2003 UT55 (small Aten making close approach to Earth)
2003 UT55 was discovered by Jana Ticha, Milos Tichy and Michal Kocer
at the Klet Observatory with the 1.06-m telescope as part of their
ongoing KLENOT project. It was discovered on images taken at 22:42 UT on
26 Oct 2003 but trailed images were also found on frames taken up to 10
minutes beforehand. An animation
from the KLET observatory shows the rapid movement at discovery.
The object was posted on the NEO Confirmation Page at about 1am on 27
Oct 2003 with temporary designation NK0415 and was first noticed on the
NEOCP at Great Shefford at about 01:20 UT.
The original ephemeris indicated it was mag +17.1 and moving at
106"/minute (though this was subsequently updated to +17.0 and
103"/minute) but without any indication of the uncertainty area
that the object was likely to be found in.
The first search images from Great Shefford were taken at 01:24:40 UT,
but by then the altitude of the object was already just 32° and just
above the tree line to the southwest of the observatory. Within 15
minutes the field was partially obscured by the trees and by 01:50 UT
was out of sight. Sets of images were taken with exposures of 20 secs,
10 secs and 4 secs to try and locate the object but it was not located
on the images before the field had disappeared behind the trees.
The field of the first set of images taken to search for
NK0415 happened to catch the object very close to the right hand edge of
the frame. An enlarged area is shown to the right, with an animation of
the first three frames taken, showing the rapid movement of the object
and the change in brightness between frames. Each frame was a 10 second
exposure and the asteroid trailed by 17", or 5-6 pixels.
Subsequently a number of the frames were found to have faint images
of this fast moving asteroid and were measured and reported to the MPC.
The object was left on the NEOCP for a further three days as it raced
deep into the southern sky but no further positions were reported from
any other observatories. MPEC
2003-U96 was issued by the MPC at 02:30 UT on 30 Oct 2003 and
assigned NK0415 the provisional designation 2003 UT55.
2003 UT55 was shown to be an Aten type asteroid (having an orbital
period of less than 1 year), with a perihelion distance of 0.834 AU and
an aphelion distance of just 1.125 AU. With an absolute magnitude of
+27.3 it is estimated to be between 9 - 20 metres in diameter and passed
just 2.9 lunar distances from the Earth (or about 700,000 miles) at
06:56 UT on 27 Oct 2003 (JPL)
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