A powerful new observatory is the best hope yet for finding the elusive Planet 9, a large planet that some scientists say is ...

Discover the order of planets in the solar system ... system The solar system formed about 4.6 billion years ago from a giant rotating cloud of gas and dust known as the solar nebula.

Mike Brown is convinced that beyond Neptune, at the far reaches of our solar system, there's an unseen giant planet. "This is the 5th largest planet in our solar system, lurking out there ...