The Solar System is far more diverse in size than it appears from Earth. From tiny rocky worlds to massive gas giants, each planet differs dramatically in scale. To truly understand these differences, ...

Astronomers believe they have uncovered evidence of a previously unknown ninth planet lurking in the not-too-distant reaches of the solar system. This hypothetical world, dubbed "Planet Y," could be ...

The search for an unknown planet in our solar system has inspired astronomers for more than a century. Now, a recent study suggests a potential new candidate, which the paper’s authors have dubbed ...

Is there a massive undiscovered planet on the outer reaches of the Solar System? The idea has been around since before the discovery of Pluto in the 1930s. Labelled as planet X, prominent astronomers ...