At the centre of a nearby galaxy lurks an object of huge interest, a super-massive black hole. CSIRO scientists have used their radio telescopes to take a picture of the galaxy surrounding it, a task some thought could not be done, because of the sheer size and radio brightness of the scene. The image of Centaurus A took about 1,200 hours of observations and a further 10,000 hours of computer processing to put together, but the work is already beginning to bear fruit.
“We didn’t generate this image just to make a pretty picture,” says lead scientist Ilana Feain of CSIRO Astronomy and Space Science. “We want to understand in detail how the energy from super-massive black holes influences the formation and evolution of their host galaxies.”
At a mere 12 million or so light-years away, Centaurus A is by far the closest galaxy to our own to contain an active super-massive black hole; it is about 50 million times the mass of the Sun. The galaxy was first recorded at Parramatta, Australia’s first major observatory, and its long history and close proximity have made it a popular subject of study—so much so that it has become something of a model system for studying galaxies. In 2009 an international conference in Sydney was devoted solely to Centaurus A—during which the new image was unveiled.
“The image shows powerful radio emissions billowing out from just around the black hole. These radio jets extend millions of light years away from the black hole itself, beyond the visible galaxy into the comparatively empty intergalactic medium,” says Ilana.
The picture of Centaurus A was constructed from a mosaic of observations taken by CSIRO’s Australia Telescope Compact Array and the Parkes radio telescope.
“This image shows how the jets interact with the interstellar and intergalactic medium. When we combine this information with observations from other telescopes that operate across the electromagnetic spectrum from the infrared through the optical to high energy gamma rays, we can start to piece together the physics of the history of these galaxies.”