2006 CJ (Recovery at 2nd opposition)
2006 CJ was discovered on 1st Feb 2006 by Gordon Garradd at the
Siding Spring Observatory, at that time it was 20th magnitude and at a
declination of -21°. Over the next few weeks it brightened to +18th mag,
but remained at southerly declinations and was followed on another six
nights, being last reported on 14th Mar 2006.
It travels in a very elongated orbit taking it to within 0.17 AU of
the Sun at perihelion and just outside the Earth's orbit at 1.19 AU at
aphelion. With a period of just 6½ months, its orbit is smaller than
the Earth's and is therefore classed as an Aten type object. At
discovery it was just approaching aphelion, so was well placed in a dark
sky.
From the 7 week span of observations made at discovery, it was
predicted to make a close approach to the Earth around 1st Feb 2007.
Having passed through perihelion in early Dec 2006, by Feb 2007 it was
crossing the Earth's orbit, moving out towards aphelion at the end of
Mar 2007.
Hidden by the Sun's glare until just a few days from closest approach
on 1st Feb 2007 it would be heading swiftly north but it would only be
visible from Great Shefford 2 days later and by that time the
uncertainty in its position would be about ±1° with the object
anywhere on a line slightly South of East of the predicted place or
slightly North of West. At a predicted magnitude of about +16 and moving
at 23"/min (or the apparent diameter of the Moon in less than 1½
hours) it would be an easy object to search for and recover.
In an effort to recover 2006 CJ, images were taken on the evening of
3rd Feb 2007, starting at the nominal predicted place. The field of view
of the equipment at Great Shefford is about 18'x18' and the object was
not seen in those first images. Further fields towards the East were
then taken, with a 3' overlap, covering about half the uncertainty area
to the East but the object was not found. Fields to the West were then
taken and the object was recognised as soon as the first of these
westerly fields were being exposed
The animation below shows the fields taken during the search and
covers about half of the expected uncertainty area.
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