One of the hydrogen filaments (in blue) discovered by MUSE in the Hubble Ultra-Deep Field. it is … [+]
Roland Bacon / David Mary / ESO / NASA
Out there in the cosmos are billions of galaxies, but they are not in random places no matter where you look. They form on, and are connected by, long fibers or filaments of hot gas.
That has long been predicted by cosmological models, but for the first time astronomers have seen these filaments directly.
In doing so, astronomers using ESO’s Very Large Telescope (VLT) in Chile have unveiled a “cosmic web” that shows a hitherto invisible population of billions of black galaxies.
In addition, the image was the result of marking the VLT at the same piece of the night sky that was used to produce the Hubble Ultra-Deep Field, which had hitherto been the deepest image of the cosmos ever found. It is also one of the most studied space fields.
This new image – the result of 140 hours of telescope time – surpasses the Hubble-marked image by featuring an additional 40% of galaxies not seen in Hubble images.
The original Hubble Ultra Deep Field image. He had to take over 800 800 appearances … [+]
NASA, ESA, S. Beckwith (STScI) and HUDF Team
The imaging was made possible after instrument improvements on the VLT called the Multi Unit Spectroscopic Explorer (MUSE), which made a similar effort in 2017. MUSE is designed to look at complete celestial objects in 3D.
It is used to study the early Universe, when the first stars and galaxies formed; these new ideas of the first Universe are between one and two billion years after the Big Bang.
This “cosmic web” – the filamentary structure of hydrogen gas in which galaxies form – is one of the main predictions of the Big Bang and the galaxy formation models.
Cosmological simulation of the distant Universe. The image shows the light emitted by hydrogen atoms … [+]
Jeremy Blaizot / projet SPHINX
“Imagining the cosmic web – the diffuse distribution of gas between galaxies, and not just the brightest galaxies – has been the ‘pride’ of the extragalactic community for 40 years,” said Roland Bacon, research professor at the French National Scientific Research Center (CNRS), designer of the MUSE project and first author of the new paper published today in the journal Astronomy & Astronomy.
“For a long time, it wasn’t easy to get to this grip because it was beyond our observation abilities.”
Hubble prefers MUSE by dividing up the light from each point in the image to its complementary colors to create a spectrum. That allows astronomers to measure the distance, colors and other features of all the galleries they see, including some that are invisible to Hubble.
It was built under the direction of CNRS, MUSE live in 2014 and was connected to VLT’s adaptive optical system in 2017.
Adaptive optics use lasers to create a false star for the VLT to focus on, largely correcting for the glare effects of the Earth’s turbulent atmosphere. It basically allows much clearer images.
View of one of the VLT (Very Large Telescopes) in Paranal, some 1150 km north of Santiago, Chile on … [+]
AFP through Getty Images
“I realized that for the first time we might have the performance to test those ideas,” Bacon said. Asking the VLT to look at one field in the sky for more than 140 hours of observation was a huge gamble, ”he said, and took eight months of careful planning.
A year of data and signal processing and analysis followed. “In the midst of a pandemic, I was able to devote myself almost full-time to this analysis,” Bacon said. “We realized that the diffuse scattering did not come from a UV cosmic background, as would be expected, but from a previously invisible population with many small galaxies.”
The newly revealed galaxies in the image are too weak to be detected alone with conventional telescopes, but the presence of a galaxy model will have a major impact, say the authors.
Wishing you clear skies and wide eyes.