  We have discovered two epochs of activity on quasi-Hilda 2009 DQ118. Small
bodies that display comet-like activity, such as active asteroids and active
quasi-Hildas, are important for understanding the distribution of water and
other volatiles throughout the solar system. Through our NASA Partner Citizen
Science project, Active Asteroids, volunteers classified archival images of
2009 DQ118 as displaying comet-like activity. By performing an in-depth
archival image search, we found over 20 images from UT 2016 March 8--9 with
clear signs of a comet-like tail. We then carried out follow-up observations of
2009 DQ118 using the 3.5 m Astrophysical Research Consortium Telescope at
Apache Point Observatory, Sunspot, New Mexico, USA and the 6.5 m Magellan Baade
Telescope at Las Campanas Observatory, Chile. These images revealed a second
epoch of activity associated with the UT 2023 April 22 perihelion passage of
2009 DQ118. We performed photometric analysis of the tail and find that it had
a similar apparent length and surface brightness during both epochs. We also
explored the orbital history and future of 2009 DQ118 through dynamical
simulations. These simulations show that 2009 DQ118 is currently a quasi-Hilda
and that it frequently experiences close encounters with Jupiter. We find that
2009 DQ118 is currently on the boundary between asteroidal and cometary orbits.
Additionally, it has likely been a Jupiter family comet or Centaur for much of
the past 10 kyr and will be in these same regions for the majority of the next
10 kyr. Since both detected epochs of activity occurred near perihelion, the
observed activity is consistent with sublimation of volatile ices. 2009 DQ118
is currently observable until ~mid-October 2023. Further observations would
help to characterize the observed activity.
