691028Planetary11_p1

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                 THE ROYAL ASTRONOMICAL SOCIETY OF CANADA

                                                                  Bulletin No. 11

                              PLANETARY SECTION

Summer has passed and now the Centres should be starting their programs again. We
hope these will include observing the planets.

MARS:   Drawings of this planet made during the recent apparition would be appreciated
as arrangements have been made to exchange observations with the Mars section of the
British Astronomical Association.

SATURN  is getting higher and higher in the evening sky and it is hoped our observers
will again don their parkas, mukluks and other paraphernalia and brave the elements!
Observing Saturn is very valuable as it is the amateur who keeps track of the surface
detail. (See Bulletin No.9 for observing hints.)

JUPITER should be having our attention, too, as it is observable in the morning sky for
early risers. Timings of Satellite Phenomena are very important, especially since the
Observatorto do Valongo in Brazil is depending on us.

A startling fact has been deduced from your observations, as is shown in the following
section. Comments and further observations are invited.

CALLISTO AND THE SOUTH EQUATORIAL BELT OF TUPITER

During the first half of 1969 much attention was given to Jupiter by the observers of the
Planetary Section. In response to these Bulletina several hundred drawings were sub-
mitted by Barry Sherman (Hamilton), D.R. Moore (Edmonton), Tom Tothill (Ottawa),
George Haeckel (Edmonton), John Garden (Hamilton), Richard Newman (Edmonton), John
Calder (Gait, Ontario), Paul Deans (Edmonton) and myself. A result of the analysis of
these drawings is that there appears to be a correlation between the intensity of the
South Equatorial Belt of Jupiter and the position of the satellite Callisto.

On certain drawings of the planet, the S.E ù B. was very dark. Sometimes It was shown
as being split into two dark components and, In other drawings It was either very faint
or missing altogether. The co-ordinator arranged these drawings in chronological order
with a view to determining when the Belt was visible and when it could not be seen.
It was amazing to discover that the Belt varied with a period of 16 days. This is very
nearly the orbital period of Callisto (16 days, 16 hours, 32 minutes) given in the
OBSERVER'S HANDBOOK.

The elongations of Callisto and the intensity estimates were formed into the diagram
which follows.  Each dot on the diagram indicates an observation. Lighter intensities
are at the bottom and darker ones at the top. The curve represents the position of
Callisto.

It can readily be seen that the Belt was darkest when Callisto was at Western elongation.
It was characteristic of the Belt to darken gradually, split, and then fade rapidly as the
elongation passed.

Is this a coincidence?  If so, it Is an amazing one!  It deserves the attention of all
members of the Section, professional and amateur alike.