[video] A passing star altered Earth’s orbit 2.8 million years ago

Researchers say Sun’s encounter with other stars is a common phenomenon – this happens every 1 million years.

Our planet’s orbit around the Sun has not been exactly the same since the inception of the Solar System – and isn’t actually stable after all – but 2.8 million years ago a passing star surely perturbated Earth’s orbital dynamics.

A new study published in the Astrophysical Journal Letters suggests that the stellar encounter also created ancient climate anomalies, which were investigated by Planetary Science Institute researchers when they sensed a possible connection with the visitor, called HD-7977. 

This star passed by the Sun at a distance between 4,000 and 32,000 astronomic units (AU – the distance from Earth to Sun, or 93 million miles / 150 million kilometers).

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Lead author Nathan Kaib, a senior scientist at the Planetary Science Institute, emphasized in a press release the relevance of understanding Earth's orbital characteristics during past climate shifts, citing the correlation between orbital eccentricity variations and climate fluctuations evident in the geological record. 

"If we want to best search for the causes of ancient climate anomalies, it is important to have an idea of what Earth's orbit looked like during those episodes," he noted.

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According to Kaib’s team, the HD-7977 – Sun encounter could have exerted enough gravitational force to disrupt Earth's orbit. Orbital simulations conducted by researchers suggest that interactions with massive outer planets like Jupiter and Saturn could further amplify these effects, indicating a mechanism through which distant stellar encounters influence our planet.

Stellar flybys introduce uncertainties into projections of Earth's orbital evolution, complicating interpretations of geological data. Kaib and his team argue that these uncertainties could significantly impact our understanding of past climate events, such as the Paleocene-Eocene Thermal Maximum, where Earth experienced substantial warming.

They caution that detailed predictions about Earth's orbital history during such periods become highly uncertain in light of potential influences from passing stars, suggesting a broader spectrum of orbital behaviors than previously assumed.

The impact of the 2.8-million-year-old flyby on our planet’s orbit will become more visible over time, say a few million years ahead, as suggested in the simulation below. 

Stellar encounters aren't uncommon, as a matter of fact: a star passes within 50,000 AU of the Sun every 1 million years on average, and every 10 million years for within 10,000 AU.

It’s a long distance, don’t worry. Neptune, the most distant planet from the Sun in the Solar System, is located approximately 30 AU away from it.

Check the video for the simulation. 

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