Detection of a 50 degree-long Trailing Tidal Tail for the Globular
  Cluster M5
  Using photometry and proper motions from Gaia Data Release 2, we detect a 50
degree-long stream of about 70 stars extending westward from the halo globular
cluster M5. Based on the similarities in distance, proper motions, inferred
color-magnitude distribution, and trajectory, we identify this stream as the
trailing tidal tail of M5. While the surface density of stars is very low (~1.5
stars per square degree, or approximately 35 magnitudes per square arcsecond),
selecting only stars having proper motions consistent with the orbit of the
cluster yield a detection significance ~10 sigma. While we find a possible
continuation of the stream to ~85 degrees, increasing foreground contamination
combined with a greater predicted stream distance make it difficult to detect
with current data even if the stream continues unabated. The non-uniform
distribution of stars in the stream appears to be consistent with episodic
tidal stripping, with the most recently shed stars now trailing the cluster by
tens of degrees. We provide a table of the highest-ranked candidate stream
stars for ongoing and future spectroscopic surveys.
