3- 1Lowell Observatory, Flagstaff AZ, United States of America (thirouin@lowell.edu)
- 2Carnegie Institution for Science, Earth & Planets Laboratory, Washington DC, United States of America (ssheppard@carnegiescience.edu)
- 3NASA - Goddard Space Flight Center (NASA-GSFC), Greenbelt MD, United States of America (keith.s.noll@nasa.gov)
A close/contact binary can be a small body with a bi-lobed shape, two objects touching at one point, and two objects with a small separation of less than a few hundred kilometers. Contact binaries are common in our Solar System's small body populations, as they are found in the near-Earth object, comet, main belt asteroid, and trans-Neptunian object populations.
Several models have been proposed to explain the formation of trans-Neptunian contact binaries, and we can cite for example: (1) a wide binary system can shrink its orbit and end up in a compact configuration due to dynamical effects, (2) binaries formed directly from gravitationally unstable clouds of much smaller particles through pebble accretion and if clumps are formed close enough they will end up as contact binaries, and (3) a physical collision between two objects can result in their accretion, within the sphere of influence of a third object
Unfortunately, none of these proposed models have been thoroughly tested with observations, as the contact binary trans-Neptunian population remained elusive until recently. Now that we have a sizeable sample of confirmed and likely contact binaries in the trans-Neptunian belt, we can test these models as they predict different outcomes regarding the presence of a widely separated moon orbiting the contact binary. If the first model based on dynamical effects is responsible for contact binary formation, no contact binary should have a moon if created from a two-body system. With three-body interactions, one has to expect many triple systems, whereas the gravitational collapse should give a mix of triple systems and contact binaries with no moon.
Using archival and new Hubble Space Telescope observations, we will present some preliminary results regarding the fraction of contact binaries with/without a moon and their distribution in several trans-Neptunian sub-populations.
This work is supported by HST-GO-17524 and the National Science Foundation grants #1734484 and #2109207.
How to cite: Thirouin, A., Sheppard, S. S., Grundy, W. M., and Noll, K. S.: Moon(s) around Contact Binary Trans-Neptunian Objects., EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–12 Sep 2025, EPSC-DPS2025-225, https://doi.org/10.5194/epsc-dps2025-225, 2025.
