David Black	Lunar and Planetary Institute

SUBSTELLAR MASS OBJECTS: THE ZOO OF OBJECTS WITH MASS BELOW 80 
JUPITER MASSES

Two decades ago discussions of objects with masses below that required for
sustained nuclear burning of hydrogen into helium, a mass of roughly 80 times
the mass of Jupiter, or 0.08 times the mass of the Sun, were speculative and
theoretical.  The push to develop techniques and instrumentation that would
detect other planetary systems, as well as general development of infrared
detectors and large-aperture telescopes, has transformed the subject of
substellar mass objects (SMOs) into one that is beginning to be conducted in 
the glare of observational data.  We now have evidence from a wide variety of
observational techniques for the existence of SMOs as field objects, members
of clusters, and companions to both stars and fellow SMOs. The least massive
SMOs discovered to date have been detected with indirect detection methods,
most notably radial velocity surveys.  The more massive SMOs have been detected
by both indirect methods as well as by direct observation of radiation from the
SMOs.  The exciting challenge before us now, and the topic of the colloquium,
is to understand fully the nature of what has been referred to as a "zoo" of
SMOs, to sort out which of the SMOs belong in the "stellar" house, and 
which, if any, belong in the "planetary" house.  While doing this, we must be
willing to recognize that some of the newly discovered SMOs may indeed be of
neither species, but an altogether new type of animal in the celestial zoo.