A huge power house rages at the heart of the active galaxy Centaurus A, 12 million light years away. The power house is the central supermassive black hole, estimated at hundreds of millions of times the mass of the Sun. Gas, dust, and other interstellar material spiral into the gravity well at a ferocious rate. All this activity produces vast amounts of energy that emits over large swaths of the electromagnetic spectrum producing what is known as an active galaxy. Centaurus A is such an active galaxy and produces radio energy, gamma rays, and x-rays. Active galaxies like this one are the most luminous sources of electromagnetic radiation in space.
Galactic central black holes produce narrow jets of particles that travel at near the speed of light, shooting out from above and below the plane of the accretion disk. But the Nasa Fermi Gamma Ray Telescope has now uncovered vast gas plumes that literally dwarf the 60,000 light year wide Centaurus A galaxy. The plumes are these narrow jets that have puffed outwards over millions of years, each plume is over a million light years long. You could fit 10 Milky Way Galaxies along one of the plume’s length. The sheer intensity and unimaginable strength of the black hole is evident in new images released by Nasa.
The image above shows the gamma ray radiation from the gas plumes, the gamma ray output has been found to have 100 billion times the energy of radio waves. Centaurus A has been known as a radio galaxy, but the gamma ray output is far stronger. If we would have had gamma ray telescopes first before radio telescopes, Centaurus A would be a gamma ray galaxy.
The image below shows the unimaginable scale of the radio emitting gas plumes that extend 1.4 million light years from above and below the galaxy. Active galaxies are known to emit x-rays, but the observation by the Fermi Telescope of Centaurus A is the first to see these relativistic jets coming from central black holes actually producing gamma rays.
Centaurus A is the closest and brightest active galaxy to Earth, and is characterised by the thick dark band of dust that crosses the centre. It is thought to have formed from the collision of two normal galaxies ending up in a maelstrom of dust lanes, gas clouds, and star formation.
The gamma ray emitting gas plumes, and especially the radio plumes almost make the visible part of Centaurus A insignificant. The power of supermassive black holes defy belief, and as in a lot of astronomy, what is actually discovered is nothing like we would expect. Astronomy continues to astound and surprise with even bigger, faster, brighter, more powerful, and more incredible facts and images as ever before.
John Brady, 2nd April 2010