'Russian Doll Cluster': Measuring the expansion of the universe

© NASA / Reuters
If NASA’s Chandra X-ray Observatory, the European Space Agency's Planck and a slew of optical telescopes’ findings are too much to comprehend, the “Russian doll cluster” model may help to explain dark energy, dark matter and the expansion of the universe.

X-ray emissions from more than 300 galaxy clusters were studied by researchers from the University of Alabama in Huntsville to figure out how dark matter and dark energy operate, or the rate at which the universe is expanding.

Because galaxy clusters' X-ray emissions are similar in structure and size, their relationship to one another is akin to that of Russian dolls. By using the clusters as a point of reference, scientists are able to determine the rate at which they expanded.

“The nature of dark energy is one of the biggest mysteries in physics, so it’s crucial to invent new tools for studying its properties, since different methods can have very different assumptions, strengths and weaknesses,” said lead cosmologist on the study, Andrea Morandi in a NASA statement. “We think this new technique has the ability to provide a big leap forward in our understanding of dark energy.”

Morandi sat down with RT’s Manila Chan to share more.

“We observed a sample of 300 galaxy clusters, in order to understand the rate of the expansion of the universe. So, the idea was that we use these galaxy clusters like a kind of cosmic buoys,” referring to anchored flotation devices used for navigating ocean waters.

“You can imagine the universe like a sea,” Morandi continued, “and you can understand whether this sea of the universe is agitated or not by observing the movement of these buoys, or galaxy clusters, and this is the method we use to measure the expansion rate of the universe.”

The Russian doll analogy is drawn from the “different galaxy clusters, different sizes, but they can be thought like scaled version,” Morandi explained to RT. “For example, among humans, I could be thought like a scaled version of a 4-year-old boy. I have two arms, two legs, one head. We basically look similar, because of our DNA.”

“Something along the same line happens for galaxy clusters. In the case of galaxy clusters, the DNA is beautiful physical properties which is called dark matter.”

"This model is strongly entangled with the underlying cosmology. By measuring the physical properties of the galaxy cluster of the different distances from Earth, we can constrain, and by assuming our model of Russian doll clusters, we can measure very precisely the expansion rate of the universe," Morandi expounded.

"You can think about dark energy like repulsive energy, which is pushing away the universe, causing the expansion to accelerate. We don't really feel the effect of dark energy on Earth, but we can witness how the universe is expanding and accelerating on a large scale by studying these objects, galaxy clusters," Morandi said.