The Minor Planets Section

Minor Planets present a limitless opportunity and challenge for observers.  Any clear night features some minor planets favorably placed for observation, and the number observable approximately doubles for each 30% increase in aperture size.

With smaller telescopes asteroids are entirely star like in appearance.  Simply identifying them and tracking their motion across the star background hones good observing skills even for beginners.  The late Dr. J. U. Gunter wrote:  "Minor planet observing welds the observer, his telescope, and his charts into an efficiently functioning unit."

It is the goal of the Minor Planets Section to support all aspects of minor planet study and publish the findings in the quarterly Minor Planet Bulletin.

Several categories of useful minor planet research are in progress by members of the Minor Planets Section. Astrometric measures are nowadays performed with CCD cameras and automated measuring software with the results forwarded directly to the Minor Planet Center of the Smithsonian Astrophysical Observatory.  Members able to reach magnitude 17 and fainter with their equipment are discovering new minor planets, and with their discoveries accorded the right to recommend names.

Some of the most valuable research being performed by the Minor Planets Section is CCD photometry to obtain rotational lightcurves.  The best pioneering work is currently being done on minor planets in the  magnitude range 13 to 15.  It is strongly recommended that a series of lightcurves of the same minor planet be continued over an interval of several weeks or longer.  This extended observation interval is needed to derive accurate rotational parameters.  For an elongated minor planet rotating about its shortest axis the typical lightcurve contains two maxima and minima per rotation, and the interval between these determines the rotation period.  The difference between maximum and minimum light is an indicator of the amount of asymmetry between the axes.  In some cases one or three lightcurve maxima per rotation resulting from a more complex shape or surface albedo variations provides challenges to interpretation and additional lightcurves become especially desired.  When the rotation period is a simple fraction of the Earth's, observation at a single observatory cannot cover the complete lightcurve and fundamental rotation data become ambiguous.  For these cases the Minor Planets Section coordinates observers at widely varying longitudes to observe the same minor planet and thereby obtain among them the complete lightcurve.

Among the many thousands of catalogued minor planets there are inevitable errors in the published magnitudes.  Rotation and aspect variations complicate the determination of a single "average" value, but even beyond these some large discrepancies are being found.  This is a study to which visual as well as CCD observers are making important contributions.  The Minor Planet Section's Magnitude Alert Project (MAP) serves as a center for e-mail collection and rapid dissemination of magnitude discrepancies, which are checked by other cooperating observers. In the past few years Alerts have been sent for more than a hundred individual minor planets and definitive improvements have been obtained for many of these.

For any minor planet new observations are always welcome.  Even for the brighter, well-studied minor planets new observations further improve the accuracy of orbital and rotational parameters.  Previously unstudied or only briefly studied objects beckon without limit.  People interested in joining the fellowship of minor planet observers are welcomed to contact the Minor Planets Section Coordinator.