  The low-inclination component of the Classical Kuiper Belt is host to a
population of extremely widely-separated binaries. These systems are similar to
other Trans-Neptunian binaries (TNBs) in that the primary and secondary
components of each system are of roughly equal size. We have performed an
astrometric monitoring campaign of a sample of seven wide-separation,
long-period TNBs and present the first-ever well-characterized mutual orbits
for each system. The sample contains the most eccentric (2006 CH69, e=0.9) and
the most widely-separated, weakly bound (2001 QW322, a/Rh~0.22) binary minor
planets known, and also contains the system with lowest-measured mass of any
TNB (2000 CF105, M~1.85E17 kg). Four systems orbit in a prograde sense, and
three in a retrograde sense. They have a different mutual inclination
distribution compared to all other TNBs, preferring low mutual-inclination
orbits. These systems have geometric r-band albedos in the range of 0.09-0.3,
consistent with radiometric albedo estimates for larger solitary
low-inclination Classical Kuiper Belt objects, and we limit the plausible
distribution of albedos in this region of the Kuiper Belt. We find that
gravitational collapse binary formation models produce a similar orbital
distribution to that currently observed, which along with a confluence of other
factors supports formation of the cold Classical Kuiper Belt in situ through
relatively rapid gravitational collapse rather than slow hierarchical
accretion. We show that these binary systems are sensitive to disruption via
collisions, and their existence suggests that the size distribution of TNOs at
small sizes remains relatively shallow.
