ABSTRACT

AST 0607505
Harris

Lightcurves provide fundamental information about asteroids: rotation periods, shape information, spin axis orientation, and surface light scattering properties through the photometric phase relation. Lightcurves have revealed the presence of binaries among asteroids and have allowed us to quantify the properties of these binary systems. As we probe to ever smaller asteroids, both Main-Belt Asteroids (MBAs) and Near-Earth Asteroids (NEAs), we find increasing numbers of very fast rotators, among which some are binaries, and very slow rotators, among which some, but not all, are "tumbling", that is, in states of non-principal axis rotation. The recently proposed radiation pressure alteration of asteroid spins (so-called YORP effect) offers an explanation for fast and slow rotations,
and also possibly binary formation and perhaps tumbling rotation states. In order to quantify this effect and place it in perspective with collisional evolution of spins, and for NEAs tidal alteration of spins or even disruption into binaries, more data are needed of the rotation states and/or binary configurations of the smallest MBAs accessible, as well as of more NEAs.

To advance these objectives, Dr. Harris and colleagues will coordinate observing campaigns concentrating on the smallest MBAs accessible, and on NEAs. These are coordinated programs involving about a dozen small observatories, mostly amateur facilities, but selected by their proven ability to take reliable and accurate observations. In addition to coordinating other observers, co-researcher Dr. Warner will observe approximately 50 asteroids per year, using the three telescopes
of the Palmer Divide Observatory. Collaborator Petr Pravec of Ondrejov Observatory in the Czech Republic, is coordinating a survey aimed to discover binaries among both small MBAs and NEAs. He and his co-workers at Ondrejov Observatory will observe a similar number of asteroids using the 0.65-m telescope and CCD camera there. Dr. Harris will coordinate these and other programs through a regular quarterly published column, email alert services, WWW support services, including posting lists of recommended and active targets, summaries of results, requests for observing help, an up-to-date list of all lightcurve results, and various observing guides and aids. Currently about 200 new lightcurve results a year are being reported. Survey campaigns of Hungarias and NEAs are currently yielding one or two newly discovered binaries per month.

This project has broad intellectual value as the currently most productive survey for binary asteroids. The lightcurve data files maintained draw frequent requests and citations from a broad range of observers and theoreticians as well. This project engages a large number of students and faculty of small colleges, as well as members of the general public (amateur astronomers), in important astronomical research. The NEA binary survey, for example, engages observers at eight small observatories around the U.S., two in Canada, and seven observatories in five other countries. In addition to routine contributions to the surveys, the work holds the prospect of making notable discoveries, namely satellites of asteroids. In the past 12 months alone, nearly a dozen binaries have
been discovered, most involving amateur or small college observatory participation. These discoveries are announced on IAU Circulars and publication in regular refereed journals.
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