An international team of researchers, which includes UvA physicist Gianfranco Bertone, has obtained the first observational proof of the presence of dark matter in the innermost part of the Milky Way, where our own planet is located. Their results were published today online in the journal ‘Nature Physics’.
The universe is pervaded by invisible dark matter, which is about five times more abundant than the ‘ordinary matter’ comprised of atoms. Its existence in galaxies was 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 mass.
This technique can also be applied to our own Galaxy. Although the existence of dark matter in the outer parts of the Milky Way is well established, it has historically proven very difficult to confirm the existence of dark matter within the innermost regions, where the solar system is located, due to the difficulty of measuring the rotation of gas and stars with the needed precision.
Bertone – with co-authors Fabio Iocco of the ICTP South American Institute for Fundamental Physics and Miguel Pato of Stockholm University – created the most complete compilation of published measurements of the motion of gas and stars in the Milky Way, and compared the measured rotation speed with that expected under the assumption that only luminous matter exists in the Galaxy. Their findings demonstrate that the observed rotation cannot be explained unless large amounts of dark matter exist around us, and between us and the galactic centre.
Gianfranco Bertone, spokesman for the GRAPPA research priority area: ‘We anticipate that our results will lead to further developments in astroparticle physics and cosmology. With new upcoming astronomical observations, our method will allow us to measure the distribution of dark matter in our Galaxy with unprecedented precision. This will refine our understanding of the structure and evolution of our Galaxy, and it will trigger more robust predictions for the many experiments worldwide that search for dark matter particles. Our study therefore constitutes a fundamental step forward in the quest for the nature of dark matter.’
Fabio Iocco, Miguel Pato and Gianfranco Bertone: ‘Evidence for dark matter in the inner Milky Way.’ Nature Physics (online publication 9 February). DOI: 10.1038/NPHYS3237