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ESO Image Of Newly Discovered Comet C/1998 P1 Available


             Information from the European Southern Observatory

 ESO Press Photo 31/98

 12 August 1998                                                       [ESO]

 For immediate release

 http://www.eso.org/outreach/press-rel/pr-1998/phot-31-98.html
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First ESO Image of New Comet 1998 P1

A new comet was discovered on August 10 by amateur astronomer Peter Williams
of Heathcote (near Sydney, Australia). Having received information about
this, other observers on that continent sighted the new object yesterday,
August 11.

Official announcement of this discovery was sent yesterday evening to all
observatories by the IAU Central Bureau for Astronomical Telegrams on IAU
Circular no. 6986. The comet, provisionally designated as C/1998 P1, is seen
in the southern constellation Circinus (The Compass) and the magnitude is
estimated at about 9.5. This corresponds to about 25 times fainter than what
can be seen with the unaided eye. The comet is easily visible in small
telescopes. The orbit (and therefore the current distance) is not yet known.

Observations of the new comet were made with the 1.54-m Danish Telescope at
the ESO La Silla observatory, immediately in the evening of August 11. The
observers were Hans Kjeldsen (Theoretical Astrophysics Centre, University of
Aarhus, Denmark) and Hermann Boehnhardt (ESO La Silla, Chile).

  [ESO Press Photo 31/98 (Positive)]  ESO  [ESO Press Photo 31/98 (Negative)]  ESO
                                      Press                                    Press
                                      Photo                                    Photo
 31/98 (Positive)                         31/98 (Negative)
 [Preview - JPEG - 256k]                  [Preview - JPEG - 224k]
 [Full size - JPEG - 968k]                [Full size - JPEG - 816k]

The images shown here (in positive and negative) have been reproduced from a
2-min exposure with the DFOSC instrument through a B (blue) filter on August
11, at 23:40 UT.

The coma diameter is at least 6 arcmin and is almost spherical, with a
slight asymmetry on the tailside. A very thin and quite faint plasma-tail
points in the lower left direction (position angle = 1170 = "8 o'clock"),
which is most likely close to the radial direction opposite to the Sun (but
this can only be confirmed when a first orbit has been computed). The
visible plasma tail extends at least 6.5 arcmin (beyond the field of view)
and is produced by the emission of light from CO+ (carbon monoxide ions)
originating from sublimating ice of the cometary nucleus. The presence of
this tail indicates that the comet is probably less than 1.5 AU (about 225
million km) from the Sun.

At the time of the ESO observation, the comet was seen in the southern Milky
Way band. The sky field thus contains many background stars whose images are
somewhat trailed because the telescope was set to follow the motion of the
comet. Straylight (reflections in the telescope optics) from two bright
stars, one to the lower left of the comet and the other one just beyond the
lower left corner of the frame, cause bright extensions in the SSE - NNW
direction.

Technical information: 120-sec exposure through B-filtre with DFOSC on
Danish 1.54-m telescope. Only a few cosmetic corrections. The original frame
has 1911 x 1911 pixels which corresponds to 12.9 x 12.9 arcmin on the sky.
North is up, East to the left.

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This is the caption to ESO PR Photo 31/98. It is available in a positive and
a negative version. It may be reproduced, if credit is given to the European
Southern Observatory.

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            Copyright ESO Education & Public Relations Department
           Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany
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