Dany Page, Madappa Prakash, James M. Lattimer, and Andrew W. Steiner: Rapid Cooling of the Neutron Star in Cassiopeia A Triggered by Neutron Superfluidity in Dense Matter, Phys. Rev. Lett. 106,8 (2011) 081101 http://arxiv.org/abs/1011.6142 provides, allegedly, the first direct evidence of this. The critical temperature for superfluidity in this star's neutron-matter is estimated to be 5*10^8 Kelvin.