Huge galaxy string challenges space theory (Forwarded)

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Dr Paul Francis
Tel: 0402 640 364

Thursday, 8 January 2004

HUGE GALAXY STRING CHALLENGES SPACE THEORY

An enormous string of galaxies 300 million light-years long has
been discovered in the remote Universe, challenging existing
theories about how the Universe evolved.

The remote area was formed very early, at a time when the Universe was a
fifth of its present age and the presence of the galaxy string defies
existing models, which can not explain how a string this big could have
formed so long ago.

This is the first time astronomers have been able to map an area in the
early Universe big enough to reveal such a galaxy structure.

ANU astronomer Dr Paul Francis, who coordinated the international
research team, said the galaxy string lay 10,800 million light-years
away. Light travels almost 9.5 trillion kilometres in one light-year, so
our observation of the string is as it appeared 10.8 billion years ago.
The universe was formed during the Big Bang approximately 13.7 billion
years ago.

"We have detected 37 galaxies and one quasar in the string, but it
probably contains many thousands of galaxies," Dr Francis said.

"The really exciting aspect of this finding is that it sheds new light on
the formation of the universe. We are looking back four-fifths of the way
to the beginning of the Universe and the existence of this galaxy string
will send astrophysicists around the world back to the drawing board, to
re-examine theories of the formation of the Universe."

The string was discovered by Dr Francis, Dr Povilas Palunas of the
University of Texas, Dr Harry Teplitz of the California Institute of
Technology, Dr Gerard Williger of Johns Hopkins University and Dr Bruce
E. Woodgate of NASA Goddard Space Flight Center, using telescopes in
Chile and at Siding Spring Observatory in New South Wales.

The team were refused time on a US telescope because many American
astronomers believed the observations were technically impossible. The
findings have been presented at the American Astronomical Society meeting
in Atlanta.

The team compared their observations to supercomputer simulations of the
early Universe, which could not reproduce strings this large. "The
simulations tell us that you cannot take the matter in the early Universe
and line it up in strings this large," Dr Francis said.

"There simply hasn't been enough time since the Big Bang for it to form
structures this colossal.

"All we are seeing is the brightest few galaxies. That's probably far
less than 1 per cent of what's really out there, most of which is
mysterious invisible dark matter. It could be that the dark matter is not
arranged in the same way as the galaxies we are seeing."

Recently, evidence has accumulated for the presence of dark matter in the
Universe, an invisible form of matter only detectable by the
gravitational pull it exerts on ordinary matter (and light). There are
many possibilities for what dark matter might be, but its true nature is
currently unknown.

In recent years, it had been found that in the local Universe, dark
matter is distributed on large scales in very much the same way as
galaxies are, rather than being more clumpy, or less. But go back 10
billion years and it could be a very different story. Galaxies probably
form in the centre of dark matter clouds. But in the early Universe, most
galaxies had not yet formed, and most dark matter clouds will not yet
contain a galaxy.

"To explain our results the dark matter clouds that lie in strings must
have formed galaxies, while the dark matter clouds elsewhere have not
done so. We've no idea why this happened -- it's not what the models
predict," Dr Francis said.

The astronomers say the next step is to map an area of sky ten times
larger, to get a better idea of the large-scale structure. Several such
surveys are currently under way. The research was funded by NASA and the
Australian National University.

Further details and a movie animation of the galaxy string is available
on the Internet at:
http://www.mso.anu.edu.au/~pfrancis/www/string/