For the first time, astronomers have large-scale images of the cosmic web – the incredible ancient scaffolding of dark matter and hydrogen gas from which galaxies were formed in the universe.
This material is so far away and so incredibly faint that it has taken one of the largest telescopes in the world, along with one of the most powerful cameras to see it at all. But what they found in their images was the framework of the universe.
The universe formed about 13.8 billion years ago in a sudden and colossal eruption of expanding space and energy. In many ways it was like an explosion, although an explosion of space, not in space: it was the creation of space itself. It was chock full of energy and matter, and the distribution was not smooth. Some places matter a little more than others. These over- and under-covered regions were incredibly small; a typical denser place can be 1 part in 100,000 denser than the neighbor. But it was enough to create all the structures we see in the Universe today.
These excessive regions had enough gravity to overcome the expansion of the universe and collapsed. Dark matter – a still mysterious substance that does not react with or radiate light, but which has mass and gravity – attracted material around it and began to form long, thin, interconnecting material filaments such as a web. ‘Normal’ matter, the stuff we’re made of, was drawn to these filaments and collected on them. Matter flowed along the filaments due to gravity, and piled up and formed galaxies, clusters of galaxies, and even huge superclusters, clusters of galaxies, the largest scale structures in the known Universe.
All this through small fluctuations in the fabric of space!
The problem is to see this original structure, the original filaments that formed the cosmic web. They would be charged with hydrogen gas and glowing, but it all happened so long ago that it took over 13 billion years before the light came from us. They are faint. There is, however, success in locating them.
Quasars, intensely bright galaxies that emit radiation as their central supermassive black holes devour matter, for example. As the quasar light passes through that primordial hydrogen gas, some of the light is absorbed in characteristic ways, and we can see that the absorption is in the quasar light. But it only shows you where the gas is in an extremely narrow spot in the air, and even if you do it with hundreds of quasars, the map you get is literally spotlight.
Some of the gas was also seen glowing (what we say is ian emission), but only near where bright galaxies illuminate it. Again, this is a very localized detection in a special place. What astronomers needed was a map of this material in typical places in the universe, representing the cosmos as a whole.
And that’s what they have now. A few years ago, astronomers used the massive 8.2-meter Very Large Telescope (VLT) with the MUSE camera to look at the same place in the sky that Hubble observed to create the Ultra-Deep Field, a area of the same air. like a grain of sand that holds arm’s length … but which Hubble overlooked 10,000 galaxies.
When they observe this field with VLT / MUSE, they see a lot of hydrogen gas, and therefore they are encouraged to observe deeper. Many deeper: over the course of eight months, they took a staggering 140 hours of usable images at that single spot in the air. And it wasn’t just images either. They took spectra and broke up the light into individual colors. Hot hydrogen gas in the early universe glows with a characteristic color in the ultraviolet called Lyman-α (Lyman-alpha, or LyA for short). By the time this light reaches us billion years later, it has shifted red to near-infrared. By looking at the exact observed wavelength, the red shift and thus the distance to that LyA gas can be determined.
And what they found were long filaments of glowing hydrogen gas, some of which were more than 13 billion light years away, structures that formed when the cosmos was less than a billion years old!
They actually found clumps and filaments from 11.5 to 13+ billion light-years away from Earth, some of which are more than 10 million light-years long and only a few hundred thousand light-years wide. They found more than 1,250 individual sites where LyA was emitted, some of which were grouped into 22 large areas with LyA emission, which had between 10 and 26 distinct clusters. These clusters represent galaxies and clusters in the earliest stages of formation, not long after the creation of the universe itself.
It’s getting better. They also found very vague LyA emissions outside those lumps, which are called extended emissions. Simulations of the way matter was put together in the early days of the Universe indicate that this extensive emission is caused by the birth of billions of dwarf systems, much smaller than our own Milky Way. It’s called ultra-low brightness emitters because they are extremely faint, some only a few thousand times the brightness of our sun. Since the galaxy is many billions of times brighter than the sun, you can realize how flimsy these dwarf systems are and how much there must be to ignite the diffuse gas.
These galaxies are very young; we see the light of them when they were less than 300 million years old. Again, by comparison, the Milky Way is more than 12 billion years old, so we see a part of the universe when it was virtually a baby.
In addition, they found that 30% of all their resources in the VLT / MUSE data were not seen in the Hubble Ultra Deep Field, meaning that they are even duller objects than Hubble could detect. This is not very surprising, as VLT is much larger than Hubble and can collect more light. But it’s still the achievement.
As an astronomer, I am surprised that it was even possible, let alone that it corresponds to simulations of the way we think the early universe would behave. This is a critical point: using only math, physics, and aerial observations, we were able to predict what the universe was like when it was very young … and find that we are right!
I hear people denigrating science all the time, and only guessing the results of poop-pooing. But it is in fact and in fact the best method to understand objective reality, that which exists outside of us. It’s a phenomenally successful method, and these new observations are more proof of that.
You can deny science if you want to, but you are going against the universe itself. You may want to think carefully about this position.