Subj: [Fwd: AstroAlert: Fast-mover 2000 UG11]
Date: 10/29/00 7:45:38 PM Pacific Standard Time

Minor Planet AstroAlert: 2000 UG11

On October 25, 2000 (Universal Time), Lincoln Laboratory's 1.0-meter
LINEAR robotic telescope in New Mexico, operated by M. Blythe, F.
Shelly, and colleagues, captured five images of a 17th-magnitude
object only a few degrees east of the galaxy M33 in Triangulum.
Later, more LINEAR images from October 21st were identified with
the same object. Gareth V. Williams posted details of the find on
the Minor Planet Center's Web site to alert astrometric observers
around the world ( http://cfa-www.harvard.edu/iau/mpc.html ).

Additional astrometric observations were quickly obtained, including
three by Larry Robinson (Sunflower Observatory, Kansas, 10-inch
Schmidt-Cassegrain) and two by Bill Yeung (Desert Beaver Observatory,
Arizona, 18-inch Newtonian). Based on a total of 35 positions,
Timothy B. Spahr of the Minor Planet Center issued the first
electronic circular on the new object last night and assigned it
the temporary designation 2000 UG11.

Unlike most such objects (several of which are currently being
discovered weekly), 2000 UG11 is brightening rapidly. It should
reach 14th magnitude in the first week of November as it
passes only about six Earth-Moon distances from our planet on
the night of November 7-8. Spahr's second preliminary orbit,
issued today on Minor Planet Electronic Circular E2000-U31, is
as follows:

Epoch 2000 Sept. 13.0 TT
Mean anomaly, M 324.78505
Semimajor axis, a 1.9343152
Eccentricity, e 0.5727494
Arg. of perihelion 240.15459
Long. of ascending node 224.43165 (equinox 2000.0)
Inclination, i 8.94449

These elements show that 2000 UG11 completes a revolution around
the Sun every 2.7 years, ranging from as far out as 3.0 astro-
nomical units (beyond the orbit of Mars) to as close as 0.8 a.u.
(well inside Earth's orbit). Spahr has assigned it a PHA
(Potentially Hazardous Object) rating of 0.005, meaning that it
bears watching as a possible threat to Earth at some point in
the future.

During the few days leading up to the flyby on November 8th,
2000 UG11 will brighten to about magnitude 13.6 as it races
southeastward just north of the Pleiades. On the evening of
November 6th, it will be moving more than 1 degree per hour!
By the 10th, however, as it shifts to the sunward side of Earth,
it will have faded back to magnitude 17 or fainter. The window
for determining an accurate orbit is thus very short, and
observers should put this object high on their list of
astrometric targets during the next two weeks or so.

The following ephemeris, calculated from Spahr's orbital elements,
gives the object's right ascension and declination at 6-hour
intervals. Also listed is its distance from the Earth (Delta) and
the Sun (r) in a.u., expected visual magnitude, and the constel-
lation through which it is passing. When searching for the asteroid,
keep in mind the parallax effect. Because this object is so close
to the Earth around the 8th, it can appear displaced up to about
9 arcminutes from the geocentric positions tabulated below.


