A Manx is a minor body on a long-period comet orbit that is inactive or minimally active at small perihelion distances (where water would be expected to be strongly sublimating), resulting in the lack of a significant tail. These objects are being discovered at a rate of about a dozen per year from large all-sky surveys, and the Pan-STARRS1 telescope in Hawai'i is the most prolific at discovering these weakly active objects. Manxes are theorized to be planetesimals that formed in the inner solar system, perhaps some even in the Earth-forming region, that were subsequently ejected out into the Oort cloud due to the migration of Jupiter and Saturn as the Solar System evolved. We use spectral reflectivities obtained with the Gemini North 8m telescope and ESO's Very Large Telescope to determine the surface composition of these objects. The observed Manxes exhibit a wide variety of surface properties, from primitive materials (i.e. C-, P- or D-types) to anhydrous materials (i.e. S-types). The relative numbers of objects with surface materials that are consistent with relatively dry, rocky inner solar system material may be used to constrain dynamical solar system formation models which make different predictions about the amount and sources of material that gets ejected to the Oort cloud. To date, we have observed 27 Manxes from 2013-2017. Here, we present preliminary results from this survey of spectral reflectivities for various Manxes. In addition, for some of the objects, we have sufficient heliocentric photometry to model the activity in terms of water-ice sublimation and can obtain estimates of the amount of near-surface water in comparison to comets. This work is supported in part by an NSF award AST-1617015, and is based in part on observations obtained at the Gemini Observatory acquired through the Gemini Observatory Archive (GN2015A-FT18, GN2016A-Q15, GN2016A-FT22, GN2016B-Q19, GN-2016B-FT-24, GN-2017A-Q-14) and the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 098.C-0303 and 099.C-0787.
AAS/Division for Planetary Sciences Meeting Abstracts #49
- Pub Date:
- October 2017