Dwarf galaxies align: the mystery finally solved? 🌀

Dwarf galaxies often appear to align mysteriously around their host galaxies. A new study proposes an unprecedented explanation.

Galaxies like the Milky Way are surrounded by dozens of dwarf galaxies, whose positions are not random. These satellite galaxies often form coherent planes, a phenomenon observed since the 1970s but lacking a satisfactory explanation until now.


Traditional computer simulations struggled to reproduce these alignments. A team of researchers thus developed more sophisticated models, precisely integrating dark matter and gas flows over billions of years. Their results finally shed light on this mystery.

Cosmic filaments, true matter highways, play a key role. When they interact, they can lock dwarf galaxies into a common plane. Two main mechanisms have been identified: the 'zipper' and the 'twister,' which respectively stabilize or modify the plane's orientation.

This discovery resolves a major contradiction between theory and observations. Researchers estimate that 50 to 70% of galaxies similar to the Milky Way and Andromeda should exhibit these satellite galaxy alignments, perfectly matching current data.

The implications go beyond simply understanding dwarf galaxies. This work also provides valuable clues about dark matter behavior, this invisible component that structures the Universe on a large scale.

The James Webb Telescope could soon bring new confirmations. Its observations of primordial galaxies will test whether these mechanisms were already at work in the young Universe, opening a new window on cosmic history.

How does dark matter influence galaxy formation?

Dark matter constitutes about 85% of the Universe's total matter. Though invisible, it acts as a gravitational skeleton guiding the formation of cosmic structures.

Simulations show that dark matter first forms a 'halo' around future galaxies. This halo gradually attracts ordinary gas, which eventually condenses into visible stars and galaxies.

The distribution of dark matter thus directly determines the architecture of galaxies and their satellites. The new models better integrate this influence, finally explaining the observed alignments.

These advances confirm dark matter's central role in cosmic evolution while opening avenues to better understand its fundamental properties.

What do dwarf galaxies teach us about the primordial Universe?

Dwarf galaxies are considered cosmic fossils, preserving key information about the Universe's earliest phases. Studying them allows us to travel back through cosmic time.

Unlike large galaxies, many dwarfs have experienced few major mergers. Their ancient stars and low metallicity make them privileged witnesses of initial conditions.

Dwarf galaxy alignments also reveal how matter assembled in the young Universe. Primordial filaments, now indirectly visible through these structures, trace the original cosmic scaffolding.