Search for signatures of dust in the Pluto–Charon system using Herschel/PACS observations^⋆,⋆⋆

¹ Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Konkoly Thege Miklós út 15-17, 1121 Budapest, Hungary
e-mail: marton.gabor@csfk.mta.hu
² Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
³ Observatoire de Paris, CNRS, UPMC Univ. Paris 06, Univ. Paris-Diderot, 5 place Jules Janssen, 92195 Meudon Principal Cedex, France

Received: 15 January 2015
Accepted: 25 June 2015

Abstract

In this letter we explore the environment of Pluto and Charon in the far infrared with the main aim of identifying the signs of any possible dust ring, should it exist in the system. Our study is based on observations performed at 70 μm with the PACS instrument onboard the Herschel Space Observatory at nine epochs between March 14 and 19, 2012. The far-infrared images of the Pluto–Charon system are compared to those of the point spread function (PSF) reference quasar 3C 454.3. The deviation between the observed Pluto–Charon and reference PSFs are less then 1σ, indicating that clear evidence for an extended dust ring around the system was not found. Our method is capable of detecting a hypothetical ring with a total flux of ~3.3 mJy at a distance of ~153 000 km (~8.2 Pluto–Charon distances) from the system’s barycentre. We place upper limits on the total disk mass and on the column density in a reasonable disk configuration and analyse the hazard during the flyby of NASA’s New Horizons in July 2015. This realistic model configuration predicts a column density of 8.7 × 10^-10 g cm^-2 along the path of the probe and an impactor mass of 8.7 × 10^-5 g.