Is there a hidden 'Planet 9' in our solar system?

For more than a century, astronomers have been captivated by the idea that an undiscovered planet could be lurking in the furthest reaches of our solar system.The search for this elusive, hypothetical planet has taken many forms over the decades. The discovery of Neptune in 1846 demonstrated that an unseen planet might be inferred from its gravitational effects on other worlds. Based on this, the search for a ninth planet began in earnest, seemingly culminating with the discovery of Pluto by ast