Centaurus A (also known as NGC 5128 or Caldwell 77) is a prominent galaxy in the constellation of Centaurus. It was discovered in 1826 by Scottish astronomer James Dunlop at the Sydney Observatory. NGC 5128 is one of the closest radio galaxies to Earth (10-16 million light years). The galaxy is also the fifth brightest in the sky, making it an ideal amateur astronomy target.

The center of the galaxy contains a supermassive black hole with a weight equivalent to 55 million solar masses, which ejects a relativistic jet that is responsible for emissions in the X-ray and radio wavelengths. X-rays are produced farther out as the jet collides with surrounding gases resulting in the creation of highly energetic particles. The radio jets of Centaurus A are over a million light years long.