when pluto was a planet

or, the age of innocence from an astronomer's point of view

for 76 years, kids in school have learned that our solar system has 9 planets: mercury, venus, the earth, mars, jupiter, saturn, uranus, neptune and pluto. first the four "rocky" ones, small and made out of solid material. then the four "giant" ones, much more massive and made out of a dense mixture of gaseous elements. and then, there was pluto.

pluto was the last one to be discovered, in 1930, and has always had the charm of an outsider. it is the farthest of the sun's court, but not always: its orbit is in fact very eccentric, and crosses the one of neptune, so that the two switch regularly in being the most distant from the sun. another weird fact about pluto is that it is rocky and tiny, like the earth-like planets, and unlike its closer, giant neighbours.

when pluto was still a planet, it also had a satellite, charon. charon was identified as a satellite only because it had been discovered more than 40 years later after pluto, but it would have been more appropriate to refer to them as a double planet system: contrarily as for all other satellites, the mass of charon is not significantly smaller than that of pluto.

then, the past decade witnessed new discoveries: quaoar, sedna and eris, all objects with masses and orbits very similar to pluto's. who knows how many other pluto-like bodies future observations will report. not being able to ignore the new discoveries, but also trying to prevent the number of solar system planets to increase dramatically, the international astronomical union called a halt and came out with an official definition for a planet.

the new definition involves not only being a celestial body orbiting the sun with a nearly spherical shape, but also being the object which contains most of the mass in its own orbit.
not being much larger than its fellow charon, pluto did not fulfill the definition, thus ceased being a planet in 2006.

i grew up with the dream of becoming an astronomer, thinking that the practice of such a pure science was the highest step of human knowledge. not that it mattered much, but at the time i was also aware that i was living in a special planet out of a set of nine. then i started moving my first steps in the world of astronomy and astrophysics, still amazed by the idea of research. i was walking along the twilight zone, uncertain about how to cross it, and suddenly pluto was not a planet anymore. reality was there to be faced: science was no more the purest of all things, it is in fact just a human matter. it was not as neat as i thought, but most importantly i learned how it isolates the individuals who practice it from the rest of the world. i started wondering if this price is worth the game. and i'm still wondering. the age of disillusion.

right after the end of pluto's career as a planet, the american dialect society chose "to pluto" as word of the year. it's supposed to mean "to deprive something of its value". along with the former ninth planet, also my dream was plutoed. but i decided to restore its value. i realised science was not what i had expected, but i chose to deal with it, to adjust my dream and take the most i could from it. pluto is now a dwarf planet. let's see what happens to me and science.