Kirk Borne

Pluto lost its planet status 20 years ago. Of the three criteria for planethood, Pluto meets the first two qualifications: it orbits the sun and is round. But it fails the third because it hasn’t cleared its celestial “neighborhood,” meaning it is actually a dwarf planet. Yeah, that's a hard astrophysics requirement, not a soft emotional one. “Plutokiller” Mike Brown explains the ongoing drama: https://magazine.caltech.edu/post/pluto-lost-its-planethood-20-years-ago-plutokiller-mike-brown-explains-the-ongoing-drama?utm_medium=email&utm_campaign=magazine-spr26&utm_source=caltechmagazine&utm_content=&utm_term=