Australian astronomers say they've found proof of a vast filament of material that connects our Milky Way galaxy to nearby clusters of galaxies and on to the rest of the universe.
The Australian National University team examined the positions of ancient groupings of stars called globular clusters, and found that they form a narrow plane around the Milky Way rather than being scattered across the sky.
And the Milky Way’s own entourage of small satellites also inhabits the same plane.
"What we have discovered is evidence for the cosmic thread that connects us to the vast expanse of the universe," says Dr Stefan Keller of the Research School of Astronomy and Astrophysics at ANU.
"The filament of star clusters and small galaxies around the Milky Way is like the umbilical cord that fed our galaxy during its youth."
Because of the Big Bang and the dominance of dark matter in the universe, he says, ordinary matter is driven, like foam on the crest of a wave, into vast interconnected sheets and filaments stretched over enormous cosmic voids – "much like the structure of a kitchen sponge."
"Unlike a sponge, however, gravity draws the material over these interconnecting filaments towards the largest lumps of matter, and our findings show that the globular clusters and satellite galaxies of the Milky Way trace this cosmic filament," he says.
Most globular clusters are the central cores of small galaxies that have been drawn along the filament by gravity. Once these small galaxies got too close to the Milky Way, the majority of stars were stripped away and added to our galaxy, leaving only their cores.
"It is thought that the Milky Way has grown to its current size by the consumption of hundreds of such smaller galaxies over cosmic time," says Keller.