In 2016, astronomers published a study suggesting a ninth planet could be hiding on the edge of our Solar System. Eight years later, they're still looking for it. So what will it take to find it?
New evidence for Planet 9 at the fringes of our solar system earthsky.org - get the latest breaking news, showbiz & celebrity photos, sport news & rumours, viral videos and top stories from earthsky.org Daily Mail and Mail on Sunday newspapers.
Evidence builds for Planet Nine lurking somewhere out there astronomy.com - get the latest breaking news, showbiz & celebrity photos, sport news & rumours, viral videos and top stories from astronomy.com Daily Mail and Mail on Sunday newspapers.