Hubble's unique view
of Centaurus A
by Amanda Doyle
for ASTRONOMY NOW
Posted: 16 June 2011
The Hubble Space Telescope has captured a dramatic view of the peculiar galaxy Centaurus A. This close-up of the centre of the galaxy, taken with the Wide Field Camera 3, shows unprecedented detail of the wispy dust lanes and glowing star forming regions.
The Hubble Space Telescope has observed the centre of the galaxy Centaurus A in fascinating detail. Image: NASA, ESA.
The new shot of Centaurus A, which also goes by the name NGC 5128, is a multi-wavelength image comprising the ultraviolet, visible and near-infrared regions. The ultraviolet light is most likely emitted from young stars and the observations in the near-infrared give a fascinating glimpse beyond some of the otherwise impenetrable dust clouds. These dust clouds are part of what make Centaurus A so unusual. At first glance in the visible region, it appears to be an elliptical galaxy. However elliptical galaxies are not expected to have the vast regions of dust that are evident here. The murky dust lanes, which absorb visible light, are usually associated with spiral galaxies.
The most likely explanation is that a giant elliptical galaxy collided with and swallowed a smaller spiral galaxy. Not only would this explain the presence of dust, but it would also explain the star forming regions, shown in red in this picture. Elliptical galaxies mostly contain older, redder stars and yet Centaurus A is awash with bright new stars and star forming regions.
When Centaurus A is seen in a wider field of view, it is obviously warped. This is another piece of evidence that points to a violent collision between two galaxies. The Spitzer Space Telescope, observing in the mid-infrared, has also recently detected what appears to be the remains of a barred spiral galaxy in the centre of Centaurus A.
A wider-field view of the warped shape of Centaurus A along with the jets emanating from it. Image: X-ray: NASA/CXC/CfA/.; Submillimeter: MPIfR/ESO/APEX/A..; Optical: ESO/WFI.
Another famous feature of Centaurus A are the spectacular radio and X-ray jets (not visible in the Hubble Space Telescope image), which show that this is an active galaxy. The jets are most likely caused by the massive black hole in the centre of the galaxy, but exactly how they are formed still remains a mystery.
Centaurus A is eleven million light years from Earth, and is the fifth brightest galaxy in the sky as well as the closest active galaxy to us. It is bright enough to easily be seen through binoculars by those that live in the southern hemisphere or lower latitudes of the northern hemisphere. Larger telescopes will be able to pick out some of the detail in the dust lanes.
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