Review of asteroid literature suggests voting isn't right way to define planetary status
© NASA, JHUAPL, SwRI
The International Astronomical Union’s vote in 2006 to demote Pluto to dwarf planet status merely created “the illusion of scientific consensus,” according to a recent paper.
If Dr. Seuss had been an astronomer, Horton the Elephant (who heard a Who) would have said "a planet's a planet, no matter how small."
Even Pluto.
But don't quote Dr. Seuss to the International Astronomical Union. In 2006, the IAU declared Pluto a planet not.
IAU
Resolution B5 (not to be confused with Le Petit Prince's asteroid B 612) declared that in order to be considered a planet, a body must clear the neighborhood around its orbit. Pluto, then, doesn't qualify, because its "neighborhood" (way out beyond the orbit of Neptune) is populated by other bodies referred to as trans-Neptunian or Kuiper Belt objects. Two of them, Haumea and Makemake, have been recognized as "dwarf planets," the same designation that the IAU now applies to Pluto.
This demotion of Pluto to dwarf status (no offense intended to dwarfs) makes sense, IAU defenders contend, because the asteroids (orbiting the sun mostly between Mars and Jupiter) aren't planets, either - no one of them has cleared out the orbital neighborhood. After all, nobody would call an asteroid a PLANET. Except actually, nearly everybody called them planets for 150 years after they were discovered.
Only half a century or so ago did astronomers stop considering most asteroids to be planets. And that shift had nothing to do with clearing out any neighborhoods, Philip Metzger of the University of Central Florida and colleagues point out
in a new paper.
Comment: One wonders, were those fault lines always there and moving at that rate, or has something changed?