Near-UV Reddening Observed in the Reflectance Spectrum of High-inclination Centaur 2012 DR₃₀

Abstract

Centaurs with high orbital inclinations and perihelia (i > 60°; q ≳ 5 au) are a small group of poorly understood minor planets that are predicted to enter the giant planet region of the solar system from the inner Oort Cloud. As such, they are one of the few samples of relatively unaltered Oort Cloud material that can currently be directly observed. Here we present two new reflectance spectra of one of the largest of these objects, 2012 DR30, in order to constrain its color and surface composition. Contrary to reports that 2012 DR30 has variable optical color, we find that consistent measurements of its spectral gradient from most new and published data sets at 0.55–0.8 μm agree with a spectral gradient of S ′ ≃ 10 % ± 1 % / 0.1 μ m within their uncertainties. The spectral variability of 2012 DR30 at near-UV/blue and near-IR wavelengths, however, is still relatively unconstrained; self-consistent rotationally resolved follow-up observations are needed to characterize any spectral variation in those regions. We tentatively confirm previous detections of water ice on the surface of 2012 DR30, and we also consistently observe a steady steepening of the gradient of its spectrum from λ ∼ 0.6 μm toward near-UV wavelengths. Plausible surface materials responsible for the observed reddening may include ferric oxides contained within phyllosilicates and aromatic refractory organics.

The Transition from the Kuiper Belt to the Jupiter-Family (Comets)

“…pend on the amount of dehydrogenation of the organic, how disordered the molecular structure is, and the level of nonorganic contaminant in the molecular chains, in particular (Seccull et al 2021). This feature is common to many organic materials that are considered suitable astrophysical analogs; compare the chemically simple polycyclic aromatic hydrocarbons (e.g., Izawa et al 2014) to the highly disordered laboratory materials called tholins (e.g.. Roush and Dalton 2004), both of which show this deep optical gap.…”