Dark Energy is a subset of energy that accelarates the expansion of our universe. A new research work at FIAS studies the impact of dark energy inside our galaxies. The research shows that in order to have stable galaxies the repulsion force of dark energy cannot exceed two orders of magnitde of the known value from cosmology. This study suggests that dark energy plays a role stronger than expected even in the closeby universe.

The universe is shaped by two mysterious forces: dark matter, which attracts and pulls galaxies together, and dark energy, which repels and drives them apart, causing the universe to expand. Dark matter accounts for about 26% of the universe's energy, while dark energy makes up roughly 68% (the other 6% are the known baryonic matter that we and the stars are made of ). These forces, one attractive and the other repulsive, have long been considered the primary influences on the structure and evolution of the cosmos.

New research by David Benisty and David Vasak from the groups of FIAS Fellows Jürgen Struckmeier and Horst Stöcker from the Frankfurt Institute for Advanced Studies (FIAS) suggests that dark energy's effects can also be detectable within galaxies, a much smaller scale than previously considered. By analyzing the rotation curves (velocity vs distance of stars, see in the figure above) on dwarf galaxies, they found that the upper limit of dark energy's influence is surprisingly close to known values—just two orders of magnitude higher.

This groundbreaking discovery implies that dark energy has a much more significant impact on galaxy dynamics than previously believed, potentially disrupting the balance between dark matter's gravitational pull and dark energy's push, leading to galactic instability. The research funded by Carl Wilhelm Fueck-Stiftung and Margarethe und Herbert Puschmann-Stiftungs opens new avenues for studying dark energy within galaxies, offering fresh insights into its relationship with dark matter. The results challenge previous assumptions, suggesting that dark energy has an impact on much smaller scales than considered before.

The research shows that in galaxies with large orbital periods, the impact of dark energy reduces the velocity in the outskirts. Therefore, the researchers claim that with future measurements focused on the outer regions of galaxies, it will be possible to detect dark energy on much smaller scales than we currently imagine. This could lead to a profound shift in our understanding of the universe’s fundamental forces.

Publication: David Benisty, David Vasak, Jürgen Struckmeier, Horst Stöcker, Bounding the Cosmological Constant using Galactic Rotation Curves from the SPARC Dataset, Phys.Rev.D 110 (2024) 6, 063028, https://doi.org/10.1103/PhysRevD.110.063028.

more information