The Sun's orbit around the Milky Way subjects it to varying galactic environments. "Think of it as a ship sailing through changing ocean conditions," explains Efrem Maconi, lead author and doctoral researcher at the University of Vienna. "As our Sun moved through the Radcliffe Wave in the Orion constellation, it encountered a region of increased gas density."

Utilizing data from the European Space Agency's (ESA) Gaia mission alongside spectroscopic observations, the researchers pinpointed the Solar System's passage through the Radcliffe Wave in the Orion region. "This study expands upon our previous research on the Radcliffe Wave," notes Joao Alves, professor of astrophysics at the University of Vienna and a co-author of the study. The Radcliffe Wave is a vast, thin structure linking multiple star-forming regions, including the well-known Orion complex, which our Sun traversed during the timeframe identified in this research.

"Our journey through the Orion region coincided with the formation of well-known star clusters like NGC 1977, NGC 1980, and NGC 1981," adds Alves. "This region is prominently visible in the Northern Hemisphere during winter and in the Southern Hemisphere during summer. By looking toward the Orion constellation and the Orion Nebula (Messier 42), one can trace the direction from which our Solar System arrived."

This interstellar encounter likely introduced increased dust into Earth's atmosphere, which could have deposited radioactive elements from past supernovae into geological records. "Current technology may not yet be sensitive enough to detect these traces, but advancements in future detectors might make it possible," suggests Alves.

The study estimates that the Solar System's passage through the Orion region occurred between 18.2 and 11.5 million years ago, with the most probable window being 14.8 to 12.4 million years ago. This period aligns closely with the Middle Miocene Climate Transition, a significant shift from a warmer, fluctuating climate to a cooler one, eventually leading to the formation of a large-scale Antarctic ice sheet. While the findings hint at a possible connection between the Solar System's interstellar journey and Earth's climatic changes through interstellar dust, the authors stress that further research is necessary to establish a causal relationship.

Not Comparable to Human-Induced Climate Change

"Our research suggests that interstellar dust from the Solar System's passage through the Radcliffe Wave may have played a role in this climate shift. However, for extraterrestrial dust to have significantly altered Earth's climate, the quantity would need to be much greater than current data suggests. Future studies will examine this possibility more closely. It is essential to recognize that this historical climate shift unfolded over hundreds of thousands of years, whereas current global warming, driven by human activity, is progressing at an unprecedented pace over mere decades to centuries."

This research provides a new perspective on the recent history of the Solar System, contextualizing its motion within the Milky Way. "We are residents of the Milky Way," says Alves.

"The ESA's Gaia mission has given us the ability to track our Solar System's path through the Galaxy, allowing astronomers, geologists, and paleoclimatologists to collaborate. It is an exciting time for interstellar exploration." Looking ahead, Alves and his team plan to investigate in greater detail the Galactic environment the Sun has encountered on its journey through the Milky Way.

Research Report:The Solar System's Passage through the Radcliffe Wave during the Middle Miocene.

Related Links
University of Vienna
Stellar Chemistry, The Universe And All Within It