Interacting galaxy

An interacting galaxy is gravitationally influencing or being influenced by another galaxy. The interaction can distort galactic structure, draw out tidal features, and trigger bursts of star formation.

Galaxy merger: A collision and eventual coalescence of two or more galaxies under gravity. A close interaction can end in merger, transforming both galaxies into a single remnant.
Antennae Galaxies: A pair of colliding galaxies in the constellation Corvus, marked by long tidal tails and active star formation. Their overlapping bodies and tails make a nearby example of a major galactic collision.
Galaxy morphology: The classification and description of galaxies by their observable shapes and structures. Tidal distortions can change the forms used to classify galaxies.
Isolated galaxy: A galaxy with no nearby companion exerting a substantial gravitational influence. It provides a comparison for separating interaction-driven features from ordinary galactic structure.
Dynamical friction: The deceleration of a massive object moving through surrounding matter because its gravity creates a trailing wake. The wakes raised in dark matter and stars can drain orbital energy and bring galaxies together.
Mice Galaxies: The interacting galaxy pair NGC 4676, named for its long, curved tidal tails. Their tails preserve evidence of a close encounter between two disk galaxies.
Star formation: The process by which dense regions of gas collapse to form stars. Interactions can compress or funnel gas, changing the rate and location of star formation.
Ram-pressure stripping: The removal of a galaxy's gas by pressure from its motion through a surrounding medium. It can strip gas without requiring a close gravitational encounter between galaxies.
Tidal force: A spatial variation in gravitational force across an extended object. Differential gravity stretches interacting galaxies and pulls out their tails.
Whirlpool Galaxy: The spiral galaxy M51, accompanied by the smaller interacting galaxy NGC 5195. Its companion's passage is linked to disturbances in the spiral structure.

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Grand-design spiral galaxyRelated: A companion's gravity can drive conspicuous spiral arms in some grand-design systems.