The James Webb Space Telescope, which has not even completed its first full year of observations, has delivered truly astounding results. But in the middle of breathtaking pictures and unprecedented discoveries, there was a puzzling claim: that the telescope had detected galaxies in the incredibly young universe. These galaxies were so massive and appeared so early that they, according to the headlines, “broke” the big Bang cosmology model.
The claim has gone viral, but as with many things on the internet, it’s simply not true.
Now there is more research to back up the Big Bang. Recently, researchers took a closer look at the data and determined that the distant galaxies discovered by the James Webb Space Telescope are, indeed, perfectly compatible with our modern understanding of cosmology.
Related: The James Webb Space Telescope never disproved the Big Bang. Here’s how this lie spread.
The potential problem with distant galaxies is not that they exist. In fact, the modern formulation of the Big Bang theory, called ΛCDM cosmology (the Λ stands for dark energy, and CDM is short for “cold dark matter”), predicts the appearance of galaxies in the very young universe. This is because billions of years ago there was no galaxiesor even stars, at all. When our universe was much smaller and much denser than it is today, everything was much more uniform, with only tiny differences in density appearing here and there at random.
But over time, these density differences increased, with slightly denser pockets attracting more matter to them. Over hundreds of millions of years, these pockets formed in the first stars, and eventually grew to become the first galaxies.
In fact, one of the main purposes of the Webb telescope was to discover and characterize these first galaxiesso finding galaxies in the incredibly young universe is a point in service of the Big Bang theory, not against it.
So what is the conflict? The apparent tension arose because of the estimated masses of these galaxies. Several were quite large – well over 10^10 solar masses. It is still much smaller than the Milky Waybut for the early universe, they are quite gigantic.
The researchers who discovered these galaxies felt that their large masses put them in tension with many models of galactic formation and evolution. At the extreme, the researchers claimed that it might even be possible that no model of galaxy formation in the ΛCDM framework creates such large galaxies so quickly.
A subject of debate
But those claims relied on measuring an accurate distance to those galaxies — an incredibly difficult task at those extreme distances. For record galaxies that might be in tension with cosmological models, the researchers relied on something called a photometric redshift, which fits an approximate light spectrum from a galaxy to a model to estimate a distance.
This method is notoriously unreliable, with simple effects – like excess dust surrounding galaxies – making them appear farther away than they really are.
To accurately judge whether the Big Bang is in trouble, a new team of researchers has used Webb to identify galaxies with a much more precise and reliable method of determining distance known as spectroscopic redshift. This technique identifies the spectral lines of known elements emitted by galaxies and uses them to measure the red shiftand therefore the distance, to the galaxies.
Using this more precise technique, the team found a sample of four galaxies. All of these galaxies were just as distant as the previously identified galaxies, but they had confirmed and reliable distances. However, these galaxies had much smaller masses: around 10^8 and 10^9 solar masses.
The question then became, does ΛCDM allow these smaller galaxies to exist at such a young age in the history of the universe, or does the tension persist?
Then come the simulations
Building galaxies is not an easy task. While pen-and-paper mathematics can allow cosmologists to trace the overall history and evolution of the cosmos in the ΛCDM model, galaxy formation involves the complex interplay of many types of physics: gravitystar formation and supernova explosions, dust distribution, cosmic raysmagnetic fields and more.
Accounting for all of these interactions requires the use of supercomputer simulations that take the raw, primitive state of the universe as it was billions of years ago and follow the laws of physics to build artificial galaxies. This is the only way to connect what we see in the real world (galaxies) with the fundamental parameters of the ΛCDM model (like the amount of normal and black matter in the cosmos).
The simulations allowed the researchers to play with many types of models. If no model could generate galaxies of this mass at this age, then ΛCDM would be in trouble.
Fortunately, there were no such problems. The appearance of galaxies with 10^8 solar masses in the early universe was no sweat for ΛCDM, the team explained in their research paper, which has been submitted to The Astrophysical Journal Letters and is available for preprint via arXiv.
As usual, this is not the final answer. Astronomers could yet confirm the distance to a very large galaxy in the early universe, which could force us to rethink our understanding of galaxy formation, and perhaps even the ΛCDM cosmological model. In science, it is always important to keep an open mind. But the exaggerated claims made from Webb’s early data aren’t enough to worry about yet.
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