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Abstract We report the discovery of recurrent activity on quasi-Hilda comet (QHC) 362P/(457175) 2008 GO₉₈. The first activity epoch was discovered during the perihelion passage of 362P in 2016, so we were motivated to observe it for recurrent cometary activity near its next perihelion passage (UT 2024 July 20). We obtained observations with the Lowell Discovery Telescope, the Astrophysical Research Consortium telescope, and the Vatican Advanced Technology Telescope and identified a second activity epoch when 362P had a true anomaly (ν) as early as 318 $\stackrel{\text{°}}{.}$1. We conducted archival searches of six repositories and identified images obtained with Canada–France–Hawaii Telescope MegaCam, Dark Energy Camera, Pan-STARRS 1, SkyMapper, Zwicky Transient Facility, and Las Cumbres Observatory Global Telescope network data. Using these data, we identified activity from a previously unreported time span, and we did not detect activity when 362P was away from perihelion, specifically 83^∘<ν< 318^∘. Detection of activity near perihelion and absence of activity away from perihelion suggest thermally driven activity and volatile sublimation. Our dynamical simulations suggest 362P is a QHC, and it will remain in a combined Jupiter-family comet (JFC) and quasi-Hilda orbit over the next 1 kyr though it will become increasingly chaotic nearing the end of this timeframe. Our reverse simulations suggest 362P may have migrated from the orbit of a long-period comet (∼53%) or Centaur (∼32%); otherwise it remained a JFC (∼15%) over the previous 100 kyr. We recommend additional telescope observations from the community as 362P continues outbound from its perihelion on UT 2024 July 20, as well as continued observations for a third activity epoch. 

Abstract We report the discovery of cometary activity in the form of a pronounced tail emanating from Near-Earth Object (523822) 2012 DG₆₁, identified in UT 2024 April 18 Dark Energy Camera images by our AI assistant TailNet. TailNet is an AI designed to filter out images unlikely to show activity for volunteers of our NASA Partner “Active Asteroids” Citizen Science campaign, from which our AI is trained. Subsequently, our archival investigation revealed 2012 DG61 is recurrently active after we found it displaying a pronounced tail in a UT 2018 April 16 Steward Observatory Bart Bok 2.3 m telescope image and UT 2018 May 14 observations by G. Borisov with the 0.3 m telescope at MARGO Observatory. Our dynamical integrations reveal that 2012 DG61, an Apollo dynamical class member, is likely in 2:1 mean-motion resonance with Jupiter. We encourage additional observations to help characterize the activity morphology of this near-Earth comet. 

Abstract We report the discovery of cometary activity from minor planet 2011 UG₁₀₄, which we classify as a Jupiter Family Comet (JFC). This discovery was aided by our Artificial Intelligence (AI) classification system:TailNet. JFC's, short-period comets with eccentric Jupiter-crossing orbits, originate from the Kuiper Belt and thus give us unique insight into the composition and distribution of volatiles in the outer solar system, past and present. Our AI assistantTailNetfirst classified 2011 UG₁₀₄as active, which was affirmed by Citizen Scientists on our NASA Partner ProgramActive Asteroids. Through further archival image searches our science team found evidence of activity on 2011 UG₁₀₄on three separate observations from 2021 February to 2021 April (81.°8 < f < 95.°0).  

Abstract We report the discovery of an active asteroid, 2016 UU₁₂₁, for the first time via artificial intelligence-enhanced classification, informed by our NASA Partner programActive Asteroids, a Citizen Science project hosted on theZooniverseplatform. The early version of our deep neural network,TailNet, identified potential activity associated with 2016 UU₁₂₁in 40 Dark Energy Camera (DECam) images from UT 2021 September 10 to 11. The discovery was vetted and confirmed by ourActive Asteroidscore science team. In total, 66 DECam images of this object showed clear activity in the form of a tail. 2016 UU₁₂₁has a Tisserand parameter with respect to Jupiter of 3.161, thus we classify the object as an active asteroid. Moreover, the activity occurred near perihelion, so 2016 UU₁₂₁is also a candidate Main-belt comet. 

Abstract We report the discovery of cometary activity emanating from Main-belt asteroid 410590 (2008 GB₁₄₀), a finding facilitated, for the first time, by an artificial intelligence (AI) assistant. The assistant,TailNet, is a prototype we designed to enhance volunteer efforts of our Citizen Science projectActive Asteroids, a NASA Partner program hosted on theZooniverseplatform. Our follow-up investigation revealed eight Dark Energy Camera images showing 2008 GB₁₄₀with a tail spanning UT 2023 April 23–UT 2023 July 3, when the object was inbound to perihelion. We classify 2008 GB₁₄₀as an active asteroid and a candidate Main-belt comet (MBC)—a main-belt asteroid that undergoes volatile sublimation-driven activity. Notably, 2008 GB₁₄₀is presently near perihelion, thus the object is a prime target for follow-up observations to further characterize its activity. 

