Interstellar comets provide rare opportunities for probing the diversity of refractory and volatile inventory around other stars. As the second ever interstellar comet, and the third interstellar object, 3I/ATLAS has been the focus of telescopic observations since its discovery in July 2025. Following the previous observations at multi-wavelengths, we present further radio observations of the 1665/1667 MHz ground-state OH lines and millimeter observations of the CO($J$=1-0) transition at 115.271 GHz that trace the coma $\rm H_2O$ and CO abundances, respectively. We derived OH production rates of $(1.32\pm0.47)\times10^{28}\ \rm s^{-1}$ at 2.27 au and $(1.89\pm0.37)\times10^{28}\ \rm s^{-1}$ at 1.96 au as well as an average CO production rate of $\rm (5.75\pm1.91) \times 10^{27}\, s^{-1}$ between 2.33 and 1.75 au, inferring a CO/$\rm H_2O$ ratio of ($28\pm11\%$). With the mean HCN production rate of $2.5\times 10^{25}\ \rm s^{-1}$ at 2.1 au reported by \citet{2025arXiv251120845R} and \citet{2025arXiv251002817C}, we infer a CO/HCN ratio of ($230\pm76$). By synthesizing water production rates measured with instruments of different apertures, we found that the sublimation from extended source in the coma contributes significantly to 3I's pre-perihelion water measurements, accounting for up to 80\% from 3 au to 2 au.
SPHEREx Re-Observation of Interstellar Object 3I/ATLAS in December 2025: Detection of Increased Post-Perihelion Activity, Refractory Coma Dust, and New Coma Gas Species
Johns Hopkins University Applied Physics Laboratory（约翰斯·霍普金斯大学应用物理实验室）；Korea Astronomy and Space Science Institute（韩国天体宇宙科学研究所）；Arizona State University（亚利桑那州立大学）；California Institute of Technology（加州理工学院）；Jet Propulsion Lab（喷气推进实验室）；University of California Irvine（加州大学尔湾分校）；Infrared Processing and Analysis Center, Caltech（加州理工学院红外处理与分析中心）；Center for Astrophysics, Harvard & Smithsonian（哈佛-史密森尼天体物理中心）
Post-perihelion Coma Composition of the Interstellar Comet 3I/ATLAS from Optical Spectroscopy
CAS Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台光学天文重点实验室）；Yunnan Observatories, Chinese Academy of Sciences (CAS)（中国科学院云南天文台）；School of Astronomy and Space Sciences, University of Chinese Academy of Sciences（中国科学院大学天文学与空间科学学院）；Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales（迭戈帕托莱斯大学工程与科学学院天体物理研究所）；Planetary Science Institute（行星科学研究所）
Origin and evolution of NiI and FeI in the coma of the interstellar comet 3I/ATLAS throughout its trajectory
Université de Liège（列日大学）；University of Edinburgh（爱丁堡大学）；Université Catholique de Louvain（天主教鲁汶大学）；University of Canterbury（坎特伯雷大学）；Auburn University（奥本大学）；University of Helsinki（赫尔辛基大学）；University of Padova（帕多瓦大学）
研究揭示了镍和铁在星际彗星3I/ATLAS彗核 coma 中的起源与演化，发现其金属产量显著高于太阳系彗星，并提出羰基假说解释其形成机制。
Perihelion observations of interstellar comet 3I/ATLAS with the IRAM 30-m telescope
LIRA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, Université de Paris（巴黎天文台）；IRAM（红外毫米波天文台）；NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；Department of Physics, Catholic University of America（美利坚天主教大学物理系）；Department of Physics, American University（美利坚大学物理系）
Pre-perihelion Emergence of the CN Gas Coma in 3I/ATLAS Temporally and Spatially Resolved by the 7-Dimensional Telescope
Institute for Astronomy, University of Hawai‘i（夏威夷大学天体物理研究所）；Astronomy Program, Department of Physics and Astronomy, Seoul National University（首尔大学物理与天文学系天文项目）；SNU Astronomy Research Center, Seoul National University（首尔大学天文研究中心）；Korea Astronomy and Space Science Institute (KASI)（韩国天体宇宙科学研究所）
Comet 41P/Tuttle-Giacobini-Kresak (41P), a Jupiter family comet with three discoveries over about 100 years, is in a short-periodic orbit around the Sun with the perihelion close to the Earth distance. The 2017 apparition of 41P offered a long-lasting visibility of the comet at a close distance to Earth. The four month-long imaging campaign with the 2 m telescope at the Mount Wendelstein Observatory was aimed at characterizing dust activity and nucleus properties of the comet. Using a new analysis method of the inner coma flux, we derived a small mean equivalent radius of about 600 m for the n…
Pre-perihelion evolution of the NiI/FeI abundance ratio in the coma of the interstellar comet 3I/ATLAS. From extreme to normal
