A combined use of the Hubble and Chandra space telescopes allowed to conduct a study of dark matter and the results were described in an article published in the journal “Science”. Currently we have no instruments to directly detect dark matter so scientists have to study it indirectly through its effects, in this case on 72 galaxy clusters to study their behavior.
This research was conducted in collaboration between the French École Polytechnique Fédérale de Lausanne (EPFL) and the Scottish University of Edinburgh. It’s one of many studies that are trying to shed light on one of the greatest mysteries of astrophysics in this beginning of the 21st century. Dark matter makes up most of the matter in the universe but we can say that it exists only because of its effects but don’t really know its nature.
Dark matter was called so because it doesn’t reflects, absorbs or emits light. However, it interacts with normal matter through the force of gravity and this allows to study it in an indirect manner and over the years even a map of its distribution was created.
In the case of this specific research, the scientists looked particularly at great cosmic collisions among galaxies. They occur during incredibly long times, even billions of years, with immense amounts of normal matter and especially dark matter that interact with each other due to the force of gravity.
In particular, the so-called effects of gravitational lensing, the distortion of light caused by the enormous gravity of one or more galaxies, allows to carry out precise studies on their total masses and characteristics. In the 72 galaxy clusters studied in the course of this research, collisions among galaxies occurred at different times and are visible at different angles.
The Hubble Space Telescope allowed to map the distribution of stars and dark matter after a collision, taking advantage of the effect of gravitational lensing on the background light. Chandra was used to detect the X-ray emission from the dust clouds that collided.
The team of researchers found that dark matter kept moving through the violent collisions without slowing down much. This means that dark matter interacts with itself less than previously thought. It’s just a piece of a mystery difficult to solve because it must be studied indirectly. The research on the infinitely large and infinitely small continue together to allow us to better understand some of the secrets of the universe.