Distant galaxy cluster sheds light on 'cosmic skeleton'
Astronomers have discovered a gigantic assembly of galaxies located almost seven billion light-years from Earth.
"In our cosmic vicinity, stars form in galaxies and galaxies usually form groups and clusters of galaxies," says Masayuki Tanaka from ESO, who led the new study. "The most widely accepted cosmological theories predict that matter also clumps on a larger scale in the so-called 'cosmic web', in which galaxies, embedded in filaments stretching between voids, create a gigantic wispy structure."
These filaments are millions of light years long. Tanaka describes them as the 'skeleton of the Universe' - galaxies gravitate towrds them, and immense galaxy clusters form at their intersections. Scientists don't fully understand how they are created, and this is the first solid evidence of their existence at great distances.
The team led by Tanaka discovered a large structure around a distant cluster of galaxies in images they obtained earlier. They have now used two major ground-based telescopes - ESO's Very Large Telescope and the Subaru Telescope in Japan - to study it in greater detail.
The team has now identified several groups of galaxies surrounding the main galaxy cluster. They could distinguish tens of such clumps, each typically ten times as massive as our own Milky Way galaxy — and some a thousand times more massive — and they reckon the mass of the cluster amounts to at least ten thousand times the mass of the Milky Way.
The filament is located about 6.7 billion light-years away, and extends over at least 60 million light-years. The newly uncovered structure probably extends beyond the field probed by the team, and there are plans to map it thoroughly.
The research appears in the Astronomy & Astrophysics Journal.