For the first time, astronomers have large-scale images of the cosmic web – the incredibly old scaffolding of dark matter and hydrogen gas that gave birth to galaxies in the Universe.
This material is so distant and so incredibly faint that it took one of the largest telescopes in the world in combination 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 was formed about 13.8 billion years in a sudden and colossal burst of expanding space and energy. In many ways it was like an explosion, although an explosion from space, no in space: it was the creation of the space itself. It was packed with energy and matter, and distribution did not go smoothly. In some places there was a little more matter than in others. These over- and under-populated areas were incredibly small; a typical denser spot may be 1 in 100,000 parts closer than its neighbor. But that was enough to create all the structure we see in the universe today.
These overly 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 with or emit light, but has mass and gravity – attracted material around it and began to form long, thin, interconnected filaments of material, like a web. “Normal” matter, the stuff we are made of, was drawn to and collected on these filaments. Gravity moved matter along the filaments, accumulating and forming galaxies, galaxy clusters and even immense superclusters, clusters of galaxy clusters, the largest shell structures in the known Universe.
All this due to small fluctuations in the structure of the room!
The problem is seeing this original structure, the original filaments that made up the cosmic web. They would be charged with hydrogen gas and glow, but this all happened so long ago that it took more than 13 billion years for the light from them to reach us. They are lameHowever, some success has been achieved in detecting it.
For example, quasars, intensely bright galaxies that emit radiation while their central supermassive black holes swallow matter, can be used to find them. As the quasar light passes through that original hydrogen gas, some of the light is absorbed in characteristic ways, and we can see that absorption in the quasar light. But that only shows you where that gas is in an extremely narrow spot in the sky, and even if you do this with hundreds of quasars, the map you get is literally spotty.
Some of that gas has also been seen glowing (what we say is in emission), but only near where bright galaxies illuminate it. Again, it is a very localized detection in a special location. What astronomers needed was a map of this material in typical places in the Universe, representative of 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 spot in the sky observed by Hubble to create the Ultra-Deep Field, an area of the sky that is about the same size. like a grain of sand an arm’s length away … but what Hubble oversaw 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 of deeper: over the course of 8 months, they took a whopping 140 hours of usable images in that one spot in the sky. And these weren’t just images, either. They took spectra and divided the light into separate 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 billions of years later, it has shifted red to the near infrared. By looking at the exact observed wavelength, the redshift and thus the distance to that LyA gas can be determined.
And what they found were long filaments of glowing hydrogen gas, some more than 13 billion light years away, structures emerged when the cosmos was less than a billion years old!
In fact, they found clumps and filaments 11.5 to 13+ billion light years away from Earth, some of which were more than 10 million light years long and only a few hundred thousand light years wide. They found more than 1,250 individual sites of LyA emission, some of which were grouped into 22 large overdense areas of LyA emission with between 10 and 26 different clumps in them. Those clumps represent galaxies and clusters in the very early stages of formation, not long after the formation of the universe itself.
It will be better. They also found a lot of faint LyA emission far beyond those clumps, which is called extensive emissionSimulations of the way matter clumped together in the very early days of the Universe indicate that this expanded emission is caused by the birth of billions of dwarf galaxies much smaller than our own Milky Way. These are called ultra-low light transmitters because they are extremely dim, some only a few thousand times the brightness of our sun. Given that the Milky Way is many billions of times brighter than the Sun, you can understand how dim these dwarf galaxies are, and how many of them there must be to illuminate that diffuse gas.
These galaxies are extremely young; we see the light of them when they were less than 300 million years old. Again, for comparison, the Milky Way is over 12 billion years old, so we see a bit of the Universe when it was practically a baby.
In addition, they found that of all their sources in the VLT / MUSE data, 30% were not seen in the Hubble Ultra Deep Field, meaning these are even fainter objects than Hubble could see. This is not surprising, given that VLT is much larger than Hubble and can capture more light. But it is still quite an achievement.
As an astronomer, I’m amazed that all of this was possible, let alone simulations of the way we think the early Universe would behave. That is a crucial point: using only mathematics, physics and observations of the sky we have been able to predict what the universe looked like when it was very young … and find out that we are right!
I hear people belittle science all the time, pooping the results as mere guesses. But it is in fact and in fact the best method we have for understanding objective reality, that which exists outside of us. It’s a phenomenally successful method, and these new observations are more evidence of it
You can deny science if you want to, but you go against the universe itself. You may want to think carefully about that position.