C/2002 T7 (LINEAR)
Discovered by LINEAR on 12 Oct 2002 and left on the NEOCP for the
unusually long time of 17 days before it was designated as a comet on
IAUC 8003, this was obviously an interesting object from the start. It
was due at perihelion 18 months later in Apr 2004 at a distance from the
Sun of only 0.62 AU.
The animation above is from the first images obtained at Great Shefford,
less than a week after discovery, when the comet was still 6.4AU from
Earth and 6.9AU from Sun and almost stellar in appearance. Even then it
was already mag +17.5, but moving very slowly due to its great distance
The image below, taken just over 1 year later is to the same scale as
the animation. By this time the comet was 1.8AU from Earth and 2.7AU from
Sun and the tail was pointing almost directly away from the Earth. The
central coma is entirely burnt out in the original CCD image and to show
the tail to best effect a High-Pass Fast Fourier Transform was performed
A further image 11 days later (to the same scale as the images above)
shows the rapidly changing geometry with the tail apparently swinging
round clockwise. Also indicated is how far the tail deviates from the
anti-solar direction. At this time the Earth was less that 6° from being
in the plane of the comet's orbit.
Note: The image has been processed by using a log 'stretch' to bring out
detail in both the fainter and brighter parts of the comet.
By December 17th the comet had just passed
its closest approach to Earth (1.56 AU on December 14th) and wouldn't be
as close to the Earth again until just before perihelion in April 2004. The tail was
pointing in a more normal anti-solar direction. The earth was just 2° from
the plane of the Comet's orbit.
Nearly four weeks later on January 11th 2004
and the comet's tail was lengthening (the original image showing the tail
at least 21' long, cut off at the edge of the frame). As the inner coma is
so heavily overexposed the inset is shown that reduces the glare of the
brightest parts while keeping the fainter detail.,
By early February 2004 a straight, thin ion
tail was visible in stark contrast to the diffuse and wide dust tail that
was still much in evidence.