Scientists have discovered that another planet could enter the Solar System. Here's how it might happen.

So far, the only interstellar objects that have visited the Solar System are Oumuamua and comet 2I/Borisov. However, similar objects may visit the Solar System in the future, including wandering planets in space. Scientists believe that the Sun could gravitationally capture any rogue planet that becomes part of the Solar System. What will happen to other planets is still uncertain, as it depends on the mass of the object and its eventual orbit. It is possible that a new planet could create orbital chaos, permanently altering life on Earth. The authors of a paper published in the journal Celestial Mechanics and Dynamical Astronomy described how the Solar System might acquire a new planet, reports ScienceAlert.

Phase space is a mathematical representation of the state of a dynamic system, such as the Solar System. It resembles a multidimensional space that encompasses all possible orbital configurations around the Sun. The phase space of the Solar System contains capture points where a wandering planet may become gravitationally bound to the Sun.

The phase space of the Solar System includes two types of capture points: weak and permanent.

• Weak capture points are regions in space where an object can be temporarily captured on a somewhat unstable orbit. These points are located where the outer edges of the gravitational boundaries of objects converge.
• Permanent capture points are areas in space where an object can be permanently captured on a stable orbit. In planetary systems, these permanent capture points represent stable orbital configurations that are maintained over extremely long periods.

Slight changes in the coordinates of phase space may allow objects to transition between states of permanent capture and weak capture. Similarly, minor differences in wandering planets may lead them to these points.

According to scientists, permanent capture of an object from interstellar space by the Sun occurs when it can never return to interstellar space and remains within the Solar System, moving without colliding with the Sun. However, sometimes an interstellar object can be in a state of weak permanent capture. An object in a state of permanent weak capture will never escape but will also never achieve a permanent, stable orbit.

Many planets that form around other stars, due to gravitational interactions with other planets, can be ejected from their native systems and become wandering worlds. Scientists have created a cross-section of capture for the phase space of the Solar System and then calculated how many rogue planets are in the vicinity of the Solar System.

Within approximately 20 light-years from us, there are 131 stars. Some of these have planets, while others have yet to be discovered. Stars, along with their planets, periodically come close to the Sun, and there is a possibility that some planets may leave their home star system.

Scientists have identified holes in the phase space of the Solar System that could allow some of these wandering planets to achieve permanent weak capture.

These holes are located in the Hill sphere of the Sun, where the Sun's gravity is the dominant gravitational force for capturing any satellites. These holes are situated nearly 4 light-years from the Sun in the direction of the galactic center.

According to scientists, permanent weak capture of planets is possible through these holes. A new planet or planets will never collide with the Sun but could disrupt the orbits of existing planets.