A breakthrough has emerged in the world of astrophysics as scientists studying dark matter have received their first transmission from deep underground. This brings us a step closer to unveiling the mysteries surrounding dark matter and its significance to the nature of the universe.
What is Dark Matter?
Dark matter refers to the component of the universe whose presence is perceived from its gravitational attraction rather than its luminosity. This mysterious and elusive material makes up about 23% of the mass-energy of the universe and is around five times as much as the matter that we can see.
Originally known as the "missing mass", dark matter was first conceptualized by Swiss American astronomer Fritz Zwicky. He discovered that the mass of all the stars in the Coma cluster of galaxies provided only around one percent of the mass required to keep the galaxies from escaping the gravitational pull of the cluster.
Since the confirmation of the existence of dark matter, its prevalence in galaxies has been understood through gravitational lensing. Other methods such as modifications to gravity have also been proposed to explain the presence of "missing matter".
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Going Deep in Search of Dark Matter
In studying the mysteries of dark matter, astronomers focus on the nature of muons, or the heavier versions of electrons made from the collision of cosmic rays with atoms in Earth's atmosphere. These collisions are recorded by muon detectors which determine the levels of cosmic radiation.
In Victoria, Australia, a muon detector was placed 0.62 mi (1 kilometer) underground in the Stawell Underground Physics Laboratory (SUPL). It records the amount of cosmic radiation that reaches the facility in Stawell Gold Mines.
SUPL will be the location of a dark matter direct-detection experiment called SABRE (Sodium-iodide with Active Background Rejection). This experiment aims to look for the hypothesized type of particle which may constitute dark matter. It is scheduled to be transported to the laboratory in 2024.
It is important that low levels of radiation are recorded to make sure that the environment surrounding the SABRE South experiment is as intact as possible to locate particles of dark matter. In its first few days, the muon detector recorded about five detections per day which is far lower than the 1.8 million interactions expected above the ground.
The first data collection showed that by building the laboratory one kilometer underground in Stawell Gold Mine, the research team can manage to reduce the cosmic radiation which will reach their dark matter detector.
CDM Director Professor Elisabetta Barberio reported that the data collection is an exciting milestone for the project. SUPL Chair Sue Barrell also claims that the milestone paved the way for scientific innovations in the future. This means that they are finally able to read the cosmic radiation levels deep underground while sitting at their desks at Melbourne University.
ARC Center of Excellence for Dark Matter Particle Physics (CDM) scientists plan to continue monitoring the levels of radiation before transporting the SABRE South experiment vessel into SUPL. The experiment mirrors a study in the Northern Hemisphere and will determine whether readings obtained by the researchers are a result of seasonal fluctuations, or dark matter.
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