Antennae Galaxies

The Antennae Galaxies are the interacting pair NGC 4038 and NGC 4039, whose collision has drawn long tidal tails of stars and gas.

Tidal interaction: A gravitational encounter that deforms orbiting bodies and redistributes their material. The galaxies’ long tails are direct products of gravitational forces during their encounter.
NGC 4038: A barred spiral galaxy that forms one half of the Antennae system. Its stars and gas contribute to the system’s disturbed structure and tidal tails.
Galaxy merger: The gravitational combination of two or more galaxies into a single system. The Antennae are a nearby example of a merger in progress.
Tidal dwarf galaxy: A small galaxy formed from gas and stars pulled out during a galactic interaction. Material in the Antennae’s tails may gather into self-gravitating dwarf systems.
Tidal tail: An elongated stream of stars and gas pulled from a galaxy by gravitational interaction. The Antennae’s two prominent tails give the pair its name.
NGC 4039: A spiral galaxy that forms one half of the Antennae system. Its interaction with NGC 4038 shapes the pair’s distinctive overlapping appearance.
Galaxy interaction: A gravitational encounter between galaxies that can alter their shapes and evolution. Their distorted forms arise from mutual gravitational interaction.
Globular cluster: A dense, roughly spherical collection of old stars bound by gravity. Some young clusters born in the encounter may resemble globular clusters as they age.
Dynamical friction: The loss of orbital energy by a massive body moving through a background of matter. It helps the two galaxies lose orbital energy and approach coalescence.
NGC 4038/39 star clusters: Young, compact groups of stars observed throughout the Antennae Galaxies. Their abundance provides evidence that the collision has stimulated star formation.

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