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RESEARCH PRODUCT

Col-OSSOS: Colours of the Outer Solar System Origins Survey

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description

International audience; The surfaces of trans-Neptunian objects (TNOs) are poorly understood. Other than the large objects which exhibit signatures of various ices, very little has been discerned about the compositions of most TNOs. In recent years, some concrete knowledge about the distribution of surface colours of small TNOs has come to light. It is now generally accepted that small TNOs fall into at least three classes of object based on their surface colours and albedo. TNO surface type is also correlated with dynamical class, with certain types of TNO being found primarily in certain regions of the outer Solar System. This correlation presents the intriguing idea that the surfaces of TNOs contain information on more than composition, but as well hold the key to understanding the dynamical processes that lead to the giant planets violently dispersing the protoplanetesimal disk and populating the Kuiper Belt region. It is around this idea that the Col-OSSOS survey is predicated. This 4 year program which started in 2014B is simultaneously using the Gemini-North and Canada-France-Hawaii telescopes to gather near simultaneous u, g, r, and J spectral photometry of all targets in the Outer Solar System Origins Survey (OSSOS) brighter than r’=23.5 (~140 expected). The focus of Col-OSSOS is completeness and consistency, with the same SNR=25 being reached in all bands, for all targets brighter than our depth limit.Col-OSSOS will provide a combined compositional-dynamical map from which key hypotheses about the Solar System's cosmogony can be tested. For example, by mapping the fraction of TNOs with cold-classical like surface colours, we will be able to determine how much of the belt was populated by dynamical scattering versus sweep-up from Neptune. Further, we will be able to constrain the compositional homogeneity of the protoplanetesimal disk. The surfaces of TNOs must reflect that homogeneity; a heterogeneous disk will result in a clumpy colour distribution with many unique types, while a homogeneous disk will result in a smooth distribution of colours with only a few distinct types. Here we will present preliminary results and report on the initial progress of the survey.