Are there ‘stray’ planets in our solar system that we don’t know about?

Are there ‘stray’ planets in our solar system that we don’t know about?
While we seem to know our solar system very well, our clear understanding of what’s going on around and beyond Neptune is based on only a few spacecraft and observations.
In fact, it’s very difficult to observe this region, which is so far from the Sun that it’s usually blocked from our star’s light.
The Kuiper Belt, a region beyond Neptune that is home to dwarf planets like Pluto, Eris, and Haumea and is made up of many small, icy rocks, is known as the most unknown region of our system. Even further out, there is thought to be a giant, spherical region of small rocks called the Oort Cloud, whose exact size is unknown. But theoretical astrophysicist Amir Siraj suggests that there could be other objects in this region that we haven’t yet noticed. Siraj, of Princeton University, says that according to his projections, there could be planets 1.2 the size of Mars, 2.7 the size of Mars, and 5.2 the size of Mercury. According to Siraj, these planets are not leftovers from the performance of the Solar System, but are stuck in this region from the systems of other alien stars.
The idea of ​​a “rogue planet”, first scientifically put forward in 2000, is not impossible when considering gravitational interactions. It is thought that such planets wander around the galaxy after breaking away from their stars. How common this phenomenon is is still being monitored. It is even thought that the Kepler Space Telescope, which arrived at the end of 2018, may have found a few of them. Perhaps with more advanced technological observations, we will be able to understand how common these planets are.

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