Passing Stars Altered Earth's Orbit Millions Of Years Ago, Finds Study

Stars that pass by our solar system sometimes have profound impact on the planets. According to a new research, such an event may have changed Earth's orbit enough to wreak havoc on the climate. The event occurred millions of years ago and Earth's temperature rose by up to 8 degrees Celsius. Titled 'Passing Stars as an Important Driver of Paleoclimate and the solar system's Orbital Evolution', the research has been published in The Astrophysical Journal Letters. The lead researchers are Nathan A Kaib and Sean Raymond.

"Perturbations - a minor deviation in the course of a celestial body, caused by the gravitational attraction of a neighbouring body - from passing stars alter the long-term orbital evolution of the sun's planets, including Earth," said Mr Kaib, Senior Scientist at the Planetary Science Institute.

"One reason this is important is because the geologic record shows that changes in the Earth's orbital eccentricity accompany fluctuations in the Earth's climate. 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 added.

To piece together what happened in Earth's 4.5-billion-year lifespan requires extensive scientific research. The research team ran simulations to predict past orbital evolution of our planet.

Then it chose a single known event that occurred 2.8 million years ago when a Sun-like star called HD 7977 passed the Solar System, potentially so closely that it flew inside the Oort Cloud.

It may have flown past at a distance of some 31,000 astronomical units (1 astronomical unit is the distance between Earth and the Sun), and too far to have had much effect. But it may have zoomed in as close as 4,000 astronomical units.

Such close encounter had some sort of gravitational influence on the movement of the planets in relation to the Sun.

"It has already been proposed that Earth's orbital eccentricity was notably high during this event, but our results show that passing stars make detailed predictions of Earth's past orbital evolution at this time highly uncertain, and a broader spectrum of orbital behaviour is possible than previously thought," said Mr Kaib.