A 22° tidal tail for Palomar 5

Using Data Release 4 of the Sloan Digital Sky Survey, we have applied an optimal-contrast, matched-filter technique to trace the trailing tidal tail of the globular cluster Palomar 5 to a distance of 18 degrees 5 from the center of the cluster. This more than doubles the total known length of the tail to some 22 degrees on the sky. Based on a simple model of the Galaxy, we find that the stream's orientation on the sky is consistent at the 1.7 sigma level with existing proper-motion measurements. We find that a spherical Galactic halo is adequate to model the stream over its currently known length, and we are able to place new constraints on the current space motion of the cluster.