2009 DQ118

Active main belt asteroid November 2025 yes 2009 DQ 118 #D6D6D6 Discoverer not yet assigned by the MPC 27 February 2009 (Initial reported obs.) 2009 DQ 118 Outer main belt 21 November 2025 (JD 2461000.5) 0 2.4288 AU 4.7164 AU 3.5726 AU 0.3202 9.3931° 252.059° 344.652° 137.783° 6.7527 y (2466.4 d) 0.1460° / d 0.8036 AU 3.005 16.96 2009 DQ 118 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, 2009 DQ 118's orbit is strongly perturbed by 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 thumb|left|Diagram of 2009 DQ 118's orbit in the outer main belt, near the orbit of Jupiter. 2009 DQ 118 orbits the Sun at an average distance—its semi-major axis—of 3.57 astronomical units (AU), 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. 2009 DQ 118 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 (MMR) with Jupiter. Unlike the Hilda asteroids, which are defined as participating in the 2:3 Jovian MMR, quasi-Hildas are dynamically unstable.1 2009 DQ 118 experiences frequent close encounters with Jupiter, often coming as close as 2–3 Jupiter Hill radii (0.68–1.02 AU)rH,J ≈ 0.34 AU3 to the planet.3 2025, its Tisserand parameter with respect to Jupiter (TJ) is 3.005, just above the TJ = 3 boundary used by astronomers to distinguish Jupiter-crossing comets and asteroids.4 Objects with TJ < 3 are considered Jupiter-crossing comets, whereas those with TJ > 3 are considered asteroids.3 2009 DQ 118's close encounters with Jupiter significantly alter its orbit, causing it to frequently cross the TJ = 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 (JFC) 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.4 Activity 2009 DQ 118 shows 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 2009 DQ 118's 2016 perihelion passage, showed a tail. Follow-up observations were conducted using the Apache Point Observatory's 3.5-m Astrophysical Research Consortium (ARC) telescope on 24 February 2023. At that time, 2009 DQ 118 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 2009 DQ 118's perihelion. The 22 April observations also showed a faint tail.2 The timing of 2009 DQ 118's periods of activity with its perihelion passages suggests that its activity is likely driven by the sublimation of volatile ices.614 See also Other active asteroids identified by the Active Asteroids project: 6478 Gault (62412) 2000 SY 178 (323137) 2003 BM 80 Notes References 2009 DQ118 https://www.minorplanetcenter.net/db_search/show_object?object_id=2009+DQ118 Minor Planet Center 9 November 2025 live (38 obs) 2022-02-09 last obs. JPL Small-Body Database Lookup: (2009 DQ118) https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=2009%20DQ118 Jet Propulsion Laboratory 9 November 2025 live Oldroyd William J. et al. Recurring Activity Discovered on Quasi-Hilda 2009 DQ118 November 2023 The Astrophysical Journal Letters 957 1 L1 10.3847/2041-8213/acfcbc free 2311.02160 2023ApJ...957L...1O Chandler Colin Orion et al. The Active Asteroids Citizen Science Program: Overview and First Results April 2024 The Astronomical Journal 167 4 156 10.3847/1538-3881/ad1de2 free 2403.09768 2024AJ....167..156C The quasi-Hilda subgroup of ecliptic comets - an update Toth I. Astronomy and Astrophysics 448 3 1191–1196 March 2006 10.1051/0004-6361:20053492 2006A&A...448.1191T free External links 2009 DQ118 Astronomy Outer Space # 20090227 Category:Minor planet object articles (unnumbered)