Published on 27 Sep 2013
The comet’s formal designation is C/2012 S1. The “C” indicates that it is non-periodic, followed by the year of discovery. The “S” represents the half-month of discovery—in the case of C/2012 S1, the second half of September—and the number “1” shows that this was the first comet found in that half month. The addition of “(ISON)” after its name merely identifies the organization where its discovery was made, the Russia-based International Scientific Optical Network. If the same organization had discovered a similar, but unrelated comet one day later, that one would have been named “C/2012 S2 (ISON)”. Nevertheless, media sources have taken to referring to C/2012 S1 by its location of discovery, and consequently, this name will likely persist in use even though it may cause confusion with later discoveries made by the ISON organization. The names of famous short-period comets usually identify the astronomers who discovered them or clearly identified them as a periodic comet, such as Halley’s Comet or Comet Swift–Tuttle. If that convention had been followed, “Comet ISON” would be referred to instead as Comet Nevski–Novichonok or C/2012 S1 (Nevski–Novichonok).