Scientists have been debating the existence of "Planet Nine," a mysterious object believed to exist in the outer reaches of our solar system. First hypothesized in 2016 by astronomers Konstantin Batygin and Michael Brown, this hypothetical planet is thought to be about 10 times the mass of Earth, orbiting far beyond Neptune. Its orbit is extremely elongated, taking between 10,000 to 20,000 years to circle the Sun. Planet Nine’s existence is inferred from the unusual behavior of objects in the Kuiper Belt, a region filled with icy bodies and dwarf planets. Several Kuiper Belt objects (KBOs) follow strange orbits, which some scientists believe can only be explained by the gravitational pull of a massive unseen planet. Despite its size, Planet Nine has been difficult to detect because it reflects very little sunlight, making it nearly invisible to most telescopes. Some astronomers even propose that it could be a primordial black hole, adding another layer of complexity to the search.