Presentiamo qui uno dei report inviati periodicamente dal GAT al
Central Bureau for Astronomical Telegrams,
INTERNATIONAL ASTRONOMICAL UNION. Per questo motivo il testo è in Inglese.
Sunward jets from Comet Hale-Bopp
Images of Comet Hale-Bopp were taken with 33,5 cm reflector
of SAS Observatory ( near Milano, Italy), equipped by a CCD
camera ( chip Thomson 7895 M) without any filter.
We applied Larson-Sekanina algoritm to elaborate some sets of
CCD pictures taken on May 28.00 U.T. (cumulative exposition
of 300 seconds ), on July 25.00 U.T., on July 30.9 U.T. and July
31.9 U.T. ( cumulative exposition of 600 seconds).
Together with a well defined antisolar tail more than 6' long, it
was surprising to observe almost three principal linear jets ( at
p.a.=40 , 145 and 270 ) and two other secondary jets coming
from the nuclear region toward solar direction too. The angolar
position of the jets seems costant during last week of July.
Images taken on August 16, show a great increase in the
number and complexity of sunward jets, but olso a clear
modification of the tail ( that now appears as dubble) (see very
well the last images inclosed).
On May 28 the jets were very faint. Now, at the end of July,
luminosity of tail and of linear jets don't appear very different.
The jets are linear up to 60"- 80" from the nucleus and don't
show any tendency to bend in fountain shape. This is quite
surprising if compared with a large number of fountain jets we
observed from Hyalutake nuclear region on March and April
'96, by the same equipment and after the same kind of
We interpret the difference between Hyakutake and Hale-Bopp
jets as linked to the different distance from the Sun. Probably,
Hale-Bopp is now so far from the sun ( 3.6 A.U.) that solar wind
is not able to bend its jets toward antisolar direction. Anyhow,
the discovery of so bright jets is an other clear indication that
Hale-Bopp is an intrinsecally bright comet.
Our Group is part of a Consortium between italian Institutes,
created by Prof. C.B.Cosmovici, to coordiante studies about
SL9, Hyakutake and Hale-Bopp comets.
We would appreciate very much any comments, suggestions
and information about some other similar observation.
Enclosed you can find some Hale-Bopp elaborated
pictures and a Hyakutake picture taken on March 28 (we
elaborated on the some way).