Searching for Planet X

Is there an undiscovered planet playing hide-and-seek beyond Neptune?

- 

Our solar system is home to eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. However, for over a century there’s been speculation of another possible planet, known as Planet X, lurking in the distant solar system. This may sound far-fetched, but some astronomers think it’s real. There’s a catch, though – telescopes have yet to find Planet X, so does it actually exist? The search is on to solve the mystery.

The search begins

After the discovery of Neptune in 1846, astronomers began searching for more planets. US businessman and amateur astronomer Percival Lowell thought the gravity of an elusive Planet X was affecting the orbits of Uranus and Neptune as they circled the Sun. His search efforts, starting in 1905, were unsuccessful.