Tidal Tails of Galactic Open Clusters: A Review of Methods, Evidence, and Sources of Disagreement

Tidal tails of open clusters provide direct observational evidence of cluster mass loss and dynamical interaction with the Galactic tidal field. The advent of Gaia astrometry has enabled systematic detection of extended stellar structures around nearby clusters, revealing that many systems exhibit complex and extended morphologies beyond their classical tidal radii. In this review, we summarise the current observational and theoretical status of tidal tails in open clusters, focusing on results obtained in the Gaia era. We compare different detection methodologies, including density-based clustering, probabilistic models, and orbit-based selection techniques, and discuss how methodological choices influence the inferred morphology of tidal structures. While the Hyades remains the most robust example of well-defined tidal tails, other clusters show a wide range of extended features with varying degrees of coherence and symmetry. We argue that the diversity of reported results reflects both genuine astrophysical variation and systematic differences in analysis approaches. We outline prospects enabled by upcoming astrometric, spectroscopic, and photometric surveys, which will allow a more unified and physically consistent understanding of cluster dissolution in the Milky Way.