Category: IAU

This Is Everything That’s Wrong With Our Definition Of ‘Planet’

“There are many people who would love to see Pluto regain its planetary status, and there’s a part of me that grew up with planetary Pluto that’s extraordinarily sympathetic to that perspective. But including Pluto as a planet necessarily results in a Solar System with far more than nine planets. Pluto is only the 8th largest non-planet in our Solar System, and is clearly a larger-than-average but otherwise typical member of the Kuiper belt. It will never be the 9th planet again.

But that’s not necessarily a bad thing. We may be headed towards a world where astronomers and planetary scientists work with very different definitions of what attains planethood, but we all study the same objects in the same Universe. Whatever we call objects — however we choose to classify them — makes them no less interesting or worthy of study. The cosmos simply exists as it is. It’s up to the very human endeavor of science to make sense of it all.”

Next month will mark 13 years since the International Astronomical Union (IAU) officially defined the term planet and ‘Plutoed’ our Solar System’s (up-until-that-point) 9th planet. With an additional 13 years of knowledge, understanding, data, and discoveries, though, did they get the decision right?

Certainly, there were aspects that needed to be revised, but the IAU’s definition comes along with some major gaps and mistakes. We can do better! Come learn how.