Revealed: How our galaxies are connected

Know how galaxies across the universe are connected? Opening a new chapter in unlocking this mystery, for the first time, astronomers have taken unprecedented images of the intergalactic medium (IGM) - the diffuse gas that connects galaxies.

With Cosmic Web Imager - built at California Institute of Technology and deployed on the Hale 200-inch telescope at Palomar Observatory in California - astronomers have obtained first three-dimensional pictures of the IGM.

"The Cosmic Web Imager will make possible a new understanding of galactic and intergalactic dynamics," said Christopher Martin, a professor of physics who conceived the Imager.

It has already detected one possible spiral-galaxy-in-the-making that is three times the size of our Milky Way.

The IGM is a network of smaller and larger filaments crisscrossing one another across the vastness of space and back through time to an era when galaxies were first forming and stars were being produced at a rapid rate.

Martin describes the diffuse gas of the IGM as "dim matter", to distinguish it from the bright matter of stars and galaxies, and the dark matter and energy that compose most of the universe.

Martin and his team have now seen the first glimpse of the city of dim matter.

It is not full of skyscrapers and bridges but it is both visually and scientifically exciting, the study said.

The objects the Cosmic Web Imager has observed date to approximately 2 billion years after the Big Bang - a time of rapid star formation in galaxies.

The paper was published in the Astrophysical Journal.