COSINE (Cometary Object Study Investigating Their Nature and Evolution). I. Project Overview and General Characteristics of Detected Comets
October 2025 • 2025ApJS..280...67K
Abstract • We present the first results from the Cometary Object Study Investigating their Nature and Evolution (COSINE) project, based on a uniformly processed data set of 484 comets observed over the full 15 yr duration of the Wide-field Infrared Survey Explorer (WISE)/NEOWISE mission. This compilation includes 1633 coadded images spanning 966 epochs with signal-to-noise ratios greater than 4, representing the largest consistently analyzed infrared comet data set obtained from a single instrument. Dynamical classification identifies 234 long-period comets (LPCs) and 250 short-period comets (SPCs), spanning heliocentric distances of 0.996─10.804 au. LPCs are statistically brighter than SPCs in the W1 (3.4 μm) and W2 (4.6 μm) bands at comparable heliocentric distances. Cometary activity peaks near perihelion, with SPCs exhibiting a pronounced postperihelion asymmetry. Multiepoch photometry reveals that SPCs show steeper brightening and fading slopes than LPCs. The observing geometry of WISE/NEOWISE—constrained to a fixed ∼90° solar elongation from low-Earth orbit—introduces systematic biases in the sampling of orientation angles for extended features. Collectively, the results reveal a continuous evolutionary gradient across comet populations, likely driven by accumulated solar heating and surface processing. This study establishes a foundation for subsequent COSINE analyses, which will separate nucleus and coma contributions and model dust dynamics to further probe cometary activity and evolution.
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