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Paris (AFP)
Looking at the early Universe some 12 billion years ago, scientists in France first saw the glowing filaments of hydrogen gas known as the “cosmic web,” they said Thursday.
Cosmological models have long predicted its existence, but until now the cosmic web had never been directly observed and captured in images.
Eight months of observation with the European Southern Observatory’s Very Large Telescope and a year of data crunching revealed the filaments as they existed just one to two billion years after the Big Bang.
But the biggest surprise, scientists said, were simulations showing that the light came from billions of previously invisible – and unexpected – dwarf galaxies that spawned billions of stars.
The findings were reported in the journal Astronomy & Astrophysics.
“After an initial period of darkness, the Universe burst with light and produced an enormous number of stars,” senior author Roland Bacon, a scientist at the Center for Astrophysical Research in Lyon, told AFP.
“One of the big questions is what ended that period of darkness,” which led to a phase in the early Universe known as re-ionization, he said.
Until now, astronomers had only caught partial and indirect glimpses of the cosmic web through quasars, the powerful rays of which, like car headlights, reveal clouds of gas along the line of sight.
But these regions do not represent the entire network of filaments where most of the galaxies – including ours – were born.
– Sanitary new depths –
“These findings are fundamental,” said Emanuele Daddi, a researcher with the Atomic Energy Commission who did not participate in the study.
“We have never seen gas emissions on this scale, which is essential for understanding how galaxies form.”
The team trained ESO’s Very Large Telescope – equipped with a 3D spectrograph called MUSE – on a single part of the sky for more than 140 hours.
Together, the two instruments form one of the most powerful observation systems in the world.
The selected area is part of the Hubble Ultra-Deep Field, which contains the deepest image of the cosmos ever obtained.
But the new images probe new depths of the early Universe – 40 percent of newly discovered galaxies were beyond Hubble’s reach.
While these galaxies – 10 to 12 billion light-years away – are too faint to be detected separately with current instruments, their existence is likely to enhance and challenge existing models of galaxy formation.
Scientists are only now beginning to investigate their implications, the researchers said.
Astronomers from the Lagrange Laboratory for the University of Cote d’Azur contributed to the research.
© 2021 AFP