The Pluto problem: Is it time to rethink our definition of a planet? 

 In 2006, the International Astronomical Union (IAU) famously demoted Pluto to a dwarf planet. Things have been a bit of a mess since then — so is it time to redefine the planet?  

https://cdn.mos.cms.futurecdn.net/qVLgBbgNB2i7uafbCjWYmi.jpg

https://www.space.com/pluto-problem-time-to-rethink-definition-of-a-planet