Astronomers are closing in on one of the most tantalizing possibilities in planetary science, evidence that a previously unknown world may be lurking in the outer reaches of the solar system. The ...

(CNN) — 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 ...

To date, humanity has discovered over 6,200 confirmed exoplanets, or planets outside of our solar system, according to NASA's ...

Even at a glance, the planets in our solar system are wildly diverse. Huge and small, airless and densely packed with ...