  Baryon and quark superfluidity in the cooling of neutron stars are
investigated. Observations could constrain combinations of the neutron or
Lambda-hyperon pairing gaps and the star's mass. However, in a hybrid star with
a mixed phase of hadrons and quarks, quark gaps larger than a few tenths of an
MeV render quark matter virtually invisible for cooling. If the quark gap is
smaller, quark superfluidity could be important, but its effects will be nearly
impossible to distinguish from those of other baryonic constituents.
