New research suggests that stars passing close to our solar system millions of years ago may have caused significant changes to Earth’s climate. According to a study published in The Astrophysical Journal Letters, when a star called HD 7977 came within 4,000 astronomical units of our solar system about 2.8 million years ago, it likely raised Earth’s temperature by 8 degrees Celsius.
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An astronomical unit is the average distance between the Earth and Sun. 4,000 astronomical units is still very far in cosmic terms, but close enough for HD 7977’s gravity to potentially disturb the orbits of planets in our solar system. Lead author Sean Raymond, an astronomer, explained that the resulting changes to Earth’s orbit around the sun would have shaken up climate patterns.
To reconstruct what happened, the researchers ran computer simulations of past orbital movements in our solar system going back billions of years. Their models suggest the close flyby of HD 7977 shifted the path of Earth’s orbit enough to alter climate temporarily before settling back to original conditions.
While the sun is the main driver of Earth’s climate, gravitational tugs from passing stars can lead to long-term wobbles and tilt changes in planetary orbits. Astronomer Nathan Kaib, a co-author, said this helps explain mysterious climate shifts evident in the geological record that have defied full explanation until now.
The study demonstrates how the motions of distant stars can have tangible impacts on planets many light years away. Improved mapping of stars near our interstellar neighborhood will shed light on the role they may have played in Earth’s past climates. It also underscores the connectedness of forces across the cosmos.
