Diaphanitas

New information about Pluto:

Scientists decide Pluto’s no longer a planet

PRAGUE, Czech Republic - Leading astronomers declared Thursday that Pluto is no longer a planet under historic new guidelines that downsize the solar system from nine planets to eight.

But it's good that the IAU didn't do the "classical planet" thing.

The IAU therefore resolves that "planets" and other bodies in our Solar System be defined into three distinct categories in the following way:

(1) A "planet"1 is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape2 , (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

(3) All other objects3 except satellites orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".

1The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
2An IAU process will be established to assign borderline objects into either dwarf planet and other categories.
3These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.

So, Pluto is just a special kind of planet... a "dwarf planet."

What does this mean for Sailor Pluto (Setsuna)? Her planet is no longer considered a major planet, but that doesn't mean that she cannot still be a sailor soldier representing Pluto.

• There is no "an individual can be a sailor soldier only if she represents a planet" rule. (The moon is not a planet according to the IAU, and there is at least one sailor soldier representing it. Eventually, there are two.)
  
  
• Sailor soldiers can represent hoshi (or hoshiboshi), which means, in this case, "celestial bodies," and that includes planets and moons.
  
  
• In the BSSM continuities, Pluto is one of the planets in the solar system.
  
  
• In real life, Pluto is not one of the major eight planets, but that does not necessarily mean it's not a planet of any sort.

LWotP: Pluto -onis m. "Pluto."