Alan Fitzsimmons

We report observations of main-belt comet (MBC) 433P/(248370) 2005 QN ₁₇₃ using Las Cumbres Observatory 1 m telescopes in Australia and South Africa, Faulkes Telescope North, Faulkes Telescope South, the Astrophysical Research Consortium 3.5 m telescope, the New Technology Telescope, the Lowell Discovery Telescope, and Rubin Observatory from UT 2026 March 25 to UT 2026 July 26, where visible comet-like activity was observed from UT 2026 June 10 onwards, marking the object’s third confirmed active apparition. When active in the observations reported here, the object displays a narrow tapered tail up to 20″ long aligned with the antisolar direction. These observations mark 433P’s third confirmed active apparition, reinforcing its identification as a MBC.

We report observations of main-belt comet (MBC) 259P/Garradd (2008 R1) using Faulkes Telescope South, Las Cumbres Observatory 1 m telescopes in South Africa and Australia, and the European Southern Observatory’s New Technology Telescope from UT 2026 July 10 to UT 2026 July 17 showing visible comet-like activity, marking its third confirmed active apparition. In all observations reported here, the object displays a relatively narrow fan-shaped tail approximately 30″ long aligned with the antisolar direction. These observations mark 259P’s third confirmed active apparition, solidifying its identification as a MBC. We measure an average apparent r ′ -band magnitude of m _r ∼ 19.5 mag over the reported observing period.

Comets and Centaurs trace the evolution of trans-Neptunian objects (TNOs) into the inner solar system. Their activity reflects the interplay between volatile sublimation, dust dynamics, and, in some cases, ring scattering. Yet the long-term behavior of individual objects remains less constrained. To probe this evolutionary transition, we use wide-field survey photometry from the Asteroid Terrestrial-impact Last Alert System (ATLAS), Zwicky Transient Facility, and targeted Las Cumbres Observatory observations of the Jupiter-family comet (JFC) 103P/Hartley 2 during its 2023/24 apparition, and the Centaur (2060) Chiron across 2020–2025, including its 2021 outburst. For 103P, heliocentric activity slopes are asymmetric about perihelion, with a steep inbound index ( n r , pre = − 3.48 ± 0.08 ) and flatter outbound value ( n _{r ,post} = −1.16 ± 0.04), consistent with enhanced relative dust contribution postperihelion. With reduced brightness versus prior apparitions, this behavior matches reported secular fading trends. Dust mass-loss rates are ∼4–16 kg s ⁻¹ for assumed grain properties. Colors exhibit a blueward trend near perihelion, consistent with enhanced gas contamination of the g band, with possible phase-dependent scattering. Periodogram analysis recovers a ∼18.7 hr activity-linked period near perihelion. For Chiron, subtracting a quiescent baseline reveals exponential decay from the 2021 outburst on a ∼1.4 yr timescale. Seasonal phase curves flatten from β _o = 0.150 ± 0.034 mag deg ⁻¹ in 2021 to ≲0.09 mag deg ⁻¹ by 2023–2025, converging with quiescent behavior. Broadband colors remain unchanged at ATLAS ( c − o ) = 0.22 ± 0.09 mag. The extended duration of this activity suggests a new epoch of persistent, low-level activity and/or evolving ring scattering. These two objects bracket the TNO-to-JFC evolutionary sequence, with 103P near the volatile-depleted end, and Chiron still volatile-rich and capable of episodic activity.

The ESA Hera mission [1] is the European contribution to the first asteroid deflection test with the NASA DART mission. The DART probe successfully impacted Dimorphos, the small moon of the binary asteroid Didymos, on September 26, 2022. The orbital period modification of Dimorphos around Didymos, measured by ground-based observatories, was reduced by 33 minutes from its original value of 11h 55 min. The Italian LICIACube obtained some images of Dimorphos within the first few minutes following impact. However, we still do not know Dimorphos' final properties, modified by this impact, because no other spacecraft remained long enough in close proximity to collect such observations. Is there a crater on Dimorphos' surface, and if so, what are its properties? Or, was Dimorphos entirely reshaped? Answers to these questions are crucial for numerical simulations of the DART impact, required to reproduce these final properties to be validated as well as for our general understanding of the impact response of such objects in low-gravity regimes.Hera will, therefore, perform the investigation starting in November 2026 for at least 6 months. Although we already have images of Dimorphos before impact thanks to DART, we are confident that the images that Hera will take of the same body will have little similarity with those already obtained. This is because an impact with likely global effects took place. Furthermore, Didymos, the primary of the binary system may also look very different compared to pre-DART impact images. It is expected that some fraction of the ejecta from Dimorphos impacted Didymos, which may have modified its morphology and surface properties. Hera will, therefore, reveal an entirely new world, transformed by an event aimed at protecting us from an incoming asteroid, allowing us to assess the efficiency of the kinetic impactor technique. Thanks to its main spacecraft and its two cubesats, we will have detailed knowledge of the system, from the surface to the interior of the two components, including the composition and thermal properties through a spectrometer and a JAXA-contributed thermal infrared imager.So far, all newly obtained data of asteroids from previous missions have revealed some surprises [2]. Two months before arrival, we can expect Hera to also surprise us and challenge our understanding of these small worlds.Acknowledgments: The authors acknowledge support from ESA, ASI, CNES, DLR, JAXA, NASA.ReferencesMichel P., et al., Planetary Science Journal 2022, 3, 160-180.Michel P., et al., Space Science Reviews 2025, 221, 270.

