Two faint objects hiding in archival infrared sky maps now sit at the center of a growing scientific argument about whether a ...

A newly discovered object orbiting far beyond Neptune has its closest approach to the Sun pointed in the opposite direction from every other known body like it, weakening one of the central ...

As the United States prepares to celebrate its 250th anniversary, the history of the solar system tells its own story of ...

What is Planet Nine, and where is it? The question has fascinated astronomers for years. Scientists believe a massive undiscovered planet may exist in the outer Solar System. Although no telescope has ...