As children we were taught that Jupiter revolved around the Sun. Technically we were deceived

If you are over 30 years old, you probably learned in school that there are nine planets that revolve around the Sun. Then you found out that there were eight, because suddenly Pluto lost its planet category and became a dwarf planet. As if all that were not enough, now I am here to tell you that Jupiter does not revolve around the Sun. Sometimes not even the Earth does. We have been deceived or, rather, we have been told everything quite simplified.

It is not the center, but the barycenter. There is a lot of talk about the gravitational attraction that large objects exert on smaller ones. The Sun on the Earth, the Earth on the Moon, the Earth on the people who walk on it… However, smaller objects also exert a certain gravitational pull on larger ones. It is tiny, sometimes imperceptible, but it is there. Therefore, although it is the Sun that dominates the planets of the Solar Systemeach one of them also pulls a little bit of it. This means that the center around which they all rotate is not in the center of the Sun, but at a point slightly separated from it, known as the barycenter.

To understand it better. All objects have a center of mass. Broadly speaking, it is the point where we assume that all its mass is concentrated. It does not mean that all the mass is there, but for practical purposes, when doing calculations, it is considered that that is where it is concentrated. Because of how external forces interact with the object, it is right at the center of mass where it is best kept in balance.

For example, with an elongated object of homogeneous mass, such as a ruler, the center of mass will be its actual center. If we try to hold the ruler on a finger, the easiest thing to do is to place the finger right under its center. There it stays better in balance. On the other hand, in a hammer, where the heaviest thing is its end, its center of mass is there. In the case of the Solar System, the barycenter is the point where the mass of the system is concentrated. Logically, it is very close to the Sun, since 99.86% of the mass of the system corresponds only to the king star. However, there is influence from other masses, so it is a little far from the solar center.

The case of Jupiter. If the Sun is 99.86% of the masses of the Solar System, Jupiter accounts for 70% of the remaining mass. Therefore, individually it is the one that deviates the center of gravity the most. This means that the barycenter around which both Jupiter and the Sun itself move is outside the solar surface. Jupiter does not revolve around the Sun, but around a point that does not even cross the sun.

The case of the Earth and the Moon. In the case of the Earth and the Moon there is also a barycenter. The Earth is much larger than the Moon, but the Moon also has mass and exerts some power over it. For this reason, the barycenter is not right at the center of the Earth, but 5,000 kilometers from it. It is still within our planet, but not as centered as we usually think. Jupiter and the Sun are a more extreme case, which is why the center of gravity is completely outside the Sun.

The Earth does revolve around the Sun…sometimes. The Earth is much smaller than the Sun. If they were alone in the Solar System, the center of gravity would be practically in the center of the Sun. But of course, they are not alone. All planets act on the point where that center of mass is located. And the thing is, it’s a center of mass that moves as these planets move. Something similar happens to what happens when all the sailors on a ship move around the deck. The ship’s center of mass can change.

In the case of the Solar Systemthe most influential sailors are the gas giants. That is, Jupiter, Saturn, Uranus and Neptune. When these align, they pull the center of gravity outward and the Earth does not rotate around the Sun. In short, no, the planets do not rotate exactly around the Sun. But we are not going to get fancy explaining it at school either. Don’t feel like you’ve been fooled, they’ve just simplified it for you.

Image | NASA | Martin Jediny (Wikimedia Commons)

In Xataka | A planet has just disappeared: NASA’s Hubble telescope has captured a violent cosmic event that changes everything