The interstellar comet 2I/Borisov is the first interstellar object where compositional characterisation was possible throughout its entire perihelion passage. We report all 16 epochs of a comprehensive optical observation campaign with ESO Very Large Telescope’s integral field spectrograph MUSE, spanning 126 days from 2019 November 14 to 2020 March 19. The spatial dust emission of 2I/Borisov was predominantly smooth, with no seasonal effect. A jetlike feature was consistently visible. The gas production morphology of its coma was also smooth and similar for C ₂ , NH ₂ , and CN: symmetric around the optocentre. The production rates of these species gently declined into and beyond perihelion, until 2I’s outburst and splitting event in early 2020 March. C ₂ , NH ₂ , and CN production rates all increased, with NH ₂ being the most significant; the dust emission also slightly reddened. 2I/Borisov is a carbon-depleted, relatively NH ₂ -rich comet when compared to those comets yet measured in the solar system.

The Near‐Earth Object Mission in the Infrared (NEOMIR) is European Space Agency’s (ESA’s) space‐based mission dedicated to discovering near‐Earth objects (NEOs). Its primary goal is to detect and provide early warnings for NEOs approaching Earth approaching from the near‐Sun direction, which are nearly impossible to observe using ground‐based optical surveys. NEOMIR is currently in the early stages of mission study (Phase A), with a potential launch date in the early 2030s.

Current wide-field surveys discover ∼15 Jupiter-family comets (JFCs) each year, typically identified via visual detection of a dust coma or tail. The same surveys also discover many asteroids that have distant JFC-like orbits, but with no reported activity. We observed asteroids on Jupiter-crossing orbits beyond the depth of typical survey imaging using the 2.5 m Isaac Newton Telescope. We used deep imaging to observe 16 asteroids in this region, plus seven known comets for comparison. Three asteroids (2011 WM183, (669525) 2012 XO144, and 2020 RX133) showed surface brightness profiles consistent with low-level activity, equating to ∼19% of our total sample. We note that 2020 RX133 is a Jupiter Trojan. When we considered the heliocentric distance range of the asteroids at the time when they showed activity, this fraction increased to 33% of the targets in the 3.16 au ≤ R _h ≤ 4.56 au region, and therefore it is possible to infer that at least ∼30 asteroids with T _J ≤ 3.05 and in the 4.05 au < a < 5.05 au parameter space may potentially exhibit low-level activity. We also estimated nuclear radii for the three active targets of r _n = 1.8 ± 0.2 km, r _n ≤ 0.8 km, and r _n ≤ 0.5 km for (669525) 2012 XO144, 2011 WM183, and 2020 RX133, respectively. The median color index for the observed asteroids is ( g − r ) _PS1 = 0.52 ± 0.13, aligning with those expected for D-type asteroids.

We present calibrated Asteroid Terrestrial-impact Last Alert System (ATLAS) photometry of the interstellar comet 3I/ATLAS (C/2025 N1) from March 28 through 2025 August 29, obtained with the five-site, robotic ATLAS network in the c (420–650 nm), o (560–820 nm), and Teide w (420–720 nm) bands. Stacked difference images yield reliable light curves measured in four fixed apertures that capture the evolving coma. We observe 3I/ATLAS transitioning in color from red ( c − o ) ≈ 0.7 before MJD 60860 to near-solar ( c − o ) ≈ 0.3 after MJD 60870, coincident with the appearance of a prominent antisolar tail. The absolute magnitude curve H ( t ) shows a slope break near MJD 60890 at r ∼ 3.3 au from −0.035 to −0.012 mag day ⁻¹ , or in terms of coma cross section as a function of heliocentric distance, r ^−3.9 to r ^−1.1 . We release the aperture photometry with geometry and uncertainties to enable cross-instrument synthesis of 3I/ATLAS activity and color evolution.

The interstellar comet 2I/Borisov is the first interstellar object where compositional characterisation was possible throughout its entire perihelion passage. We report all 16 epochs of a comprehensive optical observation campaign with ESO VLT’s integral field spectrograph MUSE, spanning 126 days from 2019 November 14 to 2020 March 19. The spatial dust emission of 2I/Borisov was predominantly smooth, with no seasonal effect. A jet-like feature was consistently visible. The gas production morphology of its coma is also smooth and similar for C2, NH2, and CN: symmetric around the photocentre. The production rates of these species gently declined into and beyond perihelion, until 2I’s outburst and splitting event in early 2020 March. NH2 then significantly spiked, with a only moderate rise in C2 and CN; the dust emission also slightly reddened. 2I/Borisov is a carbon-depleted, very NH2-rich comet relative to those yet measured in the Solar System.