Why and what does that mean?

We all know that the Earth revolves around the Sun, but in reality this statement is true (at least these months). Technically forged. In fact, Earth – like all other planets, asteroids and comets in the solar system – technically orbits the Sun. center of gravity (or Center of mass) of the solar system itself, which does not exactly coincide with the center of the sun. Our star contains approximately the center of the Sun. 99.9% of the total mass Solar System (about 2000 billion billion kilograms), but depending on the arrangement of the different planets, their mass contribution, although low, can mean that at certain periods the center of gravity of the Solar System is located outside the Solar System. The sun itself (although it is still close). Well, this is one of those times: the Earth — and technically also the rest of the solar system, including the Sun itself — revolves around it. About the common center of gravity For the entire system, which is offline point outside the sun.

What is the center of gravity and where is the center of gravity of the solar system located?

The center of gravity is Geometric point Who acts as if The entire body mass was concentrated there.. Its location depends on Average of the mass distribution Which make up the body itself, so it tends to move towards where the matter is more “concentrated”. The location of the center of gravity changes with time, as do the positions of the planets along their orbits, which are determined by Kepler's laws. Most of the contribution to the center of mass, with the exception of the Sun, comes from the more massive planets, namely Jupiter, Saturn, Uranus, and Neptune. Every one of these planets Tends to “drag” The center of mass towards itself, thus creating Sometimes constructive contributions (When the planets are “all on the same side” to the Sun) And sometimes destructive (When it is distributed in all directions around our star).

When contributions are yes Constructive additionThe end result is that the center of mass of the solar system is located Out of the sunUp to approx. 700,000 km From its surface. During this period, we find ourselves in a constructive situation in which the center of gravity is outside the sun, while the contributions of the sun and planets are in place. They add in destructive waysThe center of mass tends to lie inside the Sun, up to about 350,000 km from its center (the Sun, for comparison, has a radius of about 700,000 km). This will happen in 2029-2030.

In the animation below you can see the location of the center of gravity of the solar system from 2020 to the next century.

The importance of the center of gravity in astronomy

The same concept applies to any system of orbiting bodies: technically, two (or more) bodies. They revolve around the common center of gravity. This also happens with the Earth and the Moon. These two celestial bodies do not revolve around each other, but rather revolve around each other Common center of gravity Which is located approx 4671 km from the center of the EarthTherefore, directly below the surface of the Earth.

Objects rotating around the center of gravity can be used among other things Discovery of exoplanets Outside the solar system. In fact, measure Radial velocity The star and how it differs because of it Oscillation around the center of gravity For a star system, the amplitude of oscillation gives us information about… Collective contribution Other objects that are part of the system, leading us to discover whether exoplanets exist around a particular star.