We have discovered thousands of exoplanets in the last few decades, while the number of planets in the Solar System has remained at eight – but our discovery of more might not yet be over.

The solar system may hold a hidden surprise. Astronomers are investigating the possibility of a mysterious ninth planet, often referred to as Planet Nine. If found, this discovery could change the ...

Astronomers are trying to solve one of the biggest mysteries in space: Is there a hidden ninth planet in our solar system? This planet, called “Planet Nine,” could be far beyond Neptune ...