Mercury. Jupiter. Even Pluto. All solid, no-nonsense names. 2003 UB313 doesn’t quite have the same ring to it, somehow. But that’s the moniker scientists plumped for, and hey, it beats Goofy, I suppose. Any time a new transplutonian object larger than Pluto itself is discovered, people start disrespecting poor old Pluto, saying that it should never have been classified as a planet in the first place, but rather as a mere planetoid (i.e., somewhere between a planet and an asteroid). DDC-using Pluto fans can rest easy, though -- we’re not going to downgrade it. Yet. But there’s another question: Does the discovery of this new "new" 10th planet (not to be confused with the discovery of the old "new" 10th planets -- e.g., 2004 DW, 2003 VB12, and 2002 LM60) mean we editors are all a-fluster, scrabbling around for a spare DDC number for it? Not exactly. At 523.4 Planets of solar system, Neptune and Pluto are already both classed under 523.48 Trans-Uranian planets, at 523.481 and 523.482 respectively. Meanwhile, back in Table 2, at —99 Extraterrestrial worlds, notation —9929 is used for Pluto and transplutonian planets. So we’re covered for now. But we’ll be monitoring the situation: If the new new 10th planet really does start to be accepted as the 10th planet, we’ve got 523.483 washed, dressed, and ready to go. And at some point we might need to revisit* Pluto, and decide whether it is a true planet or just one of many Kuiper belt objects.
* Not literally.