Abstract
We present the discovery of a short, diffuse tail on minor planet 2010 MK43 (alternate designation 2010 RA78)—an object previously identified as an asteroid in a cometary orbit—by volunteers of our Citizen Science program Active Asteroids. Our follow-up investigation revealed eight Dark Energy Camera images showing 2010 MK43 with a tail spanning UT 2024 February 12–UT 2024 February 18 when the object was outbound from perihelion. We now classify 2010 MK43 as a Jupiter-family comet based on its Tisserand parameter with respect to Jupiter TJ = 2.888, though our dynamical simulations reveal that, due to frequent close encounters with Jupiter, 2010 MK43 was likely a quasi-Hilda within the last 10 kyr.
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1. Introduction
Asteroids on Cometary Orbits (ACOs) are inactive minor planets with comet-like orbits that are typically subjected to strong gravitational influences by Jupiter (J. Licandro et al. 2006). Studies on albedos for these rare objects support the hypothesis that a significant fraction of this dynamical group is comprised of dead or dormant comets (Y. Kim et al. 2014; J. Licandro et al. 2016). Jupiter-family comets (JFCs) are objects with orbits similar to ACOs, but with the distinction that they have been observed to be active. More specifically, active or inactive objects must have a Tisserand parameter with respect to Jupiter 2 < TJ < 3 to be categorized under the A. Carusi et al. (1985) and H. F. Levison & M. J. Duncan (1994) definitions of a JFC or ACO, respectively. JFCs likely originated from the Kuiper Belt (S. Vaghi 1973; H. F. Levison 1996) and thus hold a primitive composition, including volatiles that may offer clues about the early evolution of the solar system and water delivery to the terrestrial planets.
2. Methods
Active Asteroids 18 (C. O. Chandler et al. 2024) is a Citizen Science and NASA partner program that we developed to perform an extensive search campaign in the public archive of the Dark Energy Camera (DECam) survey images for previously unknown active minor planets. Given the large volume of image data to sift through, we first identify and cut out thumbnail images of known minor planets which are then screened by our simple convolutional neural network, TailNet, to reject images that are unlikely to show an active object. By pre-filtering these thumbnails before delivering them to the Active Asteroids program, volunteers experience a streamlined workflow as they classify each thumbnail as "active" (i.e., they see a tail or coma) or not. We flag objects that get assigned promising activity scores for follow-up telescope observations, archival image searches, and dynamical simulations.
3. Results
Active Asteroids volunteers discovered dispersed dust emission, in the form of a comet tail, originating from 2010 MK43 (semimajor axis a = 3.49 au, eccentricity e = 0.458, inclination i = 16
6, perihelion distance q = 1.89 au, aphelion distance Q = 5.081 au) in DECam images (Figure 1). The object was imaged when it was outbound from perihelion on UT 2024 February 12 (true anomaly f = 24°) and UT 2024 February 18 (f = 27°). With the discovery of activity, and since 2010 MK43 has a Tisserand Parameter with respect to Jupiter TJ = 2.88, we classify 2010 MK43 as a JFC. From our dynamical analysis, we found 2010 MK43 experiences close encounters with Jupiter every few decades. These encounters destabilize the orbit of 2010 MK43 causing it to migrate to neighboring orbital regimes. We find that there is an ∼80% probability that its orbit will evolve to that of a Centaur or more distant object within the next 100 kyr. Additionally, for much of the last 40 kyr, 2010 MK43 orbited near the 3:2 mean-motion resonance with Jupiter and, hence, would have been a quasi-Hilda during this time period.
Figure 1. 2010 MK43 (center) in these r-band DECam images. The FOV is 63'' × 63'', with North up and East left; anti-motion (yellow arrow) and anti-solar (red-outlined black arrow) directions are shown. All images acquired with DECam on the 4 m Blanco telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile as part of Prop. ID 2024A-755342, PI Shen. Each image shown is a co-addition of 1 × 175 s g-band + 1 × 150 s g-band + 1 × 200 s i-band. In both images a short, diffuse tail is clearly visible oriented toward roughly 11 o'clock. (a) UT 2024 February 12 (observer M. Verrico). (b) UT 2024 February 18 (observer Kevin Luhman).
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Acknowledgments
Many thanks to Arthur and Jeanie Chandler for their ongoing support.
We thank Elizabeth Baeten (Belgium) for moderating the Active Asteroids forums. We thank our NASA Citizen Scientists who examined 2010 MK43: Al Lamperti (Royersford, USA), Antonio Pasqua (Catanzaro, Italy), C. S. Tolliver (Tucson, USA), Jan Jungmann (Chyňava, Czech Republic), Kelly Kramer (Colorado Springs, USA), Michele T. Mazzucato (Florence, Italy), Milton K. D. Bosch MD (Napa, USA), Pietro Maiorana (Palermo, Italy), Robert Zach Moseley (Worcester, USA), Rolf Erik Arndt (Buenos Aires, Argentina), Sergey Y. Tumanov (Glazov, Russia), Tania Betsaida Vázquez Rangel (Zapopan, Mexico), Tiffany Shaw-Diaz (Dayton, USA), and Yufan Fane Zhou (Nanjing, China). Additional thanks to Stacy L. Walker-Nez (Greasewood Springs, USA).
A special thanks to the Active Asteroids Superclassifiers: Angelina A. Reese (Sequim, USA), Antonio Pasqua (Catanzaro, Italy), Carl L. King (Ithaca, USA), Dan Crowson (Dardenne Prairie, USA), @EEZuidema (Driezum, Netherlands), Eric Fabrigat (Velaux, France), @graham_d (Hemel Hempstead, UK), Henryk Krawczyk (Czeladż Poland), Marvin W. Huddleston (Mesquite, USA), Robert Zach Moseley (Worcester, USA), Thorsten Eschweiler (Übach-Palenberg, Germany), and Washington Kryzanowski (Montevideo, Uruguay). Thanks to Cliff Johnson (Zooniverse), Chris Lintott (Oxford), Aprajita Verma (Oxford), and Marc Kuchner (NASA) for ongoing Citizen Science guidance.
This material is based upon work supported by the NSF Graduate Research Fellowship Program under grant No. 2018258765 and grant No. 2020303693. C.O.C., H.H.H., and C.A.T. acknowledge support from the NASA Solar System Observations program (grant 80NSSC19K0869). W.J.O. acknowledges support from NASA grant 80NSSC21K0114. This work was supported in part by NSF award 1950901. This research received support through Schmidt Sciences. Chandler and Sedaghat acknowledge support from the DiRAC Institute in the Department of Astronomy at the University of Washington. The DiRAC Institute is supported through generous gifts from the Charles and Lisa Simonyi Fund for Arts and Sciences, and the Washington Research Foundation.
Computational analyses were run on Northern Arizona University's Monsoon computing cluster, funded by Arizona's Technology and Research Initiative Fund.
This project used data obtained with the Dark Energy Camera (DECam), which was constructed by the Dark Energy Survey (DES) collaboration. This research uses services or data provided by the Astro Data Archive at NSF's NOIRLab. Based on observations at Cerro Tololo Inter-American Observatory, NSF's NOIRLab (NOIRLab Prop. ID 2014B-0404, PI: D. Schlegel; Prop. ID 2019A-0305, PI Drlica-Wagner).
Facility: CTIO:4m (DECam) - .
Software: astropy (T. P. Robitaille et al. 2013), astrometry.net (D. Lang et al. 2010), JPL Horizons (J. D. Giorgini et al. 1996), SkyBot (J. Berthier et al. 2006).