BY: PHILIPPE DE JOCAS
Quick! Name the planets!
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune… and Pluto? Except – as any child of the 2000s will tell you – Pluto’s not a planet, at least not anymore.
In 2006, astronomers came to the conclusion that Pluto wasn’t a planet, but merely a “dwarf planet.” Pluto found a new career as the de- facto mascot of the dwarf planets and their ilk: a group of planetoids and chunks of rock that lurk at the very fringes of our solar system. Now a dedicated campaign spearheaded by a small but vocal group of scientists aim to restore Pluto’s old glory.
7.5 billion kilometers away from the sun, the world of Pluto lies too far away to receive any real light from the star that it orbits. It and its five moons – Charon, Styx, Kerberos, Nix, and Hydra – dance a lonely tango at the very edge of known space. As an astronomical body, Pluto holds the dubious honor of being both the last planet discovered and the planet to hold that title for the shortest amount of time. In 1905, American astronomer Percival Lowell – you might know him as the father of the infamous “Martian canals” theory – became convinced of the presence of a ninth planet in the solar system as he charted the eccentric orbits of Uranus and Neptune. Though Lowell died before he could discover this mysterious planet, his theories remained, and other scientists took up his search for the not-at-all-melodramatically named “Planet X.” It took 25 years of patient studying before Illinois astronomer Clyde Tombaugh found Pluto. An 11-year-old girl from Oxford suggested the moniker in honor of the mythical Greek god of the underworld – not Mickey’s faithful pooch.
Over the years, as we started launching rockets and exploring the fringes of our solar system, we have learned that our solar system hosts a wide variety of stellar objects quite apart from planets. Astronomers started calling them “dwarf planets:” too big for asteroids, too small for planets. In 2005, we discovered the wee world of Eris, a rocky world 27% more massive than Pluto. Then things started getting complicated. Like a horseman of the apocalypse, Eris heralded the discovery of dozens of other tiny dwarf planets swarming at the edge of our solar system, with names straight out of a Dungeons and Dragons campaign: Sedna, Makemake, Quaoar, Orcus, Vanth, to name a few. The discovery of this cosmic zoo of dwarf planets sent ructions through the scientific community. Should Eris become the tenth planet? And if so, what about Orcus or Quaor? Where do we draw the line? Should we downgrade Pluto to a dwarf planet instead? In 2006, astronomers convened, weighed the evidence, and decided on the latter option. Pluto’s sudden and unprecedented “demotion” came as a shock to the public, and before long it became a running joke in popular culture.
Eleven years later, however, a group of scientists hope to undo the change and take Pluto back, promoting it back to its original position as the last planet in the Solar System. Six astronomers from across the United States have presented a paper explaining what, in their opinion, sets Pluto apart from its dwarf contemporaries. To them, it’s not just the size that counts – it’s what you do with it. Pluto, they argue, sports many distinct geographical and topographical features, including rugged mountain ranges and virtual “oceans” of low-lying land. Its contemporaries such as Eris, the world that set off this whole debate in the first place, lack any real distinct geographic features save for rolling, rocky, and virtually featureless plains. Will this ballsy proposal succeed in making the case for poor Pluto? Stay tuned…