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Abstract MagAO-X is a recently commissioned extreme adaptive optics instrument for the Magellan Clay 6.5 m telescope at Las Campanas Observatory in Chile. MagAO-X had first light in 2019 and subsequent commissioning observations in 2022 and 2023. An essential step for the commissioning of any new instrument is the calibration of the conversion of detector coordinates to angular sky coordinates, which we accomplish with observations of HD 165054. The background stars adjacent to HD 165054 in Baade’s Window are in a fortuitous configuration for the astrometric calibration of natural-guide-star high-contrast imaging instruments. We extend past work to connect these stars’ positions to absolute astrometry for HD 165054 itself using Gaia Data Release 3 data, and bootstrap the creation of an astrometric solution for our new high-contrast imaging instrument. Through Markov Chain Monte Carlo analysis of the historical data and position measurements from MagAO-X, we obtain updated astrometric parameters for the seven background stars and an astrometric calibration of the MagAO-X science cameras. 

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 programActive Asteroids. Our follow-up investigation revealed eight Dark Energy Camera images showing 2010 MK₄₃with a tail spanning UT 2024 February 12–UT 2024 February 18 when the object was outbound from perihelion. We now classify 2010 MK₄₃as a Jupiter-family comet based on its Tisserand parameter with respect to JupiterT_J = 2.888, though our dynamical simulations reveal that, due to frequent close encounters with Jupiter, 2010 MK₄₃was likely a quasi-Hilda within the last 10 kyr. 

Abstract We report the discovery of cometary activity emanating from minor planet 2015 VP₅₁outbound from its recent perihelion passage. The activity, in the form of a diffuse tail, was first identified by volunteers of our Citizen Science programActive Asteroids, a NASA Partner program hosted on theZooniverseplatform. This discovery was aided by the recently implementedTailNetartificial intelligence assistant which filters out images with a low likelihood of showing cometary activity. The tail is present in nine images of 2015 VP₅₁from the Dark Energy Camera and OmegaCAM between UT 2015 August 2 and UT 2015 October 18. We classify 2015 VP₅₁as a Jupiter-family comet based on its Tisserand parameter with respect to JupiterT_J = 2.931.