Placing Doubt on the Uniqueness of Dark Matter as an Invisible Component of Galaxies

11.11.2022

From the University of Padua, researcher Camilla Pianta and Department of Physics and Astronomy Professor Giovanni Carraro of the University of Padua publish the article The impact of binaries on the dynamical mass estimate of dwarfgalaxies together with Roberto Capuzzo Dolcetta of the University La Sapienza of Rome. The article considers a possible alternative to dark matter as a component of the satellite dwarf galaxies of the Milky Way which, being the oldest objects, retain the characteristics of the early universe which is believed to be dominated by the halos of dark matter.

A parameter called the mass-luminosity ratio tells us if dark matter exists inside dwarf galaxies. Such a parameter states that if a mass is greater than its luminosity, the system must have a mass that does not emit light. The absence of light means they are not made up of stars, hence the term dark matter. Whereas the visibility of stars within a star system of dwarf galaxies, especially if ultra-faint, is rare. Without sufficient light to measure, astronomers look towards another parameter, namely the motion of stars to detect the mass of a system.

On the other hand, the mass-luminosity ratio of ultra-faint galaxies can be calculated from the motion of their binary stars that are compatible with the observed mass value. This leads to the conclusion that the idea of the presence of binary stars as an alternative to dark matter explains why these galaxies are not observable by telescope, explained only in the case of ultra-faint galaxies, this places a "crack" of doubt about the uniqueness of dark matter as an invisible component of galaxies.