Universe Has Used Up a Fifth of Its Gas Tank|
MIL/UT, Aug 19, 2006.
the Big Bang, 13.7 billion years ago, the Universe has converted 20% of
its original matter into stars. This is according to a new survey by an
international team of astronomers.
Other than stars, a tiny fraction of non-primordial material is dust
expelled from massive stars and supermassive black holes. The survey
was made using the Millennium Galaxy Catalogue, which contains more
than 10,000 large galaxies. It looks like the Universe will need
another 70 billion years to use up all its original fuel.
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 University.
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 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 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 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
“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.