Stephan's Quintet is a visual grouping of five galaxies in the constellation Pegasus, discovered in 1877 by Édouard Stephan, and is the first compact galaxy group ever found. While called a "quintet," only four galaxies (NGC 7317, 7318A, 7318B, 7319) are gravitationally bound and interacting, while the fifth (NGC 7320) is a closer foreground galaxy. The interacting galaxies are in a "cosmic dance," with gravitational forces creating shockwaves, tidal tails, and intense star formation, making it a key target for studying galaxy evolution.
Key characteristics
Discovery: First compact galaxy group discovered, found by Édouard Stephan in 1877.
Location: Constellation Pegasus, about 290 million light-years away (the four interacting galaxies).
Members: Four interacting galaxies (NGC 7317, 7318A, 7318B, 7319) and one foreground galaxy (NGC 7320).
Interactions: The galaxies are colliding, with NGC 7318B crashing through the group at nearly 2 million mph, creating shockwaves that heat gas and trigger star formation.
Features: Shows tidal tails of gas and stars, bright clusters of young stars, and glowing hydrogen clouds.
Significance: A prime example for studying galaxy mergers, evolution, and the effects of galactic collisions.
Recent observations
The James Webb Space Telescope (JWST) has provided unprecedented detail, revealing star formation and gas disturbances.
Newer observations using instruments like WEAVE have clocked the collision speed and studied the shockwave's dual nature (fast through cold gas, weaker through hot gas). Image Credit NASA, ESA, and the Hubble SM4 ERO Team
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