An international team of researchers, led by the University of Vienna, has revealed that the Solar System passed through the complex Orion star-forming region, a structure linked to the so-called Radcliffe Wave, approximately 14 million years ago. This interstellar journey may have reduced the size of the heliosphere—the protective bubble surrounding our planetary system—allowing greater amounts of interstellar dust to enter Earth, which could have left traces in geological records and had implications for Earth’s climate. The findings, published in the journal Astronomy & Astrophysics, establish a fascinating interdisciplinary link between astrophysics, paleoclimatology, and geology.
The movement of the Solar System through the Milky Way takes it through different galactic environments, each with its own unique physical and chemical characteristics. It’s like a ship sailing through seas with changing conditions, explains Efrem Maconi, a PhD student at the University of Vienna and lead author of the study. On its journey, our Sun encountered a region with higher gas density when it passed through the Radcliffe Wave in the Orion constellation.
Thanks to data collected by the European Space Agency’s (ESA) Gaia mission and spectroscopic observations, the team was able to determine with precision that the Solar System’s passage through the Orion region occurred approximately 14 million years ago. This discovery expands our knowledge of the Radcliffe Wave, notes João Alves, professor of astrophysics at the University of Vienna and co-author of the study. This vast, wave-shaped galactic structure is composed of multiple interconnected star-forming regions, including the famous Orion complex, through which our planetary system made its interstellar journey.
During this passage, the Orion region was home to star clusters in the midst of formation, such as NGC 1977, NGC 1980, and NGC 1981. From Earth, this area is visible in the night sky during winter in the Northern Hemisphere and summer in the Southern Hemisphere. Just look for the Orion constellation and the Orion Nebula (Messier 42), as our Solar System comes from that direction, explains Alves.
One of the potential effects of this galactic encounter is the increase of interstellar dust in Earth’s atmosphere. This material may have introduced radioactive elements from supernova explosions, whose traces could be found in the planet’s geological records. Although current technology is not yet sensitive enough to detect these traces with certainty, future advancements may make their identification possible, says Alves.
According to the study, the Solar System’s passage through the Orion region occurred between approximately 18.2 and 11.5 million years ago, with the highest probability that it happened between 14.8 and 12.4 million years ago. Interestingly, this timeframe coincides with the Middle Miocene Climate Transition, a period marked by a shift from a warm and variable climate to a progressive cooling that led to the consolidation of the Antarctic ice sheet on a continental scale. Although the researchers suggest that interstellar dust may have influenced this climate change, they emphasize that further studies are needed to confirm a direct causal relationship.
Although the exact mechanisms behind the Middle Miocene Climate Transition are not yet fully understood, available reconstructions suggest that a sustained decrease in atmospheric carbon dioxide concentration was the primary cause of this cooling, explains Maconi. However, our study highlights that interstellar dust resulting from the passage through the Radcliffe Wave may have played an additional role in this process.
Nevertheless, the researchers stress that this geological event cannot be compared to contemporary climate change, as the Middle Miocene Transition took place over hundreds of thousands of years, whereas today’s global warming is occurring over a timescale of decades to centuries due to human activity.
This study adds a key piece to the puzzle of the Solar System’s recent history, placing it within the broader context of the Milky Way. We are inhabitants of the galaxy, and ESA’s Gaia mission has allowed us to trace our recent route through the interstellar sea, enabling astronomers, geologists, and paleoclimatologists to work together to better understand these phenomena, concludes Alves.
In future research, the team led by Alves plans to analyze in greater detail the galactic environment through which the Sun has traveled during its journey through the galaxy, in order to determine what other factors may have influenced our planet throughout its history.
SOURCES
E. Maconi, J. Alves, et al., The Solar System’s passage through the Radcliffe wave during the middle Miocene. Astronomy & Astrophysics, 2025; 694: A167 DOI: 10.1051/0004-6361/202452061
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