MPEC 2002-A70 : 2001 XP254, 2001 XQ254, 2001 XR254
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M.P.E.C. 2002-A70 Issued 2002 Jan. 12, 17:55 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.
Prepared using the Tamkin Foundation Computer Network
MPC@CFA.HARVARD.EDU
URL http://cfa-www.harvard.edu/iau/mpc.html ISSN 1523-6714
2001 XP254, 2001 XQ254, 2001 XR254
Observations:
K01XP4P* C2001 12 10.41353 06 42 43.04 +24 14 47.1 568
K01XP4P C2001 12 10.43941 06 42 42.89 +24 14 47.5 568
K01XP4P C2001 12 10.46266 06 42 42.74 +24 14 47.6 568
K01XP4P C2002 01 08.56257 06 39 36.04 +24 17 31.9 22.5 R 568
K01XP4P C2002 01 08.59063 06 39 35.84 +24 17 32.2 22.5 R 568
K01XP4Q* C2001 12 10.50297 06 45 54.63 +22 05 16.1 568
K01XP4Q C2001 12 10.52777 06 45 54.49 +22 05 16.4 568
K01XP4Q C2001 12 10.55144 06 45 54.33 +22 05 16.6 568
K01XP4Q C2002 01 08.51228 06 42 44.92 +22 09 59.3 22.2 R 568
K01XP4Q C2002 01 08.53796 06 42 44.74 +22 09 59.5 22.5 R 568
K01XP4R* C2001 12 10.57795 06 48 46.70 +21 43 31.0 568
K01XP4R C2001 12 10.60115 06 48 46.60 +21 43 31.0 568
K01XP4R C2001 12 10.62681 06 48 46.46 +21 43 31.1 568
K01XP4R C2002 01 08.52922 06 46 22.74 +21 46 10.5 21.6 R 568
K01XP4R C2002 01 08.55399 06 46 22.62 +21 46 10.6 21.6 R 568
Observer details:
568 Mauna Kea. Observers D. C. Jewitt, S. S. Sheppard, J. Kleyna. Measurer
S. S. Sheppard. 3.6-m Canada-France-Hawaii Telescope and 2.2-m University
of Hawaii reflector + CCD.
Orbital elements:
Object H G Epoch M Peri. Node Incl. e a Arc C
K01XP4P 7.7 0.15 K01CH 0.015 151.146 307.939 2.352 0.42414 57.16818 29EX
K01XP4Q 7.8 0.15 K01CH 0.016 352.619 107.277 7.040 0.42883 55.17448 29EX
K01XP4R 5.5 0.15 K01CH 0.067 280.034 180.744 1.230 0.0 44.15276 29EX
Ephemerides:
2001 XP254 a,e,i = 57.17, 0.42, 2 q = 32.921
Date TT R. A. (2000) Decl. Delta r Elong. Phase V
2002 01 06 06 39.88 +24 17.3 31.943 32.921 173.5 0.2 22.9
2002 01 16 06 38.81 +24 18.1 31.978 32.921 163.1 0.5 22.9
2002 01 26 06 37.82 +24 18.7 32.042 32.921 152.8 0.8 22.9
2002 02 05 06 36.94 +24 19.2 32.134 32.921 142.4 1.0 23.0
2002 02 15 06 36.21 +24 19.4 32.250 32.921 132.1 1.3 23.0
2002 02 25 06 35.66 +24 19.4 32.387 32.921 121.9 1.5 23.0
2002 03 07 06 35.31 +24 19.3 32.539 32.921 111.8 1.6 23.1
2002 03 17 06 35.18 +24 18.9 32.703 32.921 101.8 1.7 23.1
2002 03 27 06 35.27 +24 18.4 32.873 32.921 91.9 1.7 23.1
2002 04 06 06 35.59 +24 17.6 33.044 32.921 82.1 1.7 23.1
2002 04 16 06 36.12 +24 16.7 33.211 32.922 72.4 1.7 23.1
2002 04 26 06 36.86 +24 15.6 33.369 32.922 62.8 1.6 23.1
2002 05 06 06 37.79 +24 14.4 33.514 32.922 53.3 1.4 23.1
2002 05 16 06 38.88 +24 13.0 33.643 32.922 43.9 1.2 23.1
2002 05 26 06 40.12 +24 11.5 33.751 32.922 34.6 1.0 23.1
2001 XQ254 a,e,i = 55.17, 0.43, 7 q = 31.514
Date TT R. A. (2000) Decl. Delta r Elong. Phase V
2002 01 06 06 43.03 +22 09.6 30.535 31.514 174.4 0.2 22.8
2002 01 16 06 41.94 +22 11.2 30.567 31.514 164.0 0.5 22.8
2002 01 26 06 40.92 +22 12.9 30.629 31.514 153.6 0.8 22.9
2002 02 05 06 40.01 +22 14.4 30.719 31.514 143.3 1.1 22.9
2002 02 15 06 39.26 +22 15.8 30.833 31.514 133.0 1.3 22.9
2002 02 25 06 38.68 +22 17.1 30.968 31.514 122.8 1.5 22.9
2002 03 07 06 38.32 +22 18.2 31.119 31.515 112.6 1.7 23.0
2002 03 17 06 38.17 +22 19.0 31.282 31.515 102.6 1.8 23.0
2002 03 27 06 38.26 +22 19.7 31.452 31.515 92.7 1.8 23.0
2002 04 06 06 38.58 +22 20.2 31.623 31.515 82.9 1.8 23.0
2002 04 16 06 39.12 +22 20.4 31.790 31.515 73.2 1.7 23.0
2002 04 26 06 39.87 +22 20.4 31.949 31.515 63.6 1.6 23.0
2002 05 06 06 40.82 +22 20.2 32.095 31.515 54.2 1.5 23.0
2002 05 16 06 41.94 +22 19.7 32.226 31.516 44.8 1.3 23.0
2002 05 26 06 43.21 +22 19.1 32.336 31.516 35.4 1.1 23.0
2001 XR254 a,e,i = 44.15, 0.00, 1
Date TT R. A. (2000) Decl. Delta r Elong. Phase V
2002 01 06 06 46.59 +21 45.9 43.173 44.153 175.2 0.1 21.9
2002 01 16 06 45.76 +21 46.9 43.202 44.153 164.9 0.3 22.0
2002 01 26 06 44.97 +21 47.9 43.262 44.153 154.6 0.5 22.0
2002 02 05 06 44.26 +21 48.8 43.349 44.153 144.3 0.7 22.0
2002 02 15 06 43.66 +21 49.6 43.461 44.153 134.0 0.9 22.1
2002 02 25 06 43.18 +21 50.4 43.594 44.153 123.8 1.1 22.1
2002 03 07 06 42.84 +21 51.0 43.744 44.153 113.7 1.2 22.1
2002 03 17 06 42.67 +21 51.4 43.907 44.153 103.7 1.3 22.1
2002 03 27 06 42.65 +21 51.8 44.076 44.153 93.8 1.3 22.1
2002 04 06 06 42.80 +21 51.9 44.247 44.153 83.9 1.3 22.1
2002 04 16 06 43.11 +21 51.9 44.416 44.153 74.2 1.3 22.1
2002 04 26 06 43.57 +21 51.6 44.576 44.153 64.5 1.2 22.1
2002 05 06 06 44.18 +21 51.2 44.724 44.153 55.0 1.1 22.1
