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

TL;DR

This study analyzes the reflectance spectrum of Centaur 2012 DR30, confirming its consistent spectral gradient and potential surface composition, including water ice and reddening materials, to better understand its origin and surface properties.

Contribution

First spectral analysis of 2012 DR30 confirming its consistent color and identifying potential surface materials, including water ice and reddening agents.

Findings

Spectral gradient of ~10%/0.1 micron consistent across datasets.

Tentative detection of water ice on the surface.

Observed spectral steepening towards Near-UV wavelengths.

Abstract

Centaurs with high orbital inclinations and perihelia (i > 60 degrees; q >= 15 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 datasets at 0.55-0.8 micron agree with a spectral gradient of S ~ 10+/-1 %/0.1 micron within their uncertainties. The spectral variability of 2012 DR30 at Near-UV/blue and Near-Infrared wavelengths, however, is still relatively unconstrained; self-consistent rotationally resolved followup observations are needed to characterise any spectral variation in those regions. We tentatively confirm previous detections of water ice on the surface of 2012 DR30 , and also consistently observe a steady steepening of the gradient of its spectrum from wavelengths of around 0.6 micron towards Near-UV wavelengths. Plausible surface materials responsible for the observed reddening may include ferric oxides contained within phyllosilicates, and aromatic refractory organics.