The relative reflectance spectrum of (90377) Sedna (black circles) and the spectrum of the nearby sky

The relative reflectance spectrum of (90377) Sedna (black circles) and the spectrum of the nearby sky (grey circles). Gray curves are the model 3 σ upper limits to the surface fraction of water ice (smooth gray line) and methane ice (jagged gray line). Surface fractions that cause more absorption than the indicated lines are ruled out by our observations at the 3 σ level. The model shown is for 100-micron diameter particles. Spectrum error bars are computed from the reproducibility of the spectral data in each spectral point.