hubble deep field
Hubble eXtreme Deep Field "XDF" (2012) view — except for a few stars, every speck of light is an entire galaxy — some as old as 13.2 billion years. NASA; ESA; G. Illingworth, D. Magee, and P. Oesch, University of California, Santa Cruz; R. Bouwens, Leiden University; and the HUDF09 Team

Dark matter — the mysterious stuff that we know is there, but have no clue what it’s made of. This is because despite accounting for roughly 85 percent of the universe’s mass, dark matter is invisible — it does not absorb, reflect or emit any light.

While most scientists believe that even though we have been unable to detect it just yet, dark matter does exist, and that it is responsible for the violations of Newtonian gravitational theory observed in the rotation of galaxies, there are some who have raised doubts over its existence. Some of those belonging to the latter of the two groups have suggested that the anomalies in the motion of stars and galaxies can be explained solely through a theory of “modified gravity.”

However, in a study published in the latest edition of the journal Physical Review Letters, a team of researchers has argued that the existence of dark matter is consistent with the observed relationship between mass, size and luminosity of galaxies. The study, based on supercomputer simulations that modeled the behavior of galaxies over billions of years of cosmic evolution, shows that the presence of dark matter can explain the diverse population of galaxies in the present-day universe.

“This solves a long-standing problem that has troubled the dark matter model for over a decade,” study lead author Aaron Ludlow from U.K.’s Durham University said in a statement. “The dark matter hypothesis remains the main explanation for the source of the gravity that binds galaxies. Although the particles are difficult to detect, physicists must persevere.”

According to the Lambda Cold Dark Matter (Lambda-CDM) model, which is the framework that governs our current understanding of the origin and evolution of the universe, dark energy and dark matter make up nearly 95 percent of the cosmos. Dark energy, which is an as-of-yet undetected force that comprises 68 percent of the universe, is believed to be responsible for its accelerated expansion, while dark matter is envelops galactic disks in the form of halos that give the galaxies most of their mass.

“All of our galaxies follow closely a simple relationship between the total and baryonic acceleration profiles, consistent with recent observations of rotationally supported galaxies,” the researchers wrote in the study. “These observations, consistent with simple modified Newtonian dynamics, can be accommodated within the standard cold dark matter paradigm.”

While the study bolsters the case for the existence of dark matter, it does not bring us any closer to discovering exactly what it is. Although scientists believe dark matter is made of either axions — a class of extremely light particles whose existence is predicted by an extension of quantum chromodynamics — or Weakly Interacting Massive Particles, which are heavy particles that interact with normal matter only through gravity and the weak nuclear force, no such particles have yet been detected.