Centaurus A (NGC 5128) is one of the most studied objects in the Southern sky, because it is the giant elliptical galaxy with the closest proximity to our own Milky Way. It lies 11 million light years away from the Milky Way, and is believe to have merged with another gaseous galaxy about 200 to 700 million years ago. The result of this galactic mashup: the birth of hundreds of thousands of stars in a kiloparsec-spanning ring near the core.
This is the first time that the inner structure of the galaxy has been resolved in such detail. Using the SOFI large field Infra-Red (1-2.5 micron) spectro-imager at the ESO New Technology Telescope, a research team led by Jouni Kainulainen of the University of Helsinki and Max Planck Institute for Astronomy was able to image a large ring of stars that have formed – and are still continuing to form – near the center of the galaxy. The brightest sources in the ring are red supergiants, or low-mass star clusters.
"It is important to note that it is not decisively the instrument (the telescope or the instrument attached to it) that enables us to see through dust, but the data analysis technique that is used to analyze the images taken with it. Of course, the instrument plays a big role in a sense that adequately high-quality images are needed to perform the analysis," Dr. Kainulainen said in an email interview.
"There is a fundamental difference between the images we use in our paper and the Spitzer images: the wavelength that the images cover. In the images we used in our work, the dust lane of Centaurus A shows itself as "a shadow", or more precisely, as an absorption feature (the wavelength is 1-2 micrometers). The Spitzer images represent somewhat longer wavelengths, and show the radiation emitted by the dust itself. As a concrete example, the most famous Spitzer image of Centaurus A … shows a parallelogram-like structure, but the image describes radiation mainly from dust, not from stars," he said.
