Dark matter ‘rogue waves’ could disrupt stars’ orbits

A fascinating new study suggests that massive, invisible concentrations of dark matter could exert an influence on binary stars. If so, these subtle perturbations would offer a unique opportunity to unravel the mystery surrounding its nature.

The Dark Matter Enigma

For decades, astronomers have peered into the far reaches of the universe and collected a wealth of compelling evidence supporting the existence of dark matter. This enigmatic substance, elusive to traditional means of detection, remains invisible to our most sophisticated instruments. Yet despite its stealthiness, it plays a fundamental role in cosmic dynamics, contributing significantly to the total mass of galaxies and the structure of the observable Universe. Initially, scientists hypothesized that dark matter might consist of weakly interacting massive particles known as WIMPs. However, despite numerous attempts, experiments aimed at detecting these particles have not yielded conclusive results. Faced with this challenge, researchers have broadened their perspective and considered an intriguing alternative model. In this new theoretical framework, the particle that constitutes dark matter would be incredibly lightsurpassing even the lightness of the neutrinoa particle already known for its almost elusive mass. This bold idea has opened new avenues of research and prompted scientists to explore new avenues to understand the nature of this enigmatic substance. One of them suggests that vast aggregates of light dark matter may play a crucial role in cosmic dynamics, affecting the structure and evolution of galaxies and star systems.

“Rogue waves” of dark matter

As said above, according to this theoretical model, the dark matter particle would be incredibly light, far exceeding the mass of the electron. by a factor of more than a billion billion. This extreme lightness would give dark matter special properties, allowing it to act more like a wave on a scale comparable to or larger than that of the Solar System. In response to this innovative prospect, a team of Chinese astronomers set out to explore this model and find ways to observe this ultralight dark matter. According to this theory, ultralight dark matter would not move through the cosmos as individual particles, but rather as an invisible ocean enveloping each galaxy. And just as Earth’s oceans can generate waves, this pool of ultralight dark matter could then also undergo oscillations, some of which group together into coherent structures called solitons.
Dark matter (shown in blue in this composite satellite image) dominates up to 85% of the mass of most galaxies. Credits: NASA, ESA, CFHT, CXO, MJ Jee, A. Mahdavi

Target binary couples

These solitons would be completely invisible, but their enormous size could subtly influence the gravitational environment around them. Although their influence is generally minimal on most objects in the galaxy, binary star pairs could nevertheless be sensitive to these solitons. As a reminder, these objects consist of two stars that orbit around their common center of mass under the influence of their mutual gravity. Compared to other more massive systems, such as star clusters or galaxies, the gravitational binding between the two stars in a binary pair is relatively weak. This means that the stars involved are less strongly bound to each other by gravity. As a result, external perturbations, such as those caused by massive objects or astrophysical phenomena, can have a more significant impact on these objects. For example, if an ultralight dark matter soliton passes through the gravitational field of a pair of binary stars, it could induce subtle changes in their orbits by exerting a slight gravitational force on them. The researchers now plan to identify all pairs of large binary stars in the Gaia catalog, comprising billions of stars closest to the Sun, for future observations. Perturbations in the orbits of these binary stars could then provide a valuable clue about the nature and distribution of this enigmatic dark matter that is potentially more revealing than experiments conducted in terrestrial laboratories. The researchers have published their work on the preprint server arXiv in April. The study has not yet been peer-reviewed.