Astronomers want to change how we define a planet — again
![Astronomers want to change how we define a planet — again](https://cdn.mos.cms.futurecdn.net/GuYEwVMfA8HwScNAHp3rsC.jpg)
Astronomers are proposing a new, more quantitative definition of what makes a planet. The new definition looks more directly at the object's mass — but it would still leave Pluto out of the running.