The James Webb Space Telescope, which hasn’t even finished its first full year of observations, has produced some real wonders. But in the middle of awesome images and unprecedented findings, 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, according to headlines, they “broke” the big Bang cosmology model.
The claim went 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. Researchers recently took a closer look at the data and determined that the distant galaxies discovered by the James Webb Space Telescope are, in fact, perfectly compatible with our modern understanding of cosmology.
Related: The James Webb Space Telescope never disproved the Big Bang. This is how that falsehood 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 (Λ stands for dark energy, and CDM is short for “cold dark matter”), predicts that galaxies will appear in the very young universe. That’s because billions of years ago, there was no galaxiesor even stars, absolutely. When our universe was much smaller and much denser than it is today, everything was much more uniform, with only small differences in density appearing here and there at random.
But over time, those density differences grew, and slightly denser pockets drew more material onto them. Over hundreds of millions of years, these pockets formed in the first stars and eventually grew to become the stars. first galaxies.
In fact, one of the main objectives of the Webb telescope was discover and characterize those first galaxiesso finding galaxies in the incredibly young universe is a point in favor of the Big Bang theory, not against it.
So what is the conflict, then? The apparent tension occurred due to the estimated masses of those galaxies. Several were quite large, over 10^10 solar masses. That is still much smaller than the Milky Waybut for the early universe, they are quite gigantic.
The researchers who discovered these galaxies estimated that their large masses put them in tension with many models of galaxy formation and evolution. At the extreme extreme, the researchers claimed that it might not even be possible for any galaxy formation model within the ΛCDM framework to create such large galaxies so quickly.
a topic of discussion
But those claims depended on measuring a precise distance to those galaxies, an incredibly difficult task at these 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 spectrum of light from a galaxy to a model to estimate a distance.
That method is notoriously unreliable, with simple effects such as excess dust surrounding galaxies making them appear more distant than they really are.
To accurately judge whether the Big Bang is in trouble, a new team of researchers used Webb to identify galaxies with a much more accurate 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 redshiftand therefore the distance, to the galaxies.
Using this more precise technique, the team found a sample of four galaxies. All of these galaxies were as distant as previously identified galaxies, but had reliable and confirmed distances. However, these galaxies had much smaller masses: around 10^8 and 10^9 solar masses.
The question then became whether ΛCDM allows these smaller galaxies to exist at such an early age in the history of the universe, or does the tension remain?
the simulations arrive
Building galaxies is not an easy task. While paper-and-pencil mathematics may allow cosmologists to trace the overall history and evolution of the cosmos within the ΛCDM model, galaxy formation involves the complex interplay of many kinds of physics: gravitystar formation and supernova explosions, dust distribution, cosmics raysmagnetic fields and more.
Accounting for all these interactions requires the use of supercomputer simulations that take the raw, primal state of the universe as it was billions of years ago and follow the laws of physics to build artificial galaxies. That is the only way to connect what we see in the real world (galaxies) with the fundamental parameters of the ΛCDM model (such as the amount of normal and dark matter in the cosmos).
The simulations allowed the researchers to play with many types of models. If no model could generate galaxies of that mass at that 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 posed no problem for ΛCDM, the team explained in their research paper, which was submitted to The Astrophysical Journal Letters and is available as preprint via arXiv.
As usual, this is not the final answer. Astronomers can yet confirm the distance to a very large galaxy in the early universe which may 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 are still not enough to cause concern.
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