2009 DQ118

is an unnamed active asteroid located in the outer main asteroid belt. It was initially reported on 27 February 2009 by the Spacewatch survey at Steward Observatory in Tucson, Arizona, United States. Classified as a quasi-Hilda object, 's orbit is strongly perturbed by its frequent close encounters with Jupiter. It exhibits comet-like activity, which was first observed in March 2016 and identified by volunteers working for the Active Asteroids project. As of 2025, it has not received a number from the Minor Planet Center.

Orbit

orbits the Sun at an average distance—its semi-major axis—of 3.57 astronomical units, placing it in the outer main asteroid belt. Along its 6.75 year long orbit, its distance from the Sun varies between 2.43 AU at perihelion to 4.72 AU at aphelion due to its orbital eccentricity of 0.32. Its orbit is inclined by 9.39° with respect to the ecliptic plane.
is a member of a dynamical group of objects called the quasi-Hildas. The quasi-Hildas reside near, but do not participate in, the 2:3 mean-motion resonance with Jupiter. Unlike the Hilda asteroids, which are defined as participating in the 2:3 Jovian MMR, quasi-Hildas are dynamically unstable. experiences frequent close encounters with Jupiter, often coming as close as 2–3 Jupiter Hill radii to the planet.
, its Tisserand parameter with respect to Jupiter is 3.005, just above the T_J = 3 boundary. Objects with T_J < 3 are considered Jupiter-crossing comets, whereas those with T_J > 3 are considered asteroids. 's close encounters with Jupiter significantly alter its orbit, causing it to frequently cross the T_J = 3 boundary—up to dozens of times over the course of 1,000 years. Though currently in an asteroid-like orbit, in the past it was likely a Jupiter-family comet or a centaur. According to numerical simulations performed in 2023, it will once again become a JFC 1,000 years in the future. Thereafter, it is likely to remain a JFC or become a centaur, though there is a small chance that it will transition back to an asteroid-like orbit or even become a near-Earth object.

Activity

exhibits comet-like activity, which was first identified by citizen science volunteers working for the Active Asteroids project. Observations taken in 8–11 March 2016, four months before 's 2016 perihelion passage, showed a tail. Follow-up observations were conducted using the Apache Point Observatory's 3.5-m Astrophysical Research Consortium telescope on 24 February 2023. At that time, was approaching perihelion. Despite poor observing conditions, a faint tail was spotted, and further observations were carried out using Las Campanas Observatory's 6.5-m Walter Baade Magellan Telescope on 22 April, at 's perihelion. The 22 April observations also showed a faint tail. The timing of 's periods of activity with its perihelion passages suggests that its activity is likely driven by the sublimation of volatile ices.