For the first time, astronomers have obtained large-scale images of cosmic network – the incredibly old scaffolding of dark matter and hydrogen gas from which galaxies in the Universe 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 space and expanding energy. In many ways it was like an explosion, albeit an explosion of space, no in the space: It was the creation of space itself. It was full of energy and matter, and the cast was not smooth. Some places had less matter than others. These over- and under-dense regions were incredibly small; a typical denser point could be a part of 100,000 denser than its neighbor. But that was enough to create the whole structure we see in the Universe today.
These over-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 network. The “normal” matter, the things we are made of, was drawn to these filaments and gathered on them. Matter flowed along the filaments due to gravity, piling up and forming galaxies, groups of galaxies and even huge superclusters, groups of groups of galaxies, the largest scale structures in the known universe.
All this due to small fluctuations in the fabric of space!
The problem is to see this original structure, the original filaments that formed the cosmic network. They will be charged with hydrogen gas and glow, but all this happened so long ago that it took over 13 billion years for the light from them to reach us. They are weak. However, there was some success in detecting them.
To find them, for example, can be used quasars, strongly bright galaxies that radiate radiation, while their central supermassive black holes swallow matter. As quasar light passes through that primordial hydrogen gas, some of the light is absorbed in characteristic ways and we can see that absorption in quasar light. But that only shows you where the gas is in an extremely narrow place in the sky, and even if you do this with hundreds of quasars, the map you get is literally inappropriate.
Some of this gas has also been seen brilliantly (what we say is in broadcast), but only near the place where light galaxies ignite 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 (VLT) telescope with the MUSE camera to look at the same point in the sky observed by Hubble to create the ultra-deep field, an area of the sky the same size as a bean. of sand kept at arm’s length … but in which 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 take deeper observations. A lot deeper: over 8 months they took an amazing 140 hours of usable images on that single point in the sky. And these were not just images either. They took spectra, dividing the light into individual colors. The hot hydrogen in the early universe shines in a characteristic ultraviolet color called Lyman-α (Lyman-alpha, or LyA for short). Until this light reaches us billions of years later, it shifts to near-infrared red. Looking at the exact wavelength observed, one can determine the redshift and therefore the distance to that LyA gas.
And they found long filaments of bright hydrogen gas, some of them over 13 billion light years away, structures that formed when the cosmos was less than a billion years old!
In fact, they found agglomerations and filaments 11.5 to 13+ billion light-years away from Earth, some of them over 10 million light-years long and only a few hundred thousand light-years wide. They found more than 1,250 individual places where LyA was emitted, some of which were grouped into 22 large over-density regions of LyA emissions that had between 10 and 26 distinct agglomerations in them. Those agglomerations represent galaxies and groups in the early stages of formation, not long after the formation of the Universe itself.
She’s getting better. They also found a lot of unclear LyA emissions outside these agglomerations, which is called extended emission. Simulations of how matter agglomerated in the early days of the Universe indicate that this extensive emission is caused by the birth of billions of dwarf galaxies, much smaller than our own Milky Way. These are called very low light emitters because they are extremely faint, some only a few thousand times the brightness of our Sun. Given that the Milky Way is billions of times brighter than the Sun, you can appreciate how weak these dwarf galaxies are and how many of them need to be to ignite that diffuse gas.
These galaxies are extremely young; we see the light from 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 slice of the Universe when it was practically a child.
In addition, they found that of all their VLT / MUSE data sources, 30% were not seen in Hubble’s ultra-deep field, which means they are even weaker objects than Hubble could see. Not surprisingly, the VLT is much larger than Hubble and can collect more light. But it is still a great achievement.
As an astronomer, I am amazed that all of this was even possible to do, let alone find that it matches simulations of how we believe the early universe would behave. This is a critical point: using only mathematics, physics, and sky observations, we were able to predict what the Universe was like when it was very young people … and find out we’re right!
I hear people who denigrate science all the time, the results can be like simple assumptions. But it is actually the best way we have to understand objective reality, what exists outside of us. It is a method of phenomenal success, and these new observations are further evidence of this
You may reject science if you wish, but you are confronted with the Universe itself. You may want to think carefully about this position.