Acidity is caused by protons (H+) which are rather strongly bonded to carrier molecules of the solvent, but still display mobility and activity. In aqueous solutions acidity is limited by the carrier cation H3O+. The same holds true for superacids in which the proton is bonded to molecules, which allow higher activity. Superacidity starts in a region around 1012 higher than the strongest acidic aqueous solutions. The number of superacids is rather small and acidity regions of around 1027 stronger than acidic aqueous solutions have been achieved. The general question about the limits of acidity that can be reached in a laboratory is not answered yet. However, the strongest acidic media in the universe are represented by the hydrogen plasma of stars and solar winds, both containing free protons. The theoretical limit of acidity is predicted to be in the region of 1056 stronger than acidic aqueous solutions.
Highly reactive ions, especially protonated intermediates, occurring in chemical reactions, technical processes, as well as in the interstellar space, are the main topic of our research. Our goal is the preparation and isolation of such elusive species using superacids and low-temperature methods.
 A. J. Kornath, Nachrichten aus der Chemie, 2008, 56, 1125-1129, and citations therein. https://doi.org/10.1002/nadc.200858015