Scientists believe that there is an undiscovered massive planet lurking at the edge of the Solar System. Join researchers as they hunt for this mysterious world, an investigation that could reveal the secret history of the Solar System's formation. <br /><br />Thanks for watching. Follow for more videos. <br />#cosmosspacescience <br />#spacedeepestsecrets <br />#season2 <br />#episode7 <br />#cosmology <br />#astronomy <br />#spacetime <br />#spacescience <br />#space <br />#nasa <br />#spacedocumentary <br />#darkmatter <br />#planet9 <br />#oursolarsystem <br />
