The Universe has guzzled its way through about 20 per
cent 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
The survey, to be released at the General Assembly of the
International Astronomical Union in Prague today, revealed that
about 20 per cent 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 per cent lies in dust expelled from massive stars
(and from which solid structures like the Earth and humans are
made), and about 0.01 per cent is in super-massive black
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 1000 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 Dr 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
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 stocktake.’
“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
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: Amanda Morgan, ANU Media Office
(02) 6125 5575 / 0416 249 245