Planet 9 is a hypothetical, undiscovered "super-Earth" or "mini-Neptune" planet believed to exist in the extreme outer Solar System, far beyond Neptune. Proposed by Caltech astronomers in 2016 to explain the peculiar, clustered orbits of icy Kuiper Belt objects, it is thought to be 5–10 times the mass of Earth. Key Details about the Planet 9 Hypothesis: Orbit: It likely follows a highly elongated (elliptical) orbit, taking 10,000 to 20,000 years to complete one revolution around the Sun. Location: It is estimated to be 400–800 AU (astronomical units) from the Sun, making it incredibly faint and difficult to detect. Evidence: Its existence is not confirmed, but its gravitational influence is believed to be pulling smaller, distant, icy bodies (trans-Neptunian objects) into odd, tilted, and "backward" orbits. Origin: Scientists suggest it could be the core of a giant planet ejected by Jupiter early in the solar system's history, or a planet captured from another star. Search Status: Astronomers are actively searching for it using data from infrared surveys and tools like the upcoming Vera Rubin Observatory, but no direct evidence has been found yet. While nicknamed "Planet 9," it is technically a distinct concept from the historical search for "Planet X" or the now-demoted Pluto
