An image captured by the Dark Energy Camera (DECam) depicts the Coma Cluster, also known as Abell 1656, so named because it’s part of the constellation Coma Berenices. DECam was designed to conduct a long-term investigation of dark energy but is also useful for other types of astronomical studies. The Coma Cluster is linked to the study of dark matter since the inconsistency between the estimate of its overall mass and the measurement of its gravitational effects stimulated the research that led to today’s dark matter models.
It was 1933 when the Swiss astronomer Fritz Zwicky estimated the total mass of the Coma Cluster based on the bright objects he had observed within it. However, the gravitational effects measured in that cluster indicated that it contained an amount of matter that Zwicky indicated in an article (in German) published in the journal “Helvetica Physica Acta” in about 400 times greater than what he had estimated. For that reason, he hypothesized that the galaxies were held together by something he called dark matter.
At the time, Fritz Zwicky’s study was greeted with skepticism but in the following decades, other astronomers began to notice the same type of inconsistency, even at the level of single galaxies. For example, that was detected in the Andromeda galaxy in the study conducted by the American astronomers Kent Ford and Vera C. Rubin in 1970.
Today the expression dark matter used by Fritz Zwicky has become common and there are various models that try to explain those gravitational effects. Most of those models are based on the existence of dark matter, which is supposed to be made of particles different from those of baryonic matter, that is, ordinary matter. However, attempts to detect these particles have failed so far, leading to the development of alternative models that explain the gravitational effects attributed to dark matter in different ways.
The still mysterious aspects of dark matter make it essential to continue observations at the level of galaxies and galaxy clusters. The Coma Cluster remains a significant object of study for this type of research even after having been observed on many occasions over the decades.
The DECam, installed at the Cerro Tololo Inter-American Observatory (CTIO), Chile, was designed to conduct an investigation of dark energy and therefore the expansion of the universe. It captures very detailed images, which are also useful for testing the various models of dark matter and alternative ones. Studies continue with other instruments as well, which in the future will include the Vera C. Rubin Observatory, named after the astronomer who contributed to this type of cosmological studies.
