Scientists Compile Largest Ever Catalog of Galaxy Clusters

Lebanon Today

In a move considered among the most important in modern astronomy, an international team of scientists has announced the preparation of the largest catalog of galaxy clusters ever, an ambitious project that could change our understanding of the “dark universe.”

The term “dark universe” refers to the mysterious part that makes up more than 95% of the content of the universe, including dark matter and dark energy, both of which are invisible but their effects are evident in observations using the most powerful telescopes.

Dark Energy Survey:

The team relied on data from the “Dark Energy Survey” project, a large-scale astronomical survey that lasted 6 years using the Dark Energy Camera mounted on the 4-meter “Blanco” telescope in Chile.

The camera collected images of the night sky showing galaxies 8 billion light-years away from us, and revealed tens of thousands of galaxy clusters, which are regions in the universe containing hundreds or thousands of galaxies linked by gravity, forming what resembles a string of light in a massive cosmic web.

The result was a three-dimensional map showing how matter has gathered over time, which is like a “growth fingerprint” of the universe since its inception after the Big Bang until today.

Galaxy Clusters:

Galaxy clusters are not just spectacular sights in the depths of space, but a natural laboratory for studying the laws of cosmic physics, as each cluster contains vast amounts of matter, visible and dark, which slows down the expansion in its regions due to gravity.

By analyzing the distribution of these clusters over time, scientists can test whether the universe is expanding according to current theoretical models or whether there are mysterious factors slowing down or accelerating the growth of cosmic structures.

The new data was examined according to what is known as the “Lambda CDM” model or the standard model of cosmology, which is the model that describes the universe as consisting of: about 70% of dark energy that drives the accelerated expansion of the universe, 25% of dark matter that maintains the cohesion of galaxies, and only 5% of ordinary matter that includes stars and planets, including us.

Tension of the Universe:

The results showed that what was observed from the clusters is almost consistent with what this model expects. In other words, the universe is still behaving as expected, at least within the limits of what can be observed currently.

Despite this conformity, there is still a mysterious signal that worries scientists, known as “S8 tension”, which is a slight difference between the extent of matter “clumping” that we observe today and what was expected based on the radiation of the ancient universe (which was observed by the Planck mission of the European Space Agency).

This tension may be just a statistical error, or it may be a sign of completely new physics, such as a different type of dark matter or dark energy that varies over time.

The matter will not stop here, as observatories such as Vera Rubin and the Nancy Grace Roman Space Telescope, which will be launched in the future, will begin to collect more accurate and deep data, and these tools will be able to observe billions of galaxies with unprecedented accuracy, which will allow for more decisive tests of the history of the expansion of the universe and the growth of galactic structures in it.