When ‘Oumuamua crossed our solar system in 2017, it became the first interstellar object (ISO) to do so. Later in 2019, Comet 2l/Borysov did the same. These are the only two ISOs confirmed to have visited our solar system. Many other ISOs have likely visited our solar system throughout its long history, and many more will do so in the future. Clearly, there are more objects of this type, and the future Vera Rubin observatory is expected to reveal many more. Just as some planets capture moons, it is possible for the Sun to capture an ISO or stray planet.

It all depends on the phase space.

What would happen if our mature and dormant solar system suddenly gained another member? This will depend on the mass of the object and the final orbit it ends up in. This is an interesting thought experiment; Although Borisov and ‘Oumuamua are smaller objects, a larger rogue planet joining our solar system could create chaos in orbit. This could potentially change the course of life on Earth, although it is unlikely.

How likely is this scenario? New research note Celestial Mechanics and Dynamic Astronomy explains how our solar system is able to capture ISO. It’s called “The Continuing Magic of the Solar System” and its authors are Edward Belbruno of Yeshiva University’s Department of Mathematical Sciences and James Green, a former NASA employee who now works at Space Science Endeavors.

Phase space is a mathematical representation that describes the state of a dynamic system, such as our solar system. Coordinates representing both position and momentum in phase space are used. It is like a multidimensional space containing all possible orbital configurations around the Sun. Phase space captures the state of a dynamic system by tracking its position and momentum properties. There are capture points in the phase space of our solar system where the ISO can gravitationally attach to the Sun.

The phase space is complex and based on Hamiltonian mechanics. Things like orbital eccentricity, semi-major axis, and orbital inclination all affect this. Phase space is best understood as a multidimensional landscape. The phase space of our solar system contains two types of capture points: weak and persistent. Weak capture points are areas in space where an object can be temporarily placed in a metastable orbit. These points are often where the outer edges of objects’ gravitational boundaries meet. They are more like gravitational tremors than orbital perturbations.

Persistent capture points are areas in space where an object can be permanently captured in a stable orbit. An object’s angular momentum and energy are the precise configuration that allows it to maintain its orbit. In planetary systems, these permanent capture points are stable orbital configurations that persist for extremely long periods of time.

The phase space of our solar system is extremely complex and contains many moving objects and their changing coordinates. Small changes in coordinates in phase space can allow objects to switch between steady trapping states and weak trapping states. Likewise, subtle differences in ISO or stray planets can lead them to these points.

In their research notes, the authors describe persistent ISO trapping as follows: “Persistent capture of P, S, a small body from interstellar space around the Sun, occurs when P is never able to escape back into interstellar space and becomes trapped within the Solar System.” It will move without colliding with the Sun for all future time.”

Purists will note that nothing can be the same in the future, but the point still stands. Other researchers have explored this scenario in depth, but this study goes further. “In addition to being constantly excitable, P also has weak excitability,” they write. It revolves around the notoriously difficult three-body problem. Additionally, unlike previous studies that used Jupiter as the third body, this study uses the tidal force of the galaxy as the third body along with P and S.

“This tidal forcing has a significant impact on the structure of the phase space for the speed ranges and distances from the Sun that we consider,” they explain in their paper.

The article focuses on the theoretical nature of phase space and ISO trapping. He studies “the dynamical and topological properties of a special type of persistent entanglement, called persistent weak entanglement, that occurs over infinite time.”

An object with consistently weak capture can never escape, but it can never achieve a stable, stable orbit. It approaches the capture cluster asymptotically without colliding with the star. There is not much debate that rogue planets are likely to exist in large numbers. Stars form in groups and then disperse over a larger area. Since stars contain planets, some of these planets will be dispersed by gravitational interaction before the emerging stars separate slightly from each other.

“The ultimate architecture of any solar system will be shaped by interplanetary scattering, in addition to stellar explosions of neighboring star systems, as close collisions can eject planets and small bodies from the system, creating so-called rogue planets,” the authors explain.

“Taken together, early planet scattering, stellar collisions, and planet ejection in the later evolution of the multi-planet solar system should be commonplace and support evidence of large numbers of rogue planets floating freely in interstellar space, possibly exceeding the number of stars,” the authors write, noting that this claim is controversial. .

So what does all this mean?

The researchers developed a capture slice of the solar system’s phase space and then calculated how many rogue planets there are near our solar system. There are 131 stars and brown dwarfs in our solar neighborhood, which extends to a radius of six parsecs around the Sun. Astronomers know that at least a few of these contain planets, and all of them may have planets we haven’t discovered yet.

Every million years, about two stars approach our neighbor Earth within a few light-years. “But six stars are expected to fly close together in the next 50,000 years,” the authors write. Since the outer boundary of the Oort Cloud is about 1.5 light-years away, some of these stellar collisions can easily dislodge objects from the cloud and send them toward the inner Solar System. This has happened many times, as the cloud is likely the source of long-period comets.

Researchers have discovered holes in the solar system’s phase space that could allow some of these objects (ISOs, or rogue planets) to achieve persistent weak capture.

These are holes in the Sun’s Hill sphere, the region where the Sun’s gravity is the dominant gravitational force for capturing moons. These holes are located 3.81 light-years away from the Sun, towards or directly opposite the center of the Galaxy.

“Through these holes, a persistent weak capture of interstellar objects into the Solar System is possible,” the authors claim. “They would move chaotically around the Sun towards a continuous capture in the Hill sphere, which would take an arbitrarily long time over an infinite number of cycles.”

These objects never hit the Sun and can be fixed indefinitely. They concluded that “a rogue planet could disrupt the orbits of detectable planets.” We are just beginning to understand ISOs and stray planets. We know they are there, but we don’t know their numbers or where they are. The Vera Rubin Observatory can open our eyes to this collection of objects. It may even show how they cluster in some areas and avoid others. According to this study, if it is near any of the openings in the Sun Hill sphere, we may have a visitor who chooses to stay.