The current climate change on Earth is caused by human activity, but the gravitational pull of other planets can also create long-term climate patterns by slightly altering the trajectory of our planet.
Recent research indicates that passing giant stars could also change the path of Earth – and these cosmic forces may limit researchers’ ability to connect past changes in Earth’s orbit with our planet’s climate.
A star in the constellation Lizard appears to be pulling a trail of stardust behind it. (Photo: NASA Goddard).
The paths of Earth around the Sun change over time. For instance, Earth’s orbital shape transitions from near-circular to elliptical approximately every 100,000 years due to the gravitational influence of Jupiter and Saturn. This Milankovitch cycle affects the amount of solar radiation our planet receives, partially altering the climate and periodically ushering us into ice ages.
Similar to weather forecasts, measurements become less accurate over longer time spans because the uncertainty regarding the paths of planets increases exponentially. Consequently, scientists previously believed they could only accurately predict Earth’s trajectory for about the last 70 million years.
In fact, in December 2023, researchers calculated that a star could be a billion years away. Now, if it were to nudge Earth off its orbit, it could potentially save it from being consumed by the expanding Sun.
This study inspired two members of the same research group to explore the impacts a passing star could have on Earth’s orbit in the past.
Nathan Kaib, a senior scientist at the Planetary Science Institute in Arizona, stated: “We just decided to see what would happen if we started simulating a series of stars passing through the Solar System.”
Kaib and co-author Sean Raymond, an astronomer at the University of Bordeaux in France, utilized computer models to create hundreds of backward predictions about the paths of planets in the solar system. This research was recently published in the Astrophysical Journal.
In some scenarios, the researchers allowed a star similar to the Sun to approach within 200,000 astronomical units (AU) from the Sun. They found that adding a star passing by reduced the forecast period from 77 million years down to just 62 million years.
The researchers also discovered that stars create a cosmic domino effect, pulling on massive gas planets and subsequently pushing Earth.
