Pluto’s inbox is filling up with awkward NASA apology emails today.
After an eight year exile from the list of technical planets in our solar system, Pluto might be making its way back as our ninth celestial next-door neighbor.
Pluto’s journey through planethood started with its discovery and subsequent admission as our tiny ninth planet back in 1930. Skeptics emerged in 1977, when satellites showed that Pluto wasn’t just small, it wasn’t even the biggest planet in its orbit. Space truthers lurked around the astronomy community until they finally had their day in court during anInternational Space Union (IAU) conference in 2006. At the conference, officials outlined requirements for planet designation, including:
- Orbit around the sun
- Have sufficient mass to assume hydrostatic equilibrium (science talk for “the planet must be round”)
- Have “cleared the neighborhood” around its orbit (science talk for “must be the biggest thing in its orbit”)
Pluto orbits the sun and has a round shape, but it isn’t the biggest planet in its orbit (neighboring Eris is 27% bigger). The IAU voted 9-8 for its removal, declassifying Pluto as a planet. The science community was forced to take Pluto off the list of technical planets and space geeks felt like that kid from Old Yeller for the day.
Eight years later, and Pluto may get a chance to reclaim its planetary spot in our solar system.
Standing behind the logic that “Even though a dwarf fruit tree is still a small fruit tree, and a dwarf hamster is still a small hamster,” The Harvard-Smithsonian Center for Astrophysicsrecently decided to revisit the IAU’s ruling by hosting a discussion on the definition of a planet. Three experts chimed in on the controversy: Dr. Owen Gingerich, chair the IAU planet definition committee; Dr. Gareth Williams, associate director of the Minor Planet Center; and Dr. Dimitar Sasselov, director of the Harvard Origins of Life Initiative.
“Gingerich argued that ‘a planet is a culturally defined word that changes over time,’ and that Pluto is a planet. Williams defended the IAU definition, which declares that Pluto is not a planet. And Sasselov defined a planet as ‘the smallest spherical lump of matter that formed around stars or stellar remnants,’ which means Pluto is a planet.”
So there you have it. Pluto is back in… sort of.
The vote wasn’t official and doesn’t really hold any actual weight in the science community but it’s a start and you know that ol’ science adage: “Space Rome wasn’t built in a single zettasecond.”
by Eitan Levine