The journey of the Solar System around the center of the Milky Way impacted the climate during the Middle Miocene period.

An international research team led by Efrem Maconi from the University of Vienna (Austria) has reached a remarkable conclusion: between approximately 18 and 11.5 million years ago (most likely around 14 million years ago), the Sun and all its planets crossed the Radcliffe wave in the vicinity of the Orion constellation. The results of this new scientific study have been published in the journal Astronomy & Astrophysics.

Over hundreds of millions of years, our solar system orbits around the center of the Milky Way, allowing it to traverse various regions of the Galaxy. Similar to a ship caught in a storm, the Solar System entered a dense area of Orion and encountered a massive structure of gas and dust—a part of the Radcliffe wave.

To trace the orbit of the Solar System, scientists analyzed precise measurements of the positions and movements of stars, obtained through the Gaia space observatory and supporting spectroscopic data. This enabled them to "rewind" the history of the Sun and planets' movements and discover that 14 million years ago, our solar system entered the area where the Orion Nebula is located today.

This densely packed region of interstellar medium likely affected the size of the heliosphere and increased the influx of dust. This additional influx of cosmic dust particles may have reached Earth and left, for instance, traces of radioactive isotopes in sedimentary rocks. Although scientists cannot directly "see" such traces today, advancements in technology may change that in the future.

At the same time, a middle Miocene climatic transition was occurring on Earth, meaning the climate was shifting from warmer to cooler as the Antarctic ice cover expanded. The primary explanation for this is the prolonged decrease in CO₂ concentration and changes in geological conditions; however, the authors of the new scientific paper did not rule out that the influx of dust from dense interstellar regions may have contributed to the cooling.

The fact is that even minor changes in the reflectivity of sunlight by Earth’s atmosphere significantly alter its climate. Such particles would have increased Earth's albedo, promoting global cooling.

Thus, scientists have learned about the regions of the Milky Way that our Solar System has traversed, linking its journey to geological records. Further research will determine how significant this event was for Earth’s history. Astronomers noted that they will continue to study the interstellar environment through which our star has traveled at various points in its galactic trajectory.