Forbidden planet: was Pluto’s 2006 demotion a big mistake?
Since it was stripped of planetary status, Pluto’s defenders have been fighting the decision – and they’re only getting more passionate
TL;DR
- Pluto was demoted from planet to dwarf planet status by the IAU in 2006, reducing the solar system's planet count to eight.
- Many scientists argue that the IAU's definition of a planet, particularly the "cleared its neighbourhood" criterion, is scientifically flawed and not useful.
- The debate has intensified over the past two decades, with a campaign to reinstate Pluto as a planet, largely driven by public affection and a sense of wounded pride in the US where Pluto was discovered.
- The discovery of Eris, another celestial body in the Kuiper Belt similar in size to Pluto, prompted the IAU's re-evaluation and the need for a new planet definition.
- The controversy highlights a split between "geophysical" and "dynamicist" views on planethood, with some scientists advocating for a definition based on physical characteristics and others on orbital dynamics.
- Critics of the IAU definition point out that its criteria could disqualify Earth if moved to Pluto's orbit and that orbit clearing is not a universally meaningful category.
- Proponents of reinstatement welcome a broader definition, comparing the potential number of planets to Pokémon species, while opponents worry about including bodies like the Moon, which would meet geophysical criteria but were long ago deemed not planets.
- The debate also touches on procedural questions about the IAU vote itself, with some arguing it was incorrectly conducted.
- Advocates believe that Pluto's demotion hindered scientific education by presenting an outdated, orderly view of the solar system rather than a more modern, chaotic one.
- The historical context of Pluto's discovery and its initial misclassification as Planet X is also relevant to its complex reputation.