2005 AH and 2005 AJ (13th & 14th discoveries made at Great Shefford)
Discovery field of 2005 AH and 2005 AJ on 04/05 Jan 2005.
Galaxy UGC 3751 (mag +14.8) is to the west of 05312 and an anonymous mag
+17 galaxy is west of 2005 AJ.
Note there are several internal reflections at the bottom right of the
image.
Apollo asteroid 2004 XG29 had been discovered approaching
Earth in Pisces on 2004 Dec 10 by
LINEAR at mag +19.3, moving at 24"/min. It was followed through its close approach
(to within 5.9 Lunar Distances of the Earth on Dec 12th) by which time
it was mag +18.5 and moving at 30"/min. and last spotted on Dec 18th
at mag +18.0 and still moving at 11"/min in eastern Taurus before
the Moon interrupted viewing at the end of the month.
On the night of Jan 4/5 2005 and with the Moon out of the way again, 2004
XG29 was listed by the Minor Planet Center as mag +20.6
moving much slower at 0.7"/min and fading fast, positioned about
1.5° NW of Delta Geminorum in a rich Milky Way field. It hadn't been
reported for over two weeks. In an attempt to record it a series of 99
30-second exposures were taken and digitally combined into three stacks
of approx. 30 images each. As well as revealing 2004 XG29
there were also some other bright moving objects easily noticed within
the field.
After measuring positions for 2004 XG29, Astrometrica was
then used to identify other known minor planets in the field using its
'Known Objects Overlay' tool and also to re-stack the images for the
motion of these main belt minor planets, all of which were moving in
almost the exact opposite direction to the Apollo asteroid 2004 XG29.
When the three stacks were again blinked to reveal moving objects, as
well as four identified main belt minor planets, two unidentified
objects with similar motion (and therefore very likely to be main belt
objects as well) were noticed. Positions were measured, the two objects
assigned temporary designations and the details sent off to the Minor
Planet Center (MPC) by 03:07UT on 5th Jan.
Fortunately the following night was clear and follow-up on both
objects could be done. Positions were sent off to the MPC by 23:21 UT on
5th Jan and half an hour later an e-mail was received back from the MPC
giving their new provisional designations of 2005 AH and 2005 AJ.
2005 AH had been reported back in Dec 2004 by both the Catalina Sky
Survey (Dec 9th) and by Spacewatch at Kitt Peak (Dec 16th) but the two
sets of positions were not linked at that time and no designation was
issued.
2005 AJ had also been reported the previous month, this time on just
one night by Spacewatch on Dec 16th.
With an additional set of positions for 2005 AJ obtained from Great
Shefford on Jan 13th both objects had orbits published based on
observations spanning about four weeks. 2005 AH has a moderately
eccentric orbit, taking it from 2.0 AU when closest to the Sun to 3.2 AU
at its furthest. It was about 8 months past perihelion when discovered,
at a distance of 2.4 AU. 2005 AJ is in a nearly circular orbit only
varying from 2.7 - 2.9 AU from the Sun. Both objects are in low
inclination orbits.
|
