Hello to all:
Many of you are aware that comet 45P is going to have
a close approach to Earth on August 15th 2011. At that
moment the comet will be at declination -70 degrees,
Delta= 0.06 AU which implies a scale of 43 km/second of
arc. It will then move rapidly to the north where it will
be observable in better conditions.
The secular light curve of this comet has been
published in the "Atlas of Secular Light Curves of Comets"
and it is available at

http://arxiv.org/ftp/arxiv/papers/0909/0909.3498.pdf

The diameter of this comet is 0.86+-0.37 km and its
photometric age, PAGE = 55+-3 comet years. According
to these numbers, this is a dwarf comet of middle age.

Two light curves are available, the log plot and the
time plot. They are useful for planning observations.
It is interesting to notice that the comet will turn on
70+-10 days before perihelion. Since perihelion takes
place on September 29th 2011, 70 days before corresponds
to July 20+-10 days. It is of great importance to try
to determine the turn on point of this comet with good
accuracy. The reason is that this comet is evolving
very rapidly and this evolution may show up in the turn
on distance. several revolutions will be need for this
detection so it is important to determine this number
accurately now.
At the turn on time the comet will be at declination
-22 deg and moving rapidly south toward its encounter with
Earth, so souther hemisphere observers are favoured.
I have calculated the amount of water that this
comet is loosing per revolution, and it is very
significant. If we convert that to a depth layer, it
looses 13 m per revolution. Since the radius is
only 430 m and assuming a constant depth removal, it
implies that the comet will sublimate away in only
33 revolutions, a very short time.
There is a great simmilarity between this comet and
the recently observed 103P/Hartley 2, and thus I would
like to predict that if high resolution observations
of the nucleus were made, it will show a cloud of large
debris surrounding the nucleus as for 103P.
Please make an effort to observe this comet at the
earliest opportunity and for as long as possible. When
the comet approaches Earth it will be extended in the sky
and it will be neccessary to use large phtometric appertures
to include all the coma. I have considered this issue in
the following paper:

http://www.webdelprofesor.ula.ve/ciencias/ferrin/teaching/curveofgrowth.pdf

I am interested in receiving your observations of this
comet. This is a worthwhile target coming near us soon.
Kind regards,

Ignacio Ferrin
University of Antioquia
Institute of Physics,
Medellin, Colombia
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