Monica Lazzarin

Interstellar objects are the relics of planetary formation of extrasolar systems. They represent a unique opportunity to study insights of planetary formations around other stars. Since the discovery of 1I/‘Oumuamua in 2017, only two more interstellar objects have been found. 3I/ATLAS is the third, and its cometary nature was confirmed by early observations. Long‑slit spectra of comet 3I/ATLAS were obtained with the 1.22 m telescope at the Asiago Astrophysical Observatory. The 7' slit provided sufficient spatial coverage through the coma to investigate the release of atomic and molecular species. We provide the first extensive spatial‑distribution study of species in the coma of the interstellar comet 3I/ATLAS, with a total coverage of up to 2.8⋅ 10^5 km. Such spatial information has not previously been reported in the literature. We analysed the Fe I, Ni I, and CN emission features observed at 2.17 AU. We extracted the two‑dimensional long‑slit spectrum and performed the wavelength and flux calibration. From the resulting spectrum, we analysed the cometary emission line spatial distribution and the production rates of the parent molecules through a Haser modelling approach. Several neutral iron and nickel lines were detected together with the CN B-X (0-0) band. Production rates of CN and C_3 and 3σ NH upper limits were computed as well. We obtained the scale length of nickel, l_d(Ni) = 8.26 +2.12 _ -1.48 $ 10^5 km, and iron, l_d(Fe) = 2.48^ +0.57 _ -0.42 10^5 km. These results imply a slower outflow velocity with respect to Solar System comet values. The relative abundance was found: Ni/Fe = 0.20 ± 0.11. For CN, the obtained scale length is in agreement with typical values adopted for Solar System comets, but the CN parent scale length of l_p(CN) = 4.52^ +0.03 _ -0.03 10$^4 km we found is notably shorter than the usual values assumed or fitted for the CN parent in the literature. The iron and nickel scale lengths we computed suggest that they originate from a short‑lived parent, with no indication of an extended source in the coma. The lifetime of atoms are compatible with photoionisation under active Sun conditions. Our analysis of the CN spatial profile provides the first evidence that CN production in an interstellar comet may not follow the standard behaviour observed in Solar System comets. Our results indicate that CN in 3I likely originates from a combination of known parent molecules together with an additional short‑lived component or, alternatively, from a parent species with an outflow velocity significantly lower than typically inferred for Solar System comets.

We report spectropolarimetric and broadband polarimetric observations of the near-Earth asteroid (NEA) 2025 FA22 during its close approach on 18 September 2025 (about two Moon distances). With a diameter estimated between 130 and 290 m, 2025 FA22 is among the largest NEAs observable at such proximity, prompting an International Asteroid Warning Network (IAWN) rapid-response campaign. Although early orbital solutions indicated a possible impact in 2089, further follow-up astrometric observations ruled out a collision hazard. The favourable geometry of this close encounter enabled dense coverage of the positive part of the phase-polarisation curve, from the high polarisation domain (high phase angles), to near the inversion angle where the linear polarisation fraction vanishes. The spectropolarimetric observations provided the wavelength dependence of the polarisation fraction. Using empirical relationships, an estimate of the geometric albedo could be drawn from the slope of the phase-polarisation curve at an inversion angle p _v = 0.17 ± 0.04 in the V band. This value, together with the spectropolarimetric trend, provides constraints on the taxonomic class, with the results being most consistent with an M (or Xc)-type classification. These results demonstrate the value of polarimetry and spectropolarimetry for the rapid characterisation of newly discovered NEAs in planetary defence campaigns.

