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/