Col-OSSOS: A new ugrJ taxonomy for trans-Neptunian objects
Abstract
The surfaces of trans-Neptunian objects (TNOs) are poorly understood. Very little has been discerned about the compositions of most small TNOs. In recent years however, some concrete knowledge about the surface colour distribution of 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. Despite nearly two decades of gathering TNO surface information however, a taxonomy has still not been agreed upon. From Col-OSSOS u, g, r, and J photometry, we find significantly different clustering of (u-g) colour in the optically red, dynamically cold TNOs as compared to similarly optically coloured dynamically excited TNOs. One of the goals of the Colours of the Outer Solar System Origins Survey is the development of a robust TNO taxonomy. 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'=23.6 (120 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 the first brightness-complete, compositional-dynamical map of the Outer Solar System, from which key hypotheses about the Solar System's cosmogony can be tested. After an overview of the survey's design and techniques, we will present the observed colours from the first complete block. Even with just ~30 targets, the precise photometry afforded by Col-OSSOS has already revealed the existence of 3 separate TNO taxons or classes, which become obvious when their (u-g), (g-r), and (r-J) colours are considered together. In particular, the so-called cold classical TNOs, which stand out because of their dynamically quiescent orbits, while possessing similar (g-r) and (r-J) colours as other red TNOs, exhibit extremely red (u-g) colours, roughly 0.5 magnitudes redder than the typical (u-g) of the red dynamically excited objects. These classes appear to exhibit a continuum in colour, rather than occupying similar mean colours for all class members.
- Publication:
-
AAS/Division for Planetary Sciences Meeting Abstracts #48
- Pub Date:
- October 2016
- Bibcode:
- 2016DPS....4811302F