A matter of darkness

Thursday 17 August 2006

A new study into where the normal matter produced by the Big Bang is today, has discovered that twenty percent has already turned into stars.

The research, led by the University of St Andrews, involved 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 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 they found that the Universe has ‘guzzled’ its way through about twenty percent of its original fuel reserves.

Project leader Dr Simon Driver of the University of St Andrews said: “The simplest prognosis is that the Universe will be able to form stars for a further 70 billion years or so after which it will start to go dark. However, unlike our stewardship of the Earth, the Universe is definitely tightening its belt with the rate at which new stars are forming steadily decreasing.”

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,” Dr Driver continued.

The survey involved scientists from Australia, Germany and the UK, and resulted in the Millennium Galaxy Catalogue (MGC), constructed from over 100 nights of telescope time in the Canary Islands, Australia and Chile.

“What is new about the MGC is that it focuses on the structures in which stars are arranged inside galaxies. We have literally dismantled each galaxy so that we can study the main components separately,¿ said Dr Driver.

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. Dr Driver and his team found that on average 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, we have also been able to determine the super-massive black hole mass at the heart of each galaxy¿, said Dr Alister Graham of the Australian National University.

“It was then a simple matter of summing these up to determine how much of the Universe’s matter is locked away in such monstrous black holes.”

The survey was presented at the General Assembly of the International Astronomical Union in Prague this week. Financial support for this project was jointly provided by the UK Particle Physics and Astrophysics Research Council and the Australian Research Council.



UNITED KINGDOM: Dr Simon Driver, Director of St Andrews’ Observatory, University of St Andrews, St Andrews, Fife, SCOTLAND Mobile: 0791930 5906 (Friday) +44-(0)1334-461680 (after Friday) E-mail: [email protected]

GERMANY: Dr Jochen Liske, European Southern Observatory, Garching, GERMANY +49-(0)89-32006582 E-mail: [email protected]

AUSTRALIA: Drs Alister Graham and Paul Allen, The Australian National University, Canberra, AUSTRALIA +61-(0)2-6125-6713 E-mail: [email protected] & [email protected]

MGC website: http://www.eso.org/~jliske/mgc

Issued by Beattie Media – www.beattiegroup.com on behalf of the University of St Andrews

Contact Gayle Cook, Press Officer on 01334 467227 / 462529, mobile 07900 050 103, or email gec3@st- andrews.ac.uk

Ref: Matter of darkness 180806.doc

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