As our solar system orbits the Milky Way, we encounter a variety of environments, including dense regions of interstellar media. These encounters can increase the flow of interstellar dust into the solar system and the Earth's atmosphere, exposing parts of the solar system to interstellar mediums. The discovery of new galactic structures, such as the Radcliffe waves over the 9,000 Wright years, raises the question of whether the Sun encountered any of them. New research shows that the solar system trajectories intersected with the waves of Radcliffe in the Orion star-forming region 15 to 12 million years ago (Miocene era). In particular, this period coincides with the mid-Miocene climate transition on Earth, providing an interdisciplinary connection with paleoclimatology.

When the solar system brings the Milky Way into orbit, we encounter a variety of galactic environments with different interstellar densities, including hot voids, fronts of supernova blasts, and cold gas clouds.

The passage of the sun through dense regions of interstellar media can affect the solar system in several ways.

For example, pressure enhancement compresses the heliosphere and exposes parts of the solar system to cold, dense interstellar media.

Furthermore, the amount of interstellar dust mounted on the Earth's atmosphere can increase, potentially enhancing the delivery of radioactive isotopes such as iron-60 through dust grains.

Radcliffe's waves are narrow sinusoidal gas structures and consist of many known star-forming cloud complexes, including CMA, Orion, Taurus, Perseus, Cephaus, North American Nebula, and Cygnus.

With an estimated mass of 3 million people, this gas structure appears to vibrate consistently like a moving wave and is thought to be part of the Milky Way spiral structure.

Dr. Efrem Macconi, a doctoral student at the University of Vienna, said:

“Our Sun encountered a higher gas density region as it passed through the waves of Radcliffe in the Orion constellation.”

Using data from ESA's Gaia mission and spectroscopic observations, Dr. Maconi and his colleagues identified the passage of the solar system through the Radcliffe Wave in the Orion area.

“The findings are based on previous works identifying Radcliffe's waves,” said Professor Joanne Albes of the University of Vienna.

“We passed the Orion area as well as famous star clusters like NGC 1977, NGC 1980 and NGC 1981.”

“The area is easily visible in the winter sky in the Northern Hemisphere and in the summer in the Southern Hemisphere.”

“Look for Orion Constellation and Orion Nebula (Messier 42) – our solar system has come from that direction!”

“The increased dust from this galaxy encounter may have had some effects.”

“It could potentially leave traces of radioactive elements from supernovas in the geological record that permeate the Earth's atmosphere.”

“Current technologies may not be sensitive enough to detect these traces, but future detectors may make it possible.”

This study shows that the solar system passing through the Orion region occurred around 18.2 to 11.5 million years ago, with the most likely time between 148 and 12.4 million years ago.

This time frame is in good agreement with the mid-Miocene climate transition, and is a major shift from warm variable climate to cool climates, leading to the establishment of a continental-scale prototype Antarctic ice sheet composition.

This study raises the possibility of a link between past crossings of the solar system through galaxy neighbours and Earth's climate through interstellar dust, but the authors need further investigation of the causal relationship. It emphasizes that there is.

“The basic processes responsible for the mid-Miocene climate transition have not been fully identified, but available reconstructions are most likely to be long-term reductions in atmospheric greenhouse gas carbon dioxide concentrations. It suggests that it is a high explanation.

“However, our research highlights that interstellar dust associated with the crossing of Radcliffe's waves has affected the Earth's climate and may have played a potential role during this climate change. Masu.”

“To change the Earth's climate, the amount of extraterrestrial dust on Earth needs to be much larger than what previous data suggests.”

“Future research explores the importance of this contribution. This past climate change and current climate change is comparable as this past climate change is unfolding over a timescale of hundreds of thousands of years. It is important to note that we do not do that.”

“In contrast, the evolution of global warming today has been happening at an unprecedented rate for decades to centuries due to human activity.”

study Published in the journal Astronomy and Astrophysics.

____

E. Machoni et al. 2025. Passing through the solar system through the waves of Radcliffe in the mid-Miocene. A&A 694, A167; doi: 10.1051/0004-6361/202452061