Apr 30 2019
A study led by SISSA has verified one of the latest and most spellbinding controversies on the most extensive form of matter in the universe and explains its connection with ordinary matter. Matter of this type does not emit any type of electromagnetic radiation.
(Image credit: SISSA)
Dark matter is as intriguing as it is obscure; it is one of the greatest riddles of cosmology and astrophysics. Although it is considered to constitute nearly 90% of the matter in the universe, its existence has been shown only indirectly and recently debated.
The new study performed at SISSA eliminates the recent uncertainties on the existence of dark matter inside the galaxies, thereby invalidating the empirical relations that support alternative theories. The research, reported in The Astrophysical Journal, also provides a new understanding of the nature of dark matter and its bond with ordinary matter.
There are various phenomena, such as the expansion of the universe to the movement of stars in the galaxies, which cannot be explained by the existence of ordinary matter alone, namely, the one composed by atoms. The attractive force produced by it is inadequate, leading to the theory of the presence of dark matter, which is undetectable, and the concept that galaxies are integrated into its spherical halo.
Three years ago, a few colleagues of the Case Western Reserve University strongly questioned our understanding of the universe and the in-depth work of many researchers, casting doubt on the existence of dark matter in the galaxies. Analysing the rotation curves of 153 galaxies, principally the ‘classical’ spiral kind, they obtained an empirical relationship between total gravitational acceleration of the stars (observed) and the component which we would observe in the presence of sole ordinary matter in the classical Newtonian theory. This empirical relationship which seemed valid in all the galaxies they analysed and at any galactic radius, motivated the explanation of gravitational acceleration without necessarily calling into question dark matter, but involving for example theories of modified gravity such as MOND (Modified Newtonian Dynamics).
Chiara Di Paolo, Doctoral Student of Astrophysics, SISSA.
Di Paolo and her colleagues intended to confirm this bond by investigating the rotation curves of galaxies apart from the “classical” spiral kind: 34 dwarf disk galaxies and 72 galaxies with low surface brightness (LSB). They generated more extended outcomes, leading to a relationship, which, apart from total gravitational acceleration and its ordinary component, also includes the morphology of the galaxies and the galactic radius.
We have studied the relationship between total acceleration and its ordinary component in 106 galaxies, obtaining different results from those that had been previously observed. This not only demonstrates the inexactness of the empirical relationship previously described but removes doubts on the existence of dark matter in the galaxies. Furthermore, the new relationship found could provide crucial information on the understanding of the nature of this indefinite component.
Paolo Salucci, Professor of Astrophysics, SISSA.
Salucci is one of the research authors of the study.