2002 05 16 06 44.91 +21 50.7 44.856 44.153 45.5 0.9 22.1
2002 05 26 06 45.75 +21 49.9 44.968 44.153 36.1 0.8 22.1
While it is of course impossible to "determine" the orbit of a
transneptunian object from observations on only two nights, or indeed, from
observations on several nights over a span of only a month or two, the
orbital elements supplied with a TNO discovery announcement in these Circulars
are intended to be an educated guess. If, as for 2001 XR254, there exists a
satisfactory direct, circular solution with radius in the "cubewano" range of
42-47 AU, this is the solution that is usually adopted. If the circular
solution has a radius a little outside this range, the orbit adopted might
be based on a low-eccentricity Vaisala solution (perihelic or aphelic, even
though real discoveries near aphelion seem to be quite rare) with semimajor
axis inside the range. If a circular solution puts the object significantly
closer to Neptune's orbit, the likely choice made for the TNO's orbit would
be of plutino-type, frequently (though not necessarily) at perihelion, with
a check made that the 2:3 resonance does in fact prevent the object from
actually approaching Neptune over some rather considerable time interval.
Although the current heliocentric distances could suggest plutino status for
2001 XP254 and XQ254, their angular elongations from Neptune argue against
this, and for these cases it is not unreasonable, as here, to place the
objects at the perihelia of much more eccentric, scattered-disk-type
solutions. In a similar vein, a nonperihelic scattered-disk-type solution
could be logical to adopt for an object unlikely to be a cubewano near
aphelion or impossible to be a plutino near aphelion. Of course, when the
possible solutions preclude the most common cases, a wealth of rarer
possibilities exists, including solutions librating at the 3:4 and 1:2
resonances with Neptune, nearly circular solutions between the 3:4 and 2:3
resonances, centaur-type solutions near aphelion and--perhaps most
surprisingly--eccentric solutions with perihelia at cubewano distances.
It can of course be argued that it may be inappropriate to adopt a
particular solution along these lines because, after all, a very large
range of solutions (including retrograde and hyperbolic orbits) will
mathematically represent the available observations. The MPC has in fact
been criticized for not specifically indicating this uncertainty--in either
the orbital elements or, more importantly, the tabulated ephemeris.
The counter argument to this is that the whole purpose of the MPEC
announcement is to encourage further observations, and if the announcement
is made (as it should be) relatively soon after the last available
observation, any ephemeris should be good enough to locate the object
within some further reasonable time, success then allowing the orbit
computation to be improved. The problem is, of course, that the objects
reported are usually very faint, and time on the telescopes necessary to
observe them is at a premium. Further observations may in fact not be
attempted until the following opposition, by which time the sky-position
uncertainty can be enormous in comparison with the telescope field. In order
to address this problem, sky-position uncertainty maps for one-opposition
transneptunian objects are now routinely available in the MPC's WWW Minor
Planet Ephemeris Service (http://cfa-www.harvard.edu/iau/MPEph/MPEph.html),
as an extension to the service that has existed for many NEOs for some time
(notably in the NEO Confirmation Page for single-night detections of new NEO
candidates). Of course, the mathematical uncertainty can be much larger
than the likely physical uncertainty, so it is recommended that the maps
be used to search progressively outward from the center of the plot, which
corresponds to the position defined by the adopted orbit solution. The plots
can be generated for dates that are many years after (or before) the objects
were observed, and under such circumstances they may contain additional
branches that are quite separated from where the objects are at all likely
to be. As noted on the Ephemeris Service webpage, there will usually be some
delay, possibly several hours, between the announcement of a new object on an
MPEC and the availability of the WWW ephemeris and uncertainty map.
Brian G. Marsden (C) Copyright 2002 MPC M.P.E.C. 2002-A70
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