TNO or Comet? The Search for Activity and Characterization of Distant Object 418993 (2009 MS9)

Abstract The perihelion of the trans-Neptunian object (TNO) 2009 MS9 brings it close to distance where some long-period comets are seen become active. Knowing this, and fact that this appears brighten in excess its predicted nucleus brightness, suggests has a delayed onset activity brought on by sublimation species more volatile than water. In paper, we characterize MS9's physical properties investigate potential outgassing through composite images, models, measurements spectral reflectivity. We find deep images at various epochs along orbit show no evidence dust yet place sensitive limits production. estimate radius be 11.5 ± 3.5 km using thermal IR modeling from NEOWISE data use pre-perihelion geometric albedo 0.25. compare CO model post-perihelion heliocentric light curve these support an active fractional area 5 × 10 ?6 assuming 2 ? m–sized grains other typical comet parameters. reflectivity surface materials obtained with Gemini Observatory CFHT different shows reddening slope. both TNO populations speculate may due buildup mantle could explanation why TNOs exhibit color bimodality.