above fits
the observations in a marginally worse manner but keeps the object more
than 27.7 AU from Neptune within 7000 years of the present (symmetrically
in the past and future). The minimum distance from Uranus is 9.7 AU. In
like manner, an orbit for 1997 SZ10 with a = 48.39 AU, e = 0.367, i = 11.8
deg (epoch 1999 Jan. 22) also symmetricizes the distance from Neptune at
more than 25 AU. Since the relative frequency of 2:3 and 1:2 librators
is a matter of some importance for models of the TNO system (Malhotra 1995,
Astron. J. 110, 420), further astrometric observations of both 1996 TR66
and 1997 SZ10 are desirable, particularly at the 1999 and 2000 oppositions.
Brian G. Marsden (C) Copyright 1998 MPC M.P.E.C. 1998-Y28
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