Although the gas filaments in which galaxies are born have long been predicted by cosmological models, to date we have had no real images of these materials. Now, for the first time, several filaments of the ‘cosmic web’ have been observed directly using the MUSE instrument (1) installed on the ESO Very Large Telescope in Chile. These observations of the first Universe, 1 to 2 billion years after the Great Bang, indicate that there are many unexpectedly disturbed galaxies to date. Produced by an international collaboration led by the Center de Recherche Astrophysique de Lyon (CNRS / Université Lyon 1 / ENS de Lyon), also includes the Lagrange laboratory (CNRS / Université Côte d ‘Azur / Observatoire de la Côte d’Azur) (2), the study is published on 18 March 2021 in the journal Astronomy & Astronomy.
The filamentary structure of hydrogen gas in which galaxies form, known as the cosmic web, is one of the main predictions of the Big Bang model and galaxy formation. Until now, all that was known about the net was limited to a few specific areas, especially in the case of quasars, which have powerful radiation acting as car lights, reflecting gas clouds on the line of sight. However, these segments represent poorly of the entire network of filaments where most galaxies were born, ourselves included. It was a sacred sight to look directly at the faint light emitted by the gas that makes up the filaments, which has now been reached by an international team with Roland Bacon, CNRS researcher at the Center de Recherche Astrophysique de Lyon (CNRS / Université Lyon 1 / ENS de Lyon).
The team took a bold step by unveiling the ESO Very Large Telescope, equipped with the MUSE instrument along with the telescope’s adaptive optics system, at one area of the sky for over 140 hours. Together, the two instruments are one of the most powerful systems in the world (3). The selected area is part of the Hubble Ultra-Deep Field, which was by far the deepest image of the cosmos ever found. However, Hubble has now surpassed it, as 40% of galleries found by MUSE are not against Hubble images.
After a detailed design, it took eight months to make this unique observation campaign. This was followed by a year of data processing and analysis, which for the first time revealed light from the hydrogen filaments, as well as images of several filaments as they were one to two billion years after the Big Bang, a prime time for understand how galaxies were formed from the gas in the cosmic web. However, the team ‘s biggest surprise was when symbols showed that the light from the gas came from an invisible population of billions of black galaxies emitting several stars (4). While these galaxies are too weak to detect on their own with conventional instruments, their survival will have a major impact for galaxy formation models, with an impact that scientists are not just beginning to study.
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Notes:
(1) MUSE, which stands for Mult-Unit Spectroscopic Explorer, is a 3D spectrograph designed to study the distant Universe. The construction of the instrument was directed by the Center de Recherche Astrophysique de Lyon (CNRS / Université Claude Bernard-Lyon 1 / ENS de Lyon).
(2) Other French laboratories involved: Laboratoire d’Astrophysique de Marseille (CNRS / Aix-Marseille Université / CNES), Institut de Recherche en Astrophysique et Planétologie (CNRS / Université Toulouse III – Paul Sabatier / CNES).
(3) See ESO Press Release 1 August 2017: https: /
(4) Until now, theory had predicted that the light came from diffuse cosmic ultraviolet background radiation (very weak background radiation produced by the galaxies and stars) which, with heating the gas in the filaments, causing them to glow.
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