Abstract We present the Citizen Science program Active Asteroids and describe discoveries stemming from our ongoing project. Our NASA Partner program is hosted on the Zooniverse online platform and launched on 2021 August 31, with the goal of engaging the community in the search for active asteroids—asteroids with comet-like tails or comae. We also set out to identify other unusual active solar system objects, such as active Centaurs, active quasi-Hilda asteroids (QHAs), and Jupiter-family comets (JFCs). Active objects are rare in large part because they are difficult to identify, so we ask volunteers to assist us in searching for active bodies in our collection of millions of images of known minor planets. We produced these cutout images with our project pipeline that makes use of publicly available Dark Energy Camera data. Since the project launch, roughly 8300 volunteers have scrutinized some 430,000 images to great effect, which we describe in this work. In total, we have identified previously unknown activity on 15 asteroids, plus one Centaur, that were thought to be asteroidal (i.e., inactive). Of the asteroids, we classify four as active QHAs, seven as JFCs, and four as active asteroids, consisting of one main-belt comet (MBC) and three MBC candidates. We also include our findings concerning known active objects that our program facilitated, an unanticipated avenue of scientific discovery. These include discovering activity occurring during an orbital epoch for which objects were not known to be active, and the reclassification of objects based on our dynamical analyses. 

Abstract We present evidence that, on UT 2018 February 15, main-belt asteroid (588045) 2007 FZ₁₈displayed cometary activity in the form of two tails, one each in the anti-solar and anti-motion directions. Activity was first identified by volunteers of the NASA Partner program Active Asteroids, a Citizen Science program hosted on the Zooniverse platform, in an image acquired with the Dark Energy Camera on the Blanco 4 m telescope at the Cerro Tololo Inter-American Observatory in Chile. Notably, (588045) 2007 FZ₁₈is inbound toward perihelion, so telescope observations are timely to detect a possible second activity outburst. 

Abstract We announce the discovery of cometary activity emitting from minor planet 2018 VL₁₀in Dark Energy Camera images spanning from UT 2018 December 31 to UT 2019 March 3. The activity was identified by volunteers of our NASA Partner programActive Asteroids, aZooniverse-hosted Citizen Science project designed to find previously unknown activity in known minor planets. Notably, 2018 VL₁₀crosses the orbits of Mars and Jupiter, and experiences close approaches of less than 0.5 au with both Earth and Jupiter. We classify 2018 VL₁₀as a member of the Jupiter-family comets, a group of objects especially important to understand because they hold important clues about the solar system volatile distribution, past and present. 

Abstract We report our discovery of cometary activity in the form of a diffuse tail associated with minor planet 2008 QZ₄₄during two previous orbits: 2008 and 2017. This finding was prompted in part byActive Asteroids, ourZooniverse-hosted NASA Partner Citizen Science program. Participants flagged two UT 2017 July 12 Dark Energy Camera images of 2008 QZ₄₄as active. Independently, our team identified activity in nine Canada-France-Hawaii Telescope MegaPrime images from UT 2008 November 20. During both apparitions 2008 QZ₄₄was near its perihelion passage. 2008 QZ₄₄has a Tisserand parameter with respect to Jupiter of 2.821, placing it in the Jupiter-family comet (JFC) class, and our dynamical integrations confirm this classification. JFCs contain primordial material that informs us about solar system evolution, and help us map the present-day volatile distribution. We note that 2008 QZ₄₄has previously been classified as a quasi-Hilda comet candidate. 

Abstract We report the discovery of cometary activity associated with minor planet 2005 XR₁₃₂, a finding facilitated by our NASA Partner programActive Asteroids, hosted on the Zooniverse online Citizen Science platform. Volunteers identified activity in a Dark Energy Camera image of 2005 XR₁₃₂from UT 2021 March 26, and our own investigation uncovered additional images of activity in Zwicky Transient Facility data spanning UT 2021 January 3 through March 31. 2005 XR₁₃₂has a semimajor axisa = 3.760 au, eccentricitye= 0.432, inclinationi = 14.°474, and a Tisserand parameter with respect to Jupiter ofT_J= 2.869, and thus is dynamically classified as a Jupiter-family comet.