Centaurus A

Centaurus A, or NGC 5128, is a nearby galaxy with a bright active nucleus that makes it one of the sky’s strongest radio sources.

Supermassive black hole: A black hole with a mass millions to billions of times that of the Sun. A supermassive black hole is thought to power Centaurus A’s active nucleus.
NGC 5128: The New General Catalogue designation for the galaxy commonly called Centaurus A. This catalogue name appears in optical studies, while Centaurus A is more familiar in radio astronomy.
Galaxy merger: An interaction in which two or more galaxies collide and combine through gravity. A merger between a large elliptical galaxy and a smaller gas-rich galaxy is a leading explanation for Centaurus A’s structure.
Very-high-energy gamma-ray astronomy: The study of gamma rays with energies above roughly 100 gigaelectronvolts using ground-based detectors. Centaurus A is observed at high energies to investigate particle acceleration around its active nucleus.
Messier 87: A giant elliptical galaxy in the Virgo Cluster with a supermassive black hole and prominent relativistic jet. Its jet and black hole provide a better-known comparison for Centaurus A’s active nucleus.
Relativistic jet: A narrow outflow of matter moving at speeds close to the speed of light. Centaurus A’s central engine launches jets that feed its radio-emitting lobes.
Centaurus A radio lobes: The large regions of radio-emitting plasma extending on either side of Centaurus A’s nucleus. They make the galaxy’s radio structure vastly larger than its visible stellar body.
Elliptical galaxy: A galaxy with a smooth, rounded appearance and little organized star formation compared with spiral galaxies. Centaurus A’s main stellar body is elliptical, despite its conspicuous dust lane.
Ultra-high-energy cosmic ray: A cosmic ray particle with an energy far exceeding that attainable in terrestrial accelerators. Centaurus A has been considered a possible source because of its proximity and powerful jets.
Cygnus A: A powerful radio galaxy whose two bright lobes make it one of the strongest extragalactic radio sources. Compared with Cygnus A, Centaurus A is much nearer and less powerful, enabling detailed study.

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