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1. Cometary Activity Discovered on Vacationing Centaur 2019 OE31

   https://doi.org/10.3847/2515-5172/ad14f5  

   Oldroyd, William J.; Chandler, Colin Orion; Trujillo, Chadwick A.; Deen, Sam; Hsieh, Henry H.; Farrell, Kennedy A.; DeSpain, Jarod A.; Kueny, Jay K.; Burris, William A.; Sheppard, Scott S.; et al (December 2023, Research Notes of the AAS)

   Abstract We have detected cometary activity on minor planet 2019 OE₃₁through both theActive AsteroidsCitizen Science program and an independent archival search. Before 2013, 2019 OE₃₁was on a Centaur orbit, between the orbits of Jupiter and Neptune. Centaurs are objects in transition from the outer solar system to the inner solar system. They play a vital role in the understanding of the Kuiper Belt and comets. In 2013 October, following a close encounter with Jupiter, 2019 OE₃₁moved to an orbit entirely interior to that of Jupiter. This reduced orbital distance and, hence, increased temperature is likely the cause of the observed activity. Through a suite of orbital dynamics simulations, we find that 2019 OE₃₁will experience many more similar encounters and is statistically likely to return to a Centaur orbit, potentially within the next 80 yr, from its current “vacation.” 

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2. The Active Asteroids Citizen Science Program: Overview and First Results

   https://doi.org/10.3847/1538-3881/ad1de2  

   Chandler, Colin Orion; Trujillo, Chadwick A.; Oldroyd, William J.; Kueny, Jay K.; Burris, William A.; Hsieh, Henry H.; DeSpain, Jarod A.; Sedaghat, Nima; Sheppard, Scott S.; Farrell, Kennedy A.; et al (March 2024, The Astronomical Journal)

   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. 

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3. A Search of the Full Six Years of the Dark Energy Survey for Outer Solar System Objects

   https://doi.org/10.3847/1538-4365/ac3914  

   Bernardinelli, Pedro H.; Bernstein, Gary M.; Sako, Masao; Yanny, Brian; Aguena, M.; Allam, S.; Andrade-Oliveira, F.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; et al (February 2022, The Astrophysical Journal Supplement Series)

   Abstract We present a search for outer solar system objects in the 6 yr of data from the Dark Energy Survey (DES). The DES covered a contiguous 5000 deg 2 of the southern sky with ≈80,000 3 deg 2 exposures in the grizY filters between 2013 and 2019. This search yielded 812 trans-Neptunian objects (TNOs), one Centaur and one Oort cloud comet, 458 reported here for the first time. We present methodology that builds upon our previous search on the first 4 yr of data. All images were reprocessed with an optimized detection pipeline that leads to an average completeness gain of 0.47 mag per exposure, as well as improved transient catalog production and algorithms for linkage of detections into orbits. All objects were verified by visual inspection and by the “sub-threshold significance,” the signal-to-noise ratio in the stack of images in which its presence is indicated by the orbit, but no detection was reported. This yields a pure catalog complete to r ≈ 23.8 mag and distances 29 < d < 2500 au. The TNOs have minimum (median) of 7 (12) nights’ detections and arcs of 1.1 (4.2) yr, and will have grizY magnitudes available in a further publication. We present software for simulating our observational biases for comparisons of models to our detections. Initial inferences demonstrating the catalog’s statistical power are: the data are inconsistent with the CFEPS-L7 model for the classical Kuiper Belt; the 16 “extreme” TNOs ( a > 150 au, q > 30 au) are consistent with the null hypothesis of azimuthal isotropy; and nonresonant TNOs with q > 38 au, a > 50 au show a significant tendency to be sunward of major mean-motion resonances. 

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4. The DECam Ecliptic Exploration Project (DEEP). VI. First Multiyear Observations of Trans-Neptunian Objects

   https://doi.org/10.3847/1538-3881/ad1524  

   Smotherman, Hayden; Bernardinelli, Pedro H.; Portillo, Stephen K. N.; Connolly, Andrew J.; Kalmbach, J. Bryce; Stetzler, Steven; Jurić, Mario; Bektešević, Dino; Langford, Zachary; Adams, Fred C.; et al (February 2024, The Astronomical Journal)

   Abstract We present the first set of trans-Neptunian objects (TNOs) observed on multiple nights in data taken from the DECam Ecliptic Exploration Project. Of these 110 TNOs, 105 do not coincide with previously known TNOs and appear to be new discoveries. Each individual detection for our objects resulted from a digital tracking search at TNO rates of motion, using two-to-four-hour exposure sets, and the detections were subsequently linked across multiple observing seasons. This procedure allows us to find objects with magnitudesm_VR≈ 26. The object discovery processing also included a comprehensive population of objects injected into the images, with a recovery and linking rate of at least 94%. The final orbits were obtained using a specialized orbit-fitting procedure that accounts for the positional errors derived from the digital tracking procedure. Our results include robust orbits and magnitudes for classical TNOs with absolute magnitudesH∼ 10, as well as a dynamically detached object found at 76 au (semimajor axisa≈ 77 au). We find a disagreement between our population of classical TNOs and the CFEPS-L7 three-component model for the Kuiper Belt. 

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5. OSSOS. XXVI. On the Lack of Catastrophic Collisions in the Present Kuiper Belt

   https://doi.org/10.3847/1538-3881/ac9cdb  

   Abedin, Abedin Y.; Kavelaars, J. J.; Petit, Jean-Marc; Gladman, Brett; Bannister, Michele; Alexandersen, Mike; Chen, Ying-Tung; Gwyn, Stephen; Volk, Kathryn (November 2022, The Astronomical Journal)

   Abstract We investigate different conditions, including the orbital and size–frequency distribution (SFD) of the early Kuiper Belt, that can trigger catastrophic planetesimal destruction. The goal of this study is to test if there is evidence for collisional grinding in the Kuiper Belt that has occurred since its formation. This analysis has important implications for whether the present-day SFD of the cold classical trans-Neptunian objects (TNOs) is a result of collisional equilibrium or if it reflects the primordial stage of planetesimal accretion. As an input to our modeling, we use the most up-to-date debiased OSSOS++ ensemble sample of the TNO population and orbital model based on the present-day architecture of the Kuiper Belt. We calculate the specific impact energies between impactor–target pairs from different TNO groups and compare our computed energies to catastrophic disruption results from smoothed particle hydrodynamics simulations. We explore different scenarios by considering different total primordial Kuiper Belt masses and power slopes of the SFD and allowing collisions to take place over different timescales. The collisional evolution of the Kuiper Belt is a strong function of the unknown initial mass in the trans-Neptunian region, where collisional grinding of planetesimals requires a total primordial Kuiper Belt mass of M > 5 M ⊕ , collision speeds as high as 3 km s −1 , and collisions over at least 0.5 Gyr. We conclude that presently, most of the collisions in the trans-Neptunian region are in the cratering rather than disruption regime. Given the low collision rates among the cold classical Kuiper Belt objects, their SFD most likely represents the primordial planetesimal accretion. 

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