An international team of astronomers has released an incredible new map of the distribution and movements of dark matter up to 2 billion light-years from Earth. The map was possible thanks to sophisticated computer modeling using indirect data.
“Dark matter is a substance of yet unknown nature that scientists believe makes up more than 80 percent of the total mass of the Universe,” lead author Dr Florent Leclercq, from the University of Portsmouth, said in a statement. "As it does not emit or react to light, its distribution and evolution are not directly observable and have to be inferred."
To infer the movement of dark matter, the new research, published in the Journal of Cosmology and Astroparticle Physics, used detailed maps of the distribution of galaxies. The data comes from eight years of observations from the Sloan Digital Sky Survey. It’s a large three-dimensional map of the universe, covering a fifth of the sky with data from over 900,000 galaxies.
Converting this wealth of data into a dark matter map is not trivial. The researchers used something called phase-space, where the properties of a physical state are mapped. In this specific map, the researchers plotted the position and velocities of dark matter, delivering a new view on the subject.
“Adopting a phase-space approach discloses a wealth of information, which was previously only analyzed in simulations and thought to be inaccessible using observations,” Dr Leclercq added. “Accessing this information in galaxy surveys opens up new ways of assessing the validity of theoretical models in light of observations.”
Dark matter remains a mysterious and controversial topic. It was first proposed decades ago to explain how galaxies rotate. Astronomers indirectly assessed its properties and began using it in models that turned out to agree well with observations.
Unfortunately, even after these successes, we have no evidence of its existence beyond any reasonable doubt. No particle of dark matter has ever been observed and even the most successful model, known as cold dark matter, has limitations. For example, it predicts the existence of hundreds of small galaxies orbiting the Milky Way, but we only see a few dozens at best.