The study of cometary activity at large heliocentric distances provides insights into the volatile release processes in the outer solar system. Early models predicted cometary activity was driven primarily by sublimation of water and therefore would cease beyond the water snowline (2.5–3.5 au). However, observations have revealed several comets active well beyond this limit, suggesting the presence of additional mechanisms. The recently discovered Oort Cloud comet C/2024 E1 (Wierzchos) represents an opportunity to investigate the onset of distant activity in a dynamically new comet, a topic of particular relevance for ESA’s Comet Interceptor mission. We conducted visible spectroscopic monitoring of comet E1 with the Multi-Object Double Spectrographs at the Large Binocular Telescope to follow it from 6.3 to 3.3 au preperihelium. In this work, we report the first detection of CN emission, with the B – X (0–0) band observed as far as 4.05 au. We computed molecular production rates in the Haser coma model approximation. We found the onset of the CN radical B – X band as far as ∼4 au from the Sun. We report the following production rates: (5.50 ± 1.43) · 10 ²⁴ molec s ⁻¹ at 4.05 au; (6.77 ±1.43) · 10 ²⁴ molec s ⁻¹ at 3.82 au; and (4.25 ± 0.83) · 10 ²⁵ molec s ⁻¹ at 3.33 au. We measured upper limits on C ₂ and C ₃ at r _h = 3.3 au and found ratios with CN of log(Q C 2 /Q CN ) < −0.51 and log(Q C 3 /Q CN ) < −1.66. These values tentatively classify this comet as carbon-chain depleted.

We present spectroscopic observations of the third interstellar comet 3I/ATLAS obtained with the DOLORES instrument on the 3.58 m Telescopio Nazionale Galileo on 2025 August 16 ( r _h = 2.98 au). The spectrum revealed a red slope of 12.68% ± 0.05%/1000 Å across the 5000–8000 Å range, consistent with previous findings. Observations show the CN outgassing violet band, which yields a production rate of (4.28 ± 0.83) · 10 ²³ mol s ⁻¹ . We derived upper limits for C ₂ and C ₃ production rates since no clear detection was possible and used those to compute C ₂ /CN and C ₃ /CN ratios. The resulting, notably low, values of −0.86 and −1.47, respectively, for C ₂ /CN and C ₃ /CN ratios classify 3I as a strongly carbon-chain depleted comet in the preperihelion orbit. Notably, recent postperihelion observations found a typical solar system cometary composition, probably suggesting new innermost material being exposed to solar radiation.

On 26th September 2022, NASA’s Double Asteroid Redirection Test (DART) mission actively impacted the small moon Dimorphos of the Didymos-Dimorphos binary asteroid system. The impact caused a variation of about 33 minutes in its orbital period around Didymos and demonstrated the feasibility of moving an asteroid in space. As part of an international observing campaign devoted to its physical characterization, in this work we investigate the visible spectral properties of the Didymos-Dimorphos system soon after the impact. Rotationally-resolved spectra have been obtained 25 days after the impact and two months later. Geometric investigations have been performed to look for the source region corresponding to each spectrum. Here we show an overall agreement with pre-impact spectra and S-type classification despite subtle variations emerging, possibly correlated with mutual events. Furthermore a small long term color evolution from October to December spectra tentatively interpreted as related to dust cloud grain size effects or alternatively attributed to an uneven deposition of freshly exposed material from the impact on Didymos.

Kinetic deflection is a planetary defense technique delivering spacecraft momentum to a small body to deviate its course from Earth. The deflection efficiency depends on the impactor and target. Among them, the contribution of global curvature was poorly understood. The ejecta plume created by NASA’s Double Asteroid Redirection Test impact on its target asteroid, Dimorphos, exhibited an elliptical shape almost aligned along its north-south direction. Here, we identify that this elliptical ejecta plume resulted from the target’s curvature, reducing the momentum transfer to 44 ± 10% along the orbit track compared to an equivalent impact on a flat target. We also find lower kinetic deflection of impacts on smaller near-Earth objects due to higher curvature. A solution to mitigate low deflection efficiency is to apply multiple low-energy impactors rather than a single high-energy impactor. Rapid reconnaissance to acquire a target’s properties before deflection enables determining the proper locations and timing of impacts.

