Centaurus A (also known as
NGC 5128 or
Caldwell 77) is a
galaxy in the
constellation of
Centaurus. It was discovered in 1826 by
Scottish astronomer
James Dunlop from his home in
Parramatta, in New South Wales, Australia. There is considerable debate in the literature regarding the galaxy's fundamental properties such as its
Hubble type (
lenticular galaxy or a giant
elliptical galaxy)=10.5px and distance (11–13 million
light-years).NGC 5128 is one of the closest
radio galaxies to
Earth, so its
active galactic nucleus has been extensively studied by professional astronomers. The galaxy is also the
fifth-brightest in the sky, making it an ideal amateur astronomy target. It is only visible from the southern hemisphere and low northern latitudes.The center of the galaxy contains a
supermassive black hole with a mass of 55 million
solar masses, which ejects a
relativistic jet that is responsible for emissions in the
X-ray and
radio wavelengths. By taking radio observations of the jet separated by a decade, astronomers have determined that the inner parts of the jet are moving at about half of the
speed of light. X-rays are produced farther out as the jet collides with surrounding gases, resulting in the creation of highly energetic particles. The X-ray jets of Centaurus A are thousands of light-years long, while the radio jets are over a million light-years long.
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