All of them revolve around the Sun due to its strong gravitational force. But is this the maximum number of planets that can orbit the Sun, or is there room for more?
Compared to other known planetary systems, the Solar System contains an unusually high number of planets. According to The Extrasolar Planets Encyclopaedia, a total of 812 planetary systems have been discovered with at least three confirmed planets, and only one other known system, Kepler-90, has as many planets as the Solar System.
The Solar System comprises the Sun, eight planets, at least 138 moons, comets, asteroids, and various types of space rocks. Image: NASA.
There could be many planetary systems out there with smaller planets that we haven’t detected, so it’s uncertain whether the Solar System is truly the most populous planetary system in the universe. However, the eight planets are close to the upper limit of the size range that a planetary system can naturally develop.
To calculate the absolute maximum capacity of planets orbiting the Sun, one needs to delve into theory, disregarding certain natural factors that could limit the number of planets that can form. One of the best ways to do that is to design an entirely new Solar System from scratch.
After considering the important variables needed to design a planet-rich Solar System, researchers have determined the figures and assessed how many planets the Solar System can accommodate within it. It’s important to note that while these calculations are based on the theory used by astronomers to generate valid simulations, these models are not definitive.
To maximize the number of planets, the system is designed to expand to 1,000 astronomical units (AU) from the Sun (1 AU is the average distance from the Sun to Earth’s orbit, approximately 150 million kilometers). Currently, the outer edge of the Solar System, known as the heliopause, is about 100 AU from the Sun, according to the European Space Agency, but the gravitational influence of the Sun can extend much farther.
If all planets were Earth-sized, the Solar System would have 57 orbits, each containing 42 planets, resulting in a total of 2,394 planets. If the planets were only one-tenth the size of Earth, there would be 121 orbits, each containing 89 planets, totaling 10,769 planets. And if the planets were the size of the Moon, there could be 341 orbits, each containing 193 planets, resulting in a total of 65,813 planets.
Clearly, these numbers are astronomically large, and the ability to design such complex systems is far beyond the reach of humanity. However, this fascinating thought experiment highlights that there is much more space for planets within the Solar System than just the limited eight planets we see today. Nonetheless, it is highly unlikely that any additional planets have formed naturally.