Jewitt and Luu [1993] reported their discovery of
a slow-moving object (SMO), 1992 QB1, in a search covering 0.7
square degrees of sky to a limiting red magnitude of m
. The distance of the object from the Sun, R, is derived from
its angular motion. Astrometric observations over
a 4 month period yielded a heliocentric distance R
Astronomical Units (AU, the distance from the Earth to the Sun, 
m). Assuming a low albedo, 0.04, consistent with
current perceptions of outer solar system objects, a diameter of
km is suggested, given its manitude of 
.
This is 1/8th the diameter of Pluto. The object, which has not
yet received an official name from the International Astronomical
Union, has broad-band colors significantly redder than the Sun,
implying a compositional model of dirty ice or organic-rich
composition. Its colors are not consistent with pure ice.
From examination of the surface brightness profile, there is no
signal in excess of the point spread function and thus no evidence
of a dust coma. An upper limit for mass loss of 
kg
s
is obtained using Luu and Jewitt's [1992]
model. This is a factor of 104 times less active than was comet
P/Halley at perihelion. The position and orbital elements of this
object suggest that it might be a member of the hypothesized Kuiper
Belt [ Levison and Duncan, 1993], though the
diameter of short-period comets are of the order of 10's of
kilometers, not hundreds as implied by the diameter estimates of
this population.
As of this writing, 16 additional trans-Neptunian objects have been found. Their designations and orbital elements are listed in Table 1. The discovery of these objects leads us to recognize that our inventory of small solar system bodies is far from complete. With the availability of large telescopes and the diligence of observers, it has been possible to test the hypotheses of dynamical models that predict the existence of a belt of objects producing the short period comets. The discovery of these objects poses immediate questions. How many objects reside in this population, what are their basic physical properties, their size, color, shape, and composition? Are they the source of short period comets and if so, what mechanisms control their evolving orbits? A summary of the available answers to these questions is presented by Luu [1994].