Cometia

Cometia is a term that appears in speculative astronomy and science fiction to designate a hypothetical class of small solar-system bodies with comet-like activity. It is not an officially recognized taxon by the International Astronomical Union, and there is no widely accepted formal definition. The concept is used to discuss objects that exhibit cometary behavior while deviating from traditional classifications of comets or asteroids.

Derived from comet, with the -ia suffix common in taxonomic labels, Cometia in fiction and speculative writing often refers to icy bodies with hybrid properties, such as persistent outgassing beyond the usual perihelion distance, unusual dust-to-gas ratios, or orbital characteristics that challenge simple categorization.

Because Cometia lacks an official definition, real-world usage varies. Proposals typically involve a combination of orbital parameters (eccentricity, inclination, and period) and activity indicators (outgassing rates, coma development, and spectral features). No object has been formally designated Cometia in scientific catalogs, and any future recognition would require reproducible measurements and consensus within the astronomical community.

In culture, the term serves as a convenient placeholder to explore transitional bodies between asteroids and comets and to illustrate how solar-system classifications may evolve.