We are going to get buzzed Tuesday. A reasonably large asteroid will pass quite close to the Earth, well inside lunar orbit. Asteroid 2005 YU55 will pass 325,000 km (202,000 mi) from the Earth. This is a good sized object, about 400m (1300ft) in diameter, large enough to create significant damage if it were to collide. We do know that the object will safely miss, this time. It is an object to track carefully. Data from this encounter and a future encounter with Venus in 2029 will set YU55 up for another encounter with Earth in 2041. Again we believe it will miss, but it will be close.
Keck 2 will be observing YU55 using adaptive optics and NIRC2 in an attempt to get high resolution imagery of the asteroid. It is quite convenient that this interesting asteroid is passing close to Earth, it will be in easy reach of our best astronomical instrumentation. I suspect I will be spending a little time in Keck 2 remote operations Tuesday night to get a look for myself.
For anyone trying to observe the asteroid with a small telescope, it will present a fair challenge. It will be well placed for observation on the evening of Nov. 8th, high in the sky in the constellation Pegasus. Finding it will require a small telescope as it estimated to be only about 11th magnitude. You will also need a precision ephemeris with coordinates every few minutes as it will be moving very quickly across the sky.
To get an accurate ephemeris requires use of software than can account for many different factors. With a close object you need to account for the observers position, simple geocentric calculations are not accurate enough. The NASA Horizons ephemeris generator is capable of doing the job. Below I have included an ephemeris for the night of Nov. 8th (Nov 9th UT) generated for Mauna Kea. This should be reasonably accurate for any place in the Hawaiian Islands. Times and dates are UT, so subtract 10 hours for HST, thus the table begins at 19:00HST (7pm)…
Date Time R.A. Dec. Az. El.
2011-Nov-09 05:00 m 23 09 05.55 +18 34 00.8 90.5601 71.3475
2011-Nov-09 05:15 m 23 14 12.25 +18 42 05.3 91.0621 73.6988
2011-Nov-09 05:30 m 23 19 07.78 +18 49 18.7 91.6712 76.0910
2011-Nov-09 05:45 m 23 23 52.49 +18 55 44.8 92.4456 78.5230
2011-Nov-09 06:00 m 23 28 26.72 +19 01 26.9 93.5106 80.9931
2011-Nov-09 06:15 m 23 32 50.83 +19 06 28.7 95.1903 83.4984
2011-Nov-09 06:30 m 23 37 05.18 +19 10 53.2 98.6524 86.0321
2011-Nov-09 06:45 m 23 41 10.15 +19 14 43.4 113.3075 88.5463
2011-Nov-09 07:00 t 23 45 06.11 +19 18 02.2 247.9758 88.6123
2011-Nov-09 07:15 m 23 48 53.43 +19 20 52.0 263.7716 86.0367
2011-Nov-09 07:30 m 23 52 32.47 +19 23 15.4 267.3929 83.3695
2011-Nov-09 07:45 m 23 56 03.58 +19 25 14.6 269.1848 80.6634
2011-Nov-09 08:00 m 23 59 27.12 +19 26 51.6 270.3734 77.9258
2011-Nov-09 08:15 m 00 02 43.43 +19 28 08.4 271.2946 75.1597
2011-Nov-09 08:30 m 00 05 52.83 +19 29 06.8 272.0779 72.3671
2011-Nov-09 08:45 m 00 08 55.63 +19 29 48.3 272.7837 69.5498
2011-Nov-09 09:00 m 00 11 52.15 +19 30 14.6 273.4441 66.7091
2011-Nov-09 09:15 m 00 14 42.68 +19 30 27.0 274.0781 63.8467
2011-Nov-09 09:30 m 00 17 27.50 +19 30 26.7 274.6973 60.9638
2011-Nov-09 09:45 m 00 20 06.87 +19 30 15.0 275.3097 58.0619
2011-Nov-09 10:00 m 00 22 41.06 +19 29 53.0 275.9210 55.1422
2011-Nov-09 10:15 m 00 25 10.31 +19 29 21.7 276.5354 52.2062
2011-Nov-09 10:30 m 00 27 34.85 +19 28 42.1 277.1563 49.2551
2011-Nov-09 10:45 m 00 29 54.91 +19 27 54.9 277.7864 46.2902
2011-Nov-09 11:00 m 00 32 10.69 +19 27 01.0 278.4283 43.3127
2011-Nov-09 11:15 m 00 34 22.40 +19 26 01.1 279.0842 40.3240
2011-Nov-09 11:30 m 00 36 30.23 +19 24 55.9 279.7563 37.3254
2011-Nov-09 11:45 m 00 38 34.35 +19 23 46.0 280.4466 34.3182
2011-Nov-09 12:00 m 00 40 34.94 +19 22 32.0 281.1575 31.3037
2011-Nov-09 12:15 m 00 42 32.16 +19 21 14.5 281.8911 28.2832
2011-Nov-09 12:30 m 00 44 26.16 +19 19 53.9 282.6497 25.2582
2011-Nov-09 12:45 m 00 46 17.08 +19 18 30.7 283.4360 22.2301
2011-Nov-09 13:00 m 00 48 05.06 +19 17 05.4 284.2526 19.2005
2011-Nov-09 13:15 m 00 49 50.22 +19 15 38.2 285.1026 16.1709
2011-Nov-09 13:30 m 00 51 32.69 +19 14 09.6 285.9891 13.1429
2011-Nov-09 13:45 m 00 53 12.58 +19 12 39.9 286.9158 10.1185
2011-Nov-09 14:00 m 00 54 50.00 +19 11 09.4 287.8867 7.0996
2011-Nov-09 14:15 m 00 56 25.04 +19 09 38.5 288.9062 4.0882
2011-Nov-09 14:30 m 00 57 57.80 +19 08 07.2 289.9792 1.0866
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