Diagrams and animations showing planetary orbits are a bit of a lie, or more accurately, they simplify the orbits of the planets so that teachers don’t have to explain the center of gravity to children who don’t yet understand that Earth is not the only planet.
The way planetary orbits are typically taught is something like the video below.
But that’s a simplified version: even though the Sun is the largest object in the Solar System, with a mass about 1,048 times that of Jupiter, gravity goes both ways: just as the Earth exerts a gravitational force on you, so too does it on the (much smaller) Earth.
“Kepler’s third law describes the relationship between the masses of two bodies rotating relative to one another and the determination of their orbital parameters.” NASA explains.
“Consider a small star orbiting a more massive star. Both stars actually orbit around a common center of mass, or barycenter. This is true regardless of the size or mass of each object involved. Measuring the motion around the barycenter of a star with a massive planet is one method that has been used to discover planetary systems associated with distant stars.”
In simple terms, the planets revolve around the Sun. However, the center of gravity of the solar system objects is usually near Because it is the most massive, it is thought to be inside the Sun, but due to the orbits of Jupiter and Saturn and the influence of gas giants, it is unlikely to actually be inside the Sun. Its orbit looks a bit like this video from planetary astronomer and science communicator: James O’Donoghue.
As a result, the Earth’s center of gravity is outside the Sun, so the Earth is not currently orbiting a point inside the Sun. We are orbiting a point in space, not the Sun.
“Generally speaking, the planets orbit the sun,” O’Donoghue says. Explain with X (Twitter) “But *technically*, the planets don’t orbit the Sun on their own, because the gravitational influence of (mainly) Jupiter forces them to orbit new points in space.”
“Of course the planets go around the sun, but we’re just too hung up on the situation,” he says. Added“It’s natural to think of us as orbiting the center of the sun, but that’s extremely rare — it’s extremely rare for the center of mass of the solar system to be aligned with the center of the sun.”
The same is true for smaller objects such as planets and their moons. The Earth and Moon are 5,000 kilometers (3,100 miles) from the center of the Earth, but this distance changes as the Moon moves further and further away from the Earth.
While these facts probably have little impact on your life (assuming you’re not an astrophysicist), they’re still interesting and serve as a reminder that almost everything is a bit more complicated than we were taught in school.