evidence for the superfluidity of neutron star interiors. Perhaps, the most striking manifestations of their superfluidity are the long (on time-scales from several hours to hundreds of days) relaxations that follow the glitches in the spin and spin-down rates of some pulsars. Although the majority of pulsars are very precise clocks, timing observations reveal persistent random fluctuations in times of arrival of radio signals. Some pulsars show long-term periodicities in their spin-characteristics and periodic changes of their pulse shape. However, the relation between the superfluidity of neutron star interiors and these anomalies of pulsar timing is not firmly established yet.

Further evidence for the superfluidity of neutron star interiors came in the 1980s with the advent of the orbiting x-ray satellites. The measurements of the thermal radiation from a dozen or so hot neutron stars provided indirect information on the temperature of superfluid phases in neutron stars. Theoretical thermal histories of superfluid neutron stars are consistent with the x-ray data (within the limits of our knowledge of the input physics). Non-superfluid stars, as a rule, cool too fast to below the threshold of detection.

Apart from the radiation in the electro-magnetic spectrum, neutron stars are expected to be primary sources 