Cygnus A

Astron.

a strong radio source in the constellation Cygnus associated with a distant peculiar galaxy.

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Radio-emitting galaxy lying in the constellation Cygnus, about 700 million light-years from Earth.

It is the brightest cosmic source of radio waves in the sky and the first radio galaxy to be detected. Because of its peculiar divided appearance, it was once thought to be two galaxies colliding. Astronomers now believe it to be a single galaxy with a large black hole at its core; emanating from this central region are two opposing jets of hot gas that end in radio-and X-ray-emitting lobes called "hot spots." See also active galactic nucleus.

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▪ astronomy

      most powerful cosmic source of radio waves known, lying in the northern constellation Cygnus about 500,000,000 light-years (4.8 × 10²¹ km) from Earth. It has the appearance of a double galaxy. For a time it was thought to be two galaxies in collision, but the energy output is too large to be accounted for in that way. Radio energy is emitted from Cygnus A at an estimated 10⁴⁵ ergs per second, more than 10¹¹ times the rate at which energy of all kinds is emitted by the Sun. The source of the energy of Cygnus A remains undetermined.

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