Active Quasi-Hilda 2009 DQ118 and the Asteroid-Comet Boundary

Comet-like activity, such as a tail or coma, is an indicator of changing conditions on small bodies in the solar system. To study these changes, we developed the Active Asteroids Citizen Science Project, a NASA Partner, hosted on the Zooniverse platform. Through this program, volunteers have made millions of classifications of images of solar system minor planets in search of comet-like features. As a result of this work, we discovered activity emanating from asteroid 2009 DQ118. Dynamical analysis of 2009 DQ118 reveals that it is a quasi-Hilda object, i.e., it is near, but not in, the interior 3:2 mean-motion resonance with Jupiter. Additionally, 2009 DQ118 has a Tisserand parameter with respect to Jupiter of TJ = 3.004. This is directly on the boundary between objects with asteroidal orbits (TJ > 3) and objects with cometary orbits (TJ < 3). On a timescale of hundreds of years 2009 DQ118 has dozens of close encounters with Jupiter causing it to migrate across the TJ = 3 boundary several times. This blurring of the asteroid-comet boundary may be connected with the detection of activity on 2009 DQ118 and may also indicate a potential pathway for transition between these two populations.