Jane O'Dwyer jane.odwyer at anu.edu.au
Fri Aug 18 00:45:45 CEST 2006

News from The Australian National University

The Universe has guzzled its way through about 20% of its normal matter,
or original fuel reserves, according to findings from a survey of the
nearby Universe by an international team of astronomers involving
researchers at the Australian National University. 

The survey, to be released at the General Assembly of the International
Astronomical Union in Prague today, revealed that about 20% of the
normal matter or fuel that was produced by the Big Bang 14 billion years
ago is now in stars, a further 0.1% lies in dust expelled from massive
stars (and from which solid structures like the Earth and humans are
made), and about 0.01% is in super-massive black holes.

The survey data, which forms a 21st century database called the
Millennium Galaxy Catalogue, was gathered from over 100 nights of
telescope time in Australia, the Canary Islands and Chile, and contains
over ten thousand giant galaxies, each of these containing 10 million to
10 billion stars.

According to the survey leader Dr Simon Driver of St Andrews University,
Scotland, the remaining material is almost completely in gaseous form
lying both within and between the galaxies, forming a reservoir from
which future generations of stars may develop.

"I guess 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," said Driver. "However, unlike our stewardship of the
Earth the Universe is definitely tightening its belt with a steady
decline in the rate at which new stars are forming."

Dr Alister Graham, an astronomer at The Australian National University
who worked on the survey, said that the team of researchers were able
determine how much of matter is in the stars through a 'cosmic

"We needed to measure the stellar mass within a representative volume of
the local Universe. This required accurate and complete distance
information for all the galaxies of stars that we imaged.  This is where
the Australian telescopes played a key role," Dr Graham said.

One of the unique aspects of this program was the careful separation of
a galaxy's stars into its central bulge component and surrounding
disc-like structure. This allowed the researchers to determine that, on
average, roughly half of the stars in galaxies reside in discs and the
other half in bulges.

"Measuring the concentration of stars in each galaxy's bulge is what
enabled us to determine their central super-massive black hole masses,"
said Dr Graham.  "Some of these are up to one million billion times more
massive than the Earth.  Once we had these masses it was a simple task
of summing them up to determine how much of the Universe's matter is
locked away in black holes at the centres of galaxies."

Dr Graham said next-generation telescopes such as the Giant Magellan
Telescope, currently in production, will enable astronomers to directly
measure black hole masses in galaxies ten times further away and thus
ten times further back in time. "In effect, we'll soon be able to
observe how galaxies and their black holes evolved into what we see
around us today."

Other members of the research team include Paul Allen and Ewan Cameron
of the Australian National University, Jochen Liske of the European
Southern Observatory, and Roberto De Propris of the Cerro Tololo
Inter-American Observatory.

The Millennium Galaxy Catalogue consists of data from the
Anglo-Australian Telescope, The Australian National University's 2.3 m
telescope at Siding Spring Observatory, the Isaac Newton Telescope and
the Telescopio Nazionale Galileo at the Spanish Observatorio del Roque
de Los Muchachos of the Instituto de Astrofisica de Canarias, and also
from the Gemini and ESO New Technology Telescopes in Chile.

Financial support for this project was jointly provided through grants
from the Australian Research Council and the United Kingdom's Particle
Physics and Astrophysics Research Council.

A schematic diagram and an image showing sample survey galaxies are
available to accompany this story.

For Further information:

Dr Alister Graham, (02) 6125 6173 or graham at mso.anu.edu.au

Amanda Morgan, ANU Media Office (02) 60125 5575/0416 249 245
Simon Couper, ANU Media Office (02) 6125 54171/ 0416 249 241

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