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Home » Milky Way Satellite Galaxies Mystery Solved After More Than 50 Years

Milky Way Satellite Galaxies Mystery Solved After More Than 50 Years

  • Space
milky way galaxy

Astronomers believe they have solved a long-standing mystery about the evolution of the Universe: the spatial distribution of weak satellite galaxies around the Milky Way. The unusual arrangement of these satellite galaxies, known as the plane of satellites, makes them seem to be on a vast, narrow, spinning plane.

The plane of satellites is a cosmic aberration that will disappear over time like star constellations, according to a recent study done in partnership with the Universities of Durham and Helsinki. The research was reported in Nature Astronomy.

As stated in the press release, these satellite galaxies have an unusual orientation as they appear to reside within a vast, thin rotating plane known as the Plane of the Satellites. For more than 50 years, astronomers have been baffled by this seemingly improbable arrangement, leading many to question the validity of the conventional cosmological model that aims to explain how the Universe came to look the way it does today.

Positions and orbits of the 11 classical satellite galaxies of the Milky Way, projected “face-on” (top) and “edge-on” (bottom), integrated for 1 billion years into the past and future.
Till Sawala / Sibelius collaboration 

Their solution overcomes the cosmological standard model’s difficulty with the plane of satellites. This theory describes how galaxies evolved gradually among clumps of cold dark matter, a mysterious component that accounts for around 27% of the Universe.

The satellites of the Milky Way appear to be organised in an implausibly thin plane piercing the galaxy, while also rotating in a coherent & long-lived disk. There is no known physical mechanism that may convert satellites into planes. Instead, satellite galaxies were projected to form a roughly circular shape as they tracked the dark matter.

“Satellites were mind-boggling”

Since the 1970s, when the plane of satellites was discovered, astronomers have made repeated fruitless attempts to uncover equivalent structures in accurate supercomputer models of the Universe’s evolution from the Big Bang to the present.

On the other hand, in this most recent study, astronomers benefited from fresh information from the European Space Agency’s GAIA space observatory. GAIA is building a six-dimensional map of the Milky Way and offers precise positions and velocities measurements for almost a billion stars in our galaxy.

“The strange alignment of the Milky Way’s satellite galaxies in the sky had perplexed astronomers for decades, to the point where it was deemed to pose a profound challenge to cosmological orthodoxy,” study co-author Professor Carlos Frenk, Ogden Professor of Fundamental Physics in Durham University’s Institute for Computational Cosmology, said.

“However, because to the incredible data from the GAIA satellite and the laws of Physics, we now know that the plane is simply a chance alignment, a matter of being in the right location at the right moment, just like the constellations of stars in the sky,” he added.

“The plane of satellites was simply mind-boggling,” stated study lead author Dr. Till Sawala of the University of Helsinki.

“It is probably unsurprising that a puzzle that has persisted for nearly fifty years needs a combination of ways to solve – and an international team to come together.”