In a pioneering find, a team of scientists has obtained a direct observational proof of the presence of dark matter in the innermost part of the Milky Way, including at the Earth's location and in our own "cosmic neighbourhood".
"We know that dark matter is needed in our Galaxy to keep the stars and gas rotating at their observed speeds," said Miguel Pato who conducted the analysis at Technische Universitat Munchen (TUM).
However, we still do not know what dark matter is composed of. This is one of the most important science questions of our times, he added.
The ubiquitous presence of dark matter in the universe is today a central tenet in modern cosmology and astrophysics.
Its existence in galaxies was robustly established in the 1970s with a variety of techniques, including the measurement of the rotation speed of gas and stars, which provides a way to effectively 'weigh' the host galaxy and determine its total mass.
These measurements showed that the visible matter only accounts for a fraction of the total weight, the predominant part is delivered by dark matter.
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For the new study, the team created the most complete compilation of published measurements of the motion of gas and stars in the Milky Way.
Then they compared the measured rotation speed with that expected under the assumption that only luminous matter exists in the Galaxy.
The comparison clearly showed that the observed rotation cannot be explained unless large amounts of dark matter exist around us, and between us and the galactic centre.
"The findings will refine the understanding of the structure and evolution of our Galaxy. It will also trigger more robust predictions for the many experiments worldwide that search for dark matter particles," said Miguel Pato from the Oskar Klein Centre for Cosmoparticle Physics at Stockholm University.