On 26 September 2022 Dimorphos, the small satellite of the Potentially Hazardous asteroid (PHA) Didymos, has been deviated from its orbit by the NASA DART spacecraft. On April 13, 2029, the Earth will witness one of the rarest events, never documented in such detail before: the asteroid Apophis will pass within 33,000 km of Earth.Apophis is a PHA that had raised great concern at its first discovery due to the not remote possibility that it could impact our planet in 2029. Like Didymos-Dimorphos and Apophis, among the Near Earth Asteroids (NEAs), there are many other PHAs, none of the known ones causing concern for possible impacts with our planet in the next decades, but which nonetheless need to be carefully monitored and studied to understand their physical and dynamic characteristics. With this spirit, since several years we have started a spectroscopic observational campaign of NEOs, particularly of PHAs.In this work we present an update of our spectroscopic survey of Near Earth Objects (NEOs), performed with the Asiago Telescopes. The program was also part of the EU-funded NEO Rapid Observation, Characterization and Key Simulations (NEOROCKS) project, focused on the acquisition and analysis of data on newly discovered small size objects, possibly PHAs.The importance of NEOs is widely recognized as they can help to investigate the origin and evolution of the Solar System, in particular also the origin of life and water on Earth, they are possible future mining resources, but they are also possible threatening objects to our planet. This is particularly true for the PHAs, the subgroup of NEOs characterized by orbits that can make close approaches to the Earth and large enough to cause significant regional damage in the event of an impact. Indeed, Didymos and Apophis are only two of the about 2400 PHA known so far. So it is particularly important and urgent to know in detail the dynamical, physical, and compositional properties of as many PHAs as possible in order also to have the necessary information to establish mitigation strategies. The encounter with the binary system Didymos-Dimorphos by the Hera mission in 2027 and of Apophis by the NASA/Osiris-Apex and hopefully by the ESA/Rames missions in 2029, will be unique opportunities to study with great detail these individual peculiar objects. Both missions will produce fundamental information useful to investigate the whole class of PHAs. At the same time, our ground-based investigation of PHAs will be extremely useful to better understand this class of objects as a whole and contribute to better interpret the huge quantity of data that will be obtained of Didymos-Dimorphos and of Apophis from ground and from space. They will be also used as a statistical reference for the whole class. Therefore, the study of PHAs enables the improvement of our planetary defence capabilities and the mitigation of the risks of impact with Earth. Our observations are performed with the 1.22m Galileo Telescope equipped with a Boller & Chivens spectrograph and the 1.82m Copernico Telescope equipped with AFOSC (Asiago Faint Object Spectrograph and Camera), located at the Asiago Observatory, Italy, covering a spectral range between 0.4 - 1 micron. The observations of PHAs are particularly challenging because of their typical faintness and their high speed rate . Nevertheless, since the beginning of the project, January 2020, we have observed about 70 NEOs of which 28 PHAs. Some of them are newly discovered, with a size ranging from 30 m to about 900 m. Most of them have an unknown taxonomic classification or not a clear one yet assigned. We performed the taxonomic classification through a comparison with spectral types from Bus-Binzel Taxonomy [1] and with laboratory meteorites spectra from the Relab database. Up to now we can account different types of asteroids, spanning from carbonaceous C to silicate S, and also some rare types as O or B. Some objects (eg, 1988 OR2 and Didymos) have been observed during their rotational periods, allowing the study of their surface variegation. We will present the results of the observational campaign obtained so far. Acknowledgments: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870403.References: [1] Bus & Binzel 2002, Icarus, 158, 146-177.

NASA's Double Asteroid Redirection Test (DART) mission was the first to demonstrate asteroid deflection, and the mission's Level 1 requirements guided its planetary defense investigations. Here, we summarize DART's achievement of those requirements. On 2022 September 26, the DART spacecraft impacted Dimorphos, the secondary member of the Didymos near-Earth asteroid binary system, demonstrating an autonomously navigated kinetic impact into an asteroid with limited prior knowledge for planetary defense. Months of subsequent Earth-based observations showed that the binary orbital period was changed by –33.24 minutes, with two independent analysis methods each reporting a 1σ uncertainty of 1.4 s. Dynamical models determined that the momentum enhancement factor, β, resulting from DART's kinetic impact test is between 2.4 and 4.9, depending on the mass of Dimorphos, which remains the largest source of uncertainty. Over five dozen telescopes across the globe and in space, along with the Light Italian CubeSat for Imaging of Asteroids, have contributed to DART's investigations. These combined investigations have addressed topics related to the ejecta, dynamics, impact event, and properties of both asteroids in the binary system. A year following DART's successful impact into Dimorphos, the mission has achieved its planetary defense requirements, although work to further understand DART's kinetic impact test and the Didymos system will continue. In particular, ESA's Hera mission is planned to perform extensive measurements in 2027 during its rendezvous with the Didymos–Dimorphos system, building on DART to advance our knowledge and continue the ongoing international collaboration for planetary defense.