active galactic nucleus

American

[ak-tiv-guh-lak-tik noo-klee-uhs, nyoo-klee-uhs] / ˈæk tɪv gəˈlæk tɪk ˈnu kli əs, ˈnju kli əs /

noun

Astronomy. a large, extremely bright region at the center of a galaxy, its brightness thought to come from the huge amounts of radiant energy emitted by dust particles and gases falling into a massive black hole within the region.

active galactic nucleus Scientific

/ ăk′tĭv /

See under galactic nucleus

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active galactic nucleus

Astronomers call this an active galactic nucleus, or AGN.

From Science Daily ● Jul. 18, 2026

The steep rise in the spectrum that inspired the name The Cliff can be explained by a dense, spherical, turbulent gas envelope around an active galactic nucleus.

From Science Daily ● Nov. 29, 2025

A quasar is an active galactic nucleus that is believed to be energized by a supermassive black hole.

From Salon ● Jul. 4, 2023

The second theory is that they result from the activities of an active galactic nucleus, with radio jets spewing particles to create the ORC’s shape.

From Scientific American ● Mar. 29, 2022

How does the presence of an active galactic nucleus in a starburst galaxy affect the starburst process?

From Textbooks ● Oct. 13, 2016

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Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023