Upcoming and ongoing mutual events of trans-Neptunian binaries

The population of bodies beyond Neptune—generally called trans-Neptunian Objects (TNOs)—are critical to our understanding of the solar system. As leftover debris from planet formation, their orbital and physical characteristics inform our knowledge of the earliest moments of the solar system. Imprinted onto the orbital characteristics of the TNOs are signatures of planet migration and disturbances from stars in the Sun's birth cluster. Similarly, the physical characteristics of TNOs encode information about the composition of the protoplanetary disk, the conditions during planet formation, and the processes which enabled planetesimal formation. Unfortunately, physical characteristics of TNOs are difficult to probe given their extreme distances and small sizes. Thankfully, the abundant population of TNO binaries (TNBs) allow detailed physical characterization to be accomplished. 

One of the best times to characterize a TNB is during its mutual event season. Twice during each TNB’s heliocentric orbit, its binary mutual orbit appears edge-on (as seen from Earth) allowing for a series of occultations/eclipses between the binary components. Observing these events allows for detailed characterization of each components’ size, albedo, surface features, and even their surface thermal properties. Although this technique was used to great success for Pluto and Charon, limited success in observing and/or interpreting mutual events of TNBs has been had in the past two decades.

In this presentation, we will describe our threefold approach to improving the prediction of TNB mutual events. First, using the Hubble Space Telescope, we have observed 4 TNBs with upcoming/ongoing mutual event seasons. Second, we use precise ephemerides from the “Beyond Point Masses” project, which includes non-Keplerian precession into TNB orbital models. Third, we aim to provide well-characterized event predictions in a Bayesian framework that accounts for all sources of uncertainty in event predictions. With this approach, we will present updated predictions for the ongoing/upcoming mutual events of several TNBs.