OSSOS

Nahuel Cabral,Ying-Tung Chen,Kathryn Volk,Brett Gladman,Michaël Marsset,Jean-Marc Petit,Philippe Rousselot,Stephen D J Gwyn,Michele T Bannister,John J Kavelaars,Aurélie Guilbert-Lepoutre,Wesley C Fraser,Mike Alexandersen

doi:10.1051/0004-6361/201834021

Abstract

Context. Centaurs are icy objects in transition between the trans-Neptunian region and the inner solar system, orbiting the Sun in the giant planet region. Some centaurs display cometary activity, which cannot be sustained by the sublimation of water ice in this part of the solar system, and has been hypothesized to be due to the crystallization of amorphous water ice. Aims. In this work, we investigate centaurs discovered by the Outer Solar System Origins Survey (OSSOS) and search for cometary activity. Tentative detections would improve understanding of the origins of activity among these objects. Methods. We search for comae and structures by fitting and subtracting both point spread functions and trailed point-spread functions from the OSSOS images of each centaur. When available, Col-OSSOS images were used to search also for comae. Results. No cometary activity is detected in the OSSOS sample. We track the recent orbital evolution of each new centaur to confirm that none would actually be predicted to be active, and we provide size estimates for the objects. Conclusions. The addition of 20 OSSOS objects to the population of ~250 known centaurs is consistent with the currently understood scenario, in which drastic drops in perihelion distance induce changes in the thermal balance prone to trigger cometary activity in the giant planet region.

Highlights

Centaurs are a population of icy objects orbiting the Sun in the giant planet region: they are typically defined as having a perihelion distance between 5.2 and 30 au, and a semi-major axis below 30 au (Jewitt 2009)
We can even argue that the orbital evolution of Outer Solar System Origins Survey (OSSOS) centaurs is consistent with it, since none fits the thermal requirements for triggering crystallization-driven activity
We further argue that if crystallization is the source of cometary activity amongst centaurs, it would favour activity on objects dynamically new to the Jupiter–Saturn region, as objects having previously stayed in this region would have exhausted their amorphous water ice in the near-surface layers

Summary

Introduction

Centaurs are a population of icy objects orbiting the Sun in the giant planet region: they are typically defined as having a perihelion distance between 5.2 and 30 au, and a semi-major axis below 30 au (Jewitt 2009). In the best case scenarios, it could be sustained for as much as tens to hundreds of thousand years These findings imply that if crystallization is the driver for centaur activity, these centaurs should have suffered from a recent orbital change. – their perihelion distance q must be between 5.2 and 30 au; – their semi-major axis a must be below 30 au; – they must not be in a 1:1 long-term, stable, mean-motion resonance with a planet (i.e. we exclude in particular Jupiter and Neptune Trojans) Using these constraints in the JPL small-body database search engine yields a total of 226 inactive objects and 31 active objects. We note that two of these objects were not tracked (suffix nt in Table 1), and have 1 https://ssd.jpl.nasa.gov/sbdb_query.cgi A102, page 2 of 7 eccentricity

K15G53Y 7 o5p002nt 8 K15H09P 9 K15G54B 10 K15G54A

Findings

Discussion

Conclusion