This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A researcher from Sejong University has used a new theory of gravity proposed by Erik Verlinde to predict the observed central surface density of dark matter. The study was published in Physics of the Dark Universe on Sept. 20.
Since the 1970s, the rotation speeds of galaxies have been regarded as important observational evidence for the existence of dark matter. Stars in the outer regions of galaxies move much faster than would be expected if Newtonian gravity were applied to visible matter alone. In mainstream astronomy, this phenomenon is explained by assuming that galaxies are surrounded by invisible dark matter that provides additional gravitational attraction.
However, researchers have also continued trying to explain galactic dynamics by modifying the theory of gravity itself rather than invoking dark matter. In 1983, Mordehai Milgrom proposed that Newtonian gravity might need to be modified in regimes of very weak gravitational acceleration. In 2016, Verlinde proposed a new theory of gravity, known as "emergent gravity," aimed at explaining gravitational phenomena on galactic scales without assuming the existence of dark matter.
Meanwhile, astronomical observations have revealed an intriguing regularity: Even among galaxies whose luminosities differ by a factor of about 400,000, the "central surface density" of dark matter—defined as the product of the central dark matter density and the characteristic size of the central region—remains nearly constant, in the range of 90–220 M⊙/pc². In the new study, Youngsub Yoon applied Verlinde's theory of gravity to calculate the central surface density that would be inferred if dark matter were assumed to exist, obtaining a value of 170 M⊙/pc². The study uses a new relation Yoon proposed in 2024 while addressing a technical issue in Verlinde's theory of gravity.
Unlike Newtonian gravity, Verlinde's theory does not allow the gravitational effects produced by multiple masses to be simply added according to the usual superposition principle. Yoon proposed a relation to address this issue, and in the present study he used it to calculate the central surface density of dark matter in galaxies. "In my 2024 study, I pointed out a technical issue in Verlinde's theory of gravity and proposed a relation to address it.
It is meaningful that, in this study, the relation led to a result consistent with the actual observational value," Yoon said. "This study shows that a new theory of gravity that does not assume dark matter can explain yet another intriguing regularity observed in galaxies." Yoon added, "Professor Kyu-Hyun Chae of Sejong University has reported results from observations of wide binary stars that deviate from the predictions of Newtonian gravity in the very weak-gravity regime. I hope that this study, together with other research reexamining conventional theories of gravity in the weak-gravity regime, will contribute to testing new theories of gravity." Youngsub Yoon, A characteristic phantom-halo surface-density scale in Verlinde-inspired emergent gravity, Physics of the Dark Universe (2026).
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