The Kuiper Belt Object (KBO) 90377 Sedna

90377 Sedna, a mysterious Kuiper Belt Object, baffles astronomers with its extraordinary 11,400-year elliptical orbit extending 937 AU from the Sun - far beyond Neptune's influence. This reddish, planet-sized body's extreme path suggests possible unknown gravitational forces or a distant undiscovered planet shaping its trajectory. Discovered in 2003, Sedna never comes closer than 76 AU to the Sun, making it one of the coldest known objects in our solar system. Its existence challenges current solar system models, fueling theories about the early solar system's formation and the potential presence of a massive "Planet Nine" in our system's outer reaches.