Spectral information of K2 extracted over two different aperture radii. (a) Unbinned spectrum of the K2 coma (with a step of 1.25 Å) extracted over smaller (corresponding to the cometocentic distance ρ of ≈10³ km; green) and larger (ρ ≈ 2 × 10⁴ km; purple) radius circular apertures. (b) Relative reflectance of K2 normalized at 6000 Å. Its spectra are binned to match the spectral resolution (5 Å) of the solar spectrum. Three arrows indicate significant emission features of gas species: the C₂(0,0) band at ~5100 Å, the OI¹D line at 6300 Å, and the CN(1,0) red band at ~9200 Å. The circles and diamonds are the data of K2 taken at r_H ~15.5 and ~15.4 au, respectively (Meech et al. 2017).