Many of you, like myself, were probably taught in grade school that Pluto was the ninth planet in our solar system, and, ...

Known as Planet Nine or Planet X, it is a hypothetical planet that has ... a wealthy American businessman and astronomer, kicked off the search for it in 1906. For more than 70 years, Pluto ...

Caltech researchers have mathematical evidence suggesting a Neptune-sized Planet X may exist deep in the solar system in an orbit far beyond Pluto. Planet X could have a mass about 10 times that of ...