An apparent structure of stars or gas linking one galaxy with another. In some cases this may be the result of physical (tidal) interaction between the two galaxies, as in the case of the Antennae. In other cases the feature may be an observational artefact, or a chance, line-of-sight superposition of luminous material in the galaxies that is unrelated to any interaction. A combination of both artefact and line-of-sight effects probably accounts for the apparent bridge between the quasar Markarian 205 and the spiral galaxy NGC 4319, which have very different velocities of recession (21 000 and 1700 km/s respectively). A chain of galaxies linking two clusters or groups of galaxies is also sometimes known as a bridge.
Subjects: Astronomy and Astrophysics.