For the first time, astronomers have obtained large – scale images of the cosmic web – the incredibly ancient scaffolds of dark matter and hydrogen gas from which the galaxies of the Universe were formed.
This material is so far away and so incredibly faint that it took one of the largest telescopes in the world along with one of the most powerful cameras to see it. But what they found in their images was the very frame of the Universe.
The Universe formed about 13.8 billion years ago in a sudden and colossal explosion of expanding space and energy. In many ways it was like an explosion, albeit an explosion of space, no inside space: it was the creation of space itself. It was full of energy and matter, and the distribution was not fluid. Some places had a little more matter than others. These excessively and sparsely dense regions were incredibly small; a typical denser point could be 1 part per 100,000 denser than its neighbor. But that was enough to create the whole structure we see in the current Universe.
These too dense regions had enough gravity to overcome the expansion of the Universe and began to collapse. Dark matter, a still mysterious substance that does not react or emit light, but has mass and gravity, attracted material around it and began to form long, thin filaments of material, like a net. The “normal” matter, of which we are made, crawled towards these filaments and was collected on them. Matter flowed along the filaments due to gravity, accumulating and forming galaxies, galaxy clusters, and even immense superclusters, clusters of galaxy clusters, the largest scale structures in the known Universe. .
All this for small fluctuations in the fabric of the space!
The problem is to see this original structure, the original filaments that formed the cosmic network. They would be charged with hydrogen gas and glow, but all this happened so long ago that it has taken more than 13 billion years for light to reach us. They are weak. However, there has been some success in detecting them.
To find them, for example, you can use quasars, intensely bright galaxies that burst into radiation as their central supermassive black holes swallow matter. As quasar light passes through this primordial hydrogen gas, some of the light is characteristically absorbed and we can see this absorption in quasar light. But this only shows you where this gas is at an extremely narrow point in the sky, and even if you do this with hundreds of quasars, the map you get is literally uneven.
Some of this gas has also looked bright (what we say is andn issue), but only near where bright galaxies illuminate them. Again, it is a very localized detection in a special place. What astronomers needed was a map of this material in typical places in the universe, representative of the cosmos in general.
And that’s what they have now. A few years ago, astronomers used the massive 8.2-meter massive telescope (VLT) with the MUSE camera to look at the same point in the sky that Hubble observed to create the ultra-deep field, an area of the sky. the same size as a grain of sand at arm’s length … but in what Hubble saw 10,000 galaxies.
When they observed this field with VLT / MUSE they saw a lot of hydrogen gas, so they were encouraged to make deeper observations. A lot deeper: over eight months they took an astonishing 140 hours of usable images at that point in the sky. And they weren’t just images. They took spectra, dividing the light into individual colors. The hot hydrogen gas at the beginning of the Universe shines to a characteristic color of the ultraviolet called Lyman-α (Lyman-alpha, or LyA in short). When this light reaches us a billion years later, it shifts to red to the near infrared. By observing the exact wavelength observed, the redshift and therefore the distance to the LyA gas can be determined.
And what they found were long strands of bright hydrogen gas, some over 13 billion light years away, structures that formed when the cosmos was less than a billion years old.
In fact, they found clusters and filaments between 11.5 and 13 billion light-years away from Earth, some of them more than 10 million light-years long and only a few hundred thousand years old. light. They found more than 1,250 individual points where LyA was emitted, some of which were grouped into 22 large excessive regions of LyA emission that had between 10 and 26 different groups. These groups represent galaxies and clusters in the early stages of formation, shortly after the formation of the Universe itself.
Improvement. They also found many blurred emissions of LyA outside of these groups, so to speak extended broadcast. Simulations of how matter was grouped in the early days of the Universe indicate that this widespread emission is caused by the birth of billions of dwarf galaxies, much smaller than our Milky Way. These are called ultra low brightness emitters because they are extremely faint, some only a few thousand times the brightness of our Sun. Given that the Milky Way is many millions of times brighter than the Sun, you can see how weak these dwarf galaxies are and how many there must be to illuminate this diffuse gas.
These galaxies are extremely young; we see the light of them when they were less than 300 million years old. Again, by comparison, the Milky Way is over 12 billion years old, so we’re looking at a portion of the Universe when it was practically a baby.
On top of all that, they found that of all their sources in the VLT / MUSE data, 30% were not seen in the ultra-deep Hubble field, meaning they are even weaker objects than Hubble could detect. This is not at all surprising, as the VLT is much larger than the Hubble and can accumulate more light. But it is still quite a success.
As an astronomer, I am amazed that all of this is possible, even if I find that it matches simulations of how we think the primitive Universe would behave. This is a critical point: using only mathematics, physics and observations of the sky, we have been able to predict what the Universe was like when it was a lot young man … and check that we are right!
I feel people denigrating science all the time, poo-pooing the results as mere conjecture. But it is in fact and in fact the best method we have for understanding objective reality, that which exists outside of us. It is a phenomenally successful method, and these new observations are further proof of that
You can deny science if you want, but go against the universe itself. You may want to think carefully about this position.