Is there a ninth planet? The verdict of Nasa's chief scientist - BBC Newsnight

New research has emerged which suggests there could be a ninth planet http://bbc.in/1S6ENQf. How convincing is the evidence? We asked Nasa's chief scientist Ellen Stofan. ********** Newsnight is the BBC's flagship news and current affairs TV programme - with analysis, debate, exclusives, and robust interviews. Subscribe to our YouTube channel for highlights and bonus videos http://bbc.in/1iouM30 Follow us on Twitter @BBCNewsnight for the latest updates on #newsnight Add us on Snapchat - our username is 'BBCNewsnight' And follow on Facebook for our best material, an early heads up on what's coming up, and to join in our debates https://www.facebook.com/bbcnewsnight