Roger W. Sinnott

Associate Editor
Sky & Telescope


-------------------------------------------------------------

Ephemeris for Minor Planet 2000 UG11

Date UT R.A. (2000) Decl. Delta r V Const.
Oct 28 0h 2 06.6 +30 57 0.092 1.082 16.6 Tri
Oct 28 6h 2 07.7 +30 56 0.090 1.080 16.5 Tri
Oct 28 12h 2 08.7 +30 55 0.088 1.078 16.5 Tri
Oct 28 18h 2 09.9 +30 54 0.086 1.076 16.4 Tri
Oct 29 0h 2 11.0 +30 53 0.084 1.074 16.3 Tri
Oct 29 6h 2 12.3 +30 51 0.082 1.072 16.3 Tri
Oct 29 12h 2 13.6 +30 50 0.080 1.070 16.2 Tri
Oct 29 18h 2 15.0 +30 48 0.078 1.068 16.2 Tri
Oct 30 0h 2 16.4 +30 46 0.076 1.066 16.1 Tri
Oct 30 6h 2 18.0 +30 44 0.074 1.064 16.0 Tri
Oct 30 12h 2 19.6 +30 42 0.072 1.062 16.0 Tri
Oct 30 18h 2 21.3 +30 39 0.070 1.060 15.9 Tri
Oct 31 0h 2 23.1 +30 36 0.068 1.058 15.8 Tri
Oct 31 6h 2 25.0 +30 32 0.065 1.056 15.7 Tri
Oct 31 12h 2 27.1 +30 29 0.063 1.054 15.7 Tri
Oct 31 18h 2 29.3 +30 25 0.061 1.052 15.6 Tri
Nov 01 0h 2 31.6 +30 20 0.059 1.050 15.5 Tri
Nov 01 6h 2 34.1 +30 15 0.057 1.048 15.4 Ari
Nov 01 12h 2 36.7 +30 09 0.055 1.046 15.3 Ari
Nov 01 18h 2 39.6 +30 03 0.053 1.044 15.3 Ari
Nov 02 0h 2 42.6 +29 55 0.052 1.042 15.2 Ari
Nov 02 6h 2 45.9 +29 47 0.050 1.040 15.1 Ari
Nov 02 12h 2 49.4 +29 38 0.048 1.038 15.0 Ari
Nov 02 18h 2 53.3 +29 28 0.046 1.036 14.9 Ari
Nov 03 0h 2 57.4 +29 16 0.044 1.034 14.8 Ari
Nov 03 6h 3 02.0 +29 02 0.042 1.032 14.7 Ari
Nov 03 12h 3 06.9 +28 46 0.040 1.030 14.6 Ari
Nov 03 18h 3 12.3 +28 28 0.038 1.028 14.5 Ari
Nov 04 0h 3 18.2 +28 08 0.036 1.026 14.4 Ari
Nov 04 6h 3 24.8 +27 44 0.034 1.025 14.3 Ari
Nov 04 12h 3 32.0 +27 15 0.032 1.023 14.2 Tau
Nov 04 18h 3 39.9 +26 42 0.031 1.021 14.1 Tau
Nov 05 0h 3 48.8 +26 03 0.029 1.019 14.0 Tau
Nov 05 6h 3 58.6 +25 16 0.027 1.017 13.9 Tau
Nov 05 12h 4 09.6 +24 20 0.026 1.015 13.8 Tau
Nov 05 18h 4 21.8 +23 14 0.024 1.013 13.7 Tau
Nov 06 0h 4 35.5 +21 53 0.022 1.011 13.7 Tau
Nov 06 6h 4 50.7 +20 17 0.021 1.009 13.6 Tau
Nov 06 12h 5 07.7 +18 21 0.020 1.008 13.6 Tau
Nov 06 18h 5 26.5 +16 03 0.019 1.006 13.6 Ori
Nov 07 0h 5 47.1 +13 21 0.018 1.004 13.6 Tau
Nov 07 6h 6 09.4 +10 15 0.017 1.002 13.6 Ori
Nov 07 12h 6 33.1 +06 45 0.016 1.000 13.7 Mon
Nov 07 18h 6 57.9 +02 59 0.016 0.998 13.9 Mon
Nov 08 0h 7 23.2 -00 56 0.016 0.997 14.1 Mon
Nov 08 6h 7 48.5 -04 50 0.016 0.995 14.3 Mon
Nov 08 12h 8 13.1 -08 31 0.016 0.993 14.6 Hya
Nov 08 18h 8 36.5 -11 52 0.017 0.991 14.9 Hya
Nov 09 0h 8 58.4 -14 50 0.018 0.989 15.3 Hya
Nov 09 6h 9 18.5 -17 23 0.019 0.987 15.6 Hya
Nov 09 12h 9 36.8 -19 32 0.020 0.986 16.0 Hya
Nov 09 18h 9 53.3 -21 19 0.021 0.984 16.3 Hya
Nov 10 0h 10 08.2 -22 49 0.023 0.982 16.6 Hya
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