The Millennium Galaxy Catalogue (MGC) is a survey of over ten thousand giant galaxies, each comprising of up to 10 billion stars as well as bulges, discs and super-massive black holes. The imaging data was obtained using the Wide Field Camera on the Isaac Newton Telescope. The survey was able to determine how much of the Universe’s matter is locked away in black holes, some of which are one million billion times more massive than the Earth. By adding up each key component it is found that the Universe has used about twenty percent of its original fuel reserves.

Tracking down what happened to normal matter dating back to the Big Bang 14 billion years ago has remained one of the most important goals for cosmologists for many years. The new survey reveals that about 20% is locked up in stars, a further 0.1% lies in dust expelled from the massive stars (and from which solid structures like the Earth and man are made), and about 0.01% is in the form of super-massive black holes. The remaining 80% are almost completely in gaseous form lying both within and between the galaxies and constitutes the reservoir from which future generations of stars may form. So the Universe will be able to form stars for a further 70 billion years approximately after which it will start to go dark.

The MGC was able to focus on the structures in which stars are arranged inside galaxies so their main components could be studied separately. The survey is the first to catalogue reliable information on the distances, sizes, colours and shapes of both the bulge and disc components of so many galaxies. On average it was found that half the stars in the Universe lie in the central bulges of galaxies, while the other half are found in discs surrounding the bulges. By measuring the concentration of stars in each galaxy’s bulge, the super-massive black hole mass at the heart of each galaxy could be also determined.

Figure 1. Sample images from the Millenium Galaxy Catalogue. [ JPEG ].

References:

• P.D. Allen, S.P. Driver, A.W. Graham, E. Cameron, J. Liske and R. De Propris, 2006, "The Millennium Galaxy Catalogue: bulge-disc decomposition of 10 095 nearby galaxies", MNRAS, 371, 2.
• J. Liske, S.P. Driver, P.D. Allen, N.J.G. Cross and R. De Propris, 2006, "The Millennium Galaxy Catalogue: a census of local compact galaxies", MNRAS, 369, 1547.
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• Cosmic stocktake reveals what's left of big bang. Press Release from The Australia National University, 18th August, 2006.
• A Matter of Darkness. Press Release from St Andrews University, 18th August, 2006.
• Presentado en la Asamblea de la Unión Astronómica Internacional el estudio “Millennium Galaxy Catalogue”. IAC Press Release, 30th August, 2006.
• K. Cooper, 2006, "Retuning the galaxy fork", Astronomy Now, 20, 15.
• S. Driver, J. Liske, 2007, "A new understanding of the visible Universe", Frontiers, 26, 11.
• Millenium Galaxy Catalogue web site.