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We examine the spatial clustering of blue horizontal branch (BHB) stars fromthe $\textit{u}$-band of the Canada-France Imaging Survey (CFIS, a component ofthe Ultraviolet Near-Infrared Optical Northern Survey, or UNIONS). All majorgroupings of stars are associated with previously known satellites, and amongthese is NGC 5466, a distant (16 kpc) globular cluster. NGC 5466 reportedlypossesses a long stellar stream, although no individual members of the streamhave previously been identified. Using both BHBs and more numerous red giantbranch stars cross-matched to $\textit{Gaia}$ Data Release 2, we identifyextended tidal tails from NGC 5466 that are both spatially and kinematicallycoherent. Interestingly, we find that this stream does not follow the same pathas the previous detection at large distances from the cluster. We trace thestream across 31$^{\circ}$ of sky and show that it exhibits a very strongdistance gradient ranging from 10 $<$ R$_{helio}$ $<$ 30 kpc. We compare ourobservations to simple dynamical models of the stream and find that they areable to broadly reproduce the overall path and kinematics. The fact that NGC5466 is so distant, traces a wide range of Galactic distances, has anidentified progenitor, and appears to have recently had an interaction with theGalaxy's disk, makes it a unique test-case for dynamical modelling of the MilkyWay.

Uncovering fossils of the distant Milky Way with UNIONS: NGC 5466 and its stellar stream