Université de Liège（列日大学）；University of Edinburgh（爱丁堡大学）；Pontificia Universidad Católica de Chile（智利天主教 Pontificia 大学）；University of Canterbury（坎特伯雷大学）；University of Helsinki（赫尔辛基大学）
Dust Activity Evolution and Constraints on Icy Grains in the Interstellar Comet 3I/ATLAS
State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology（澳门科技大学月球与行星科学国家重点实验室）；School of Aeronautics and Astronautics, Shenzhen Campus of Sun Yat-sen University（中山大学深圳校区航空航天学院）；Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）
The ESA Rosetta mission has allowed an extensive in-situ study of comet 67P/Churyumov-Gerasimenko. In measurements performed by the ram gauge of the on-board COmet Pressure Sensor (COPS), features have been observed that deviate from the nominal ram gauge signal. These are attributable to the sublimation of the volatile fraction of cometary icy particles containing volatiles and refractories. The objective of this work is the investigation of the volatile content of icy particles that entered the COPS ram gauge. The ram gauge measurements are inspected for features that we associate to the sub…
Mapping the release of volatiles in the inner comae of comets C/2012 F6 (Lemmon) and C/2012 S1 (ISON) using the Atacama Large Millimeter/Submillimeter Array
In an earlier study, we reported that the ram gauge of the COmet Pressure Sensor (COPS), one of the three instruments of the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA), could be used to obtain information about the sublimating content of icy particles, made up of volatiles and conceivably refractories coming from comet 67P/Churyumov-Gerasimenko. In this work, we extend the investigation to the second COPS gauge, the nude gauge. In particular, we analyse the volume of the volatile content of coma particles, along with a search for possible dependencies between the nude g…
There was an unprecedented opportunity to study the inner dust coma environment, where the dust and gas are not entirely decoupled, of comets 45P/Honda-Mrkos-Pajduusáková (45P/HMP) from Dec. 26, 2016 - Mar. 15, 2017, and 46P/Wirtanen from Nov. 10, 2018 - Feb. 13, 2019, both in visible wavelengths. The radial profile slopes of these comets were measured in the R and HB-BC filters most representative of dust, and deviations from a radially expanding coma were identified as significant. The azimuthally averaged radial profile slope of comet 45P/HMP gradually changes from -1.81 $\pm$ 0.20 at 5.24 …
We here study the transfer process of material from one hemisphere to the other (deposition of airfall material) on an active comet nucleus, specifically 67P/Churyumov-Gerasimenko. Our goals are to: 1) quantify the thickness of the airfall debris layers and how it depends on the location of the target area, 2) determine the amount of $\mathrm{H_2O}$ and $\mathrm{CO_2}$ ice that are lost from icy dust assemblages of different sizes during transfer through the coma, and 3) estimate the relative amount of vapor loss in airfall material after deposition in order to understand what locations are ex…
High-resolution optical spectroscopy reveals the distinctive volatile composition of the interstellar comet 3I/ATLAS
STAR Institute, Université de Liège（列日大学STAR研究所）；Institute for Astronomy, University of Edinburgh, Royal Observatory（爱丁堡大学天文研究所皇家天文台）；Physics Department, Edmund C. Leach Science Center, Auburn University（奥本大学艾德蒙·C·利奇科学中心物理系）；School of Physical and Chemical Sciences – Te Kura Matū, University of Canterbury（坎特伯雷大学物理与化学科学学院）；Faculty of Science and Engineering, Northumbria University（诺森比亚大学科学与工程学部）；Koyama Space Science Institute, Kyoto Sangyo University（京都产业大学小山宇宙科学研究所）；INAF – Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）
Dynamically New Comet C/2025 D1 (Groeller) with Record Perihelion Distance
Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；The University of Western Ontario（韦仕敦大学）；ESA NEO Coordination Centre, Planetary Defence Office（欧洲空间局近地天体协调中心行星防御办公室）
Hyperactive comets have high water production rates, with inferred sublimation areas of order the surface area of the nucleus. Comets 46P/Wirtanen and 103P/Hartley 2 are two examples of this cometary class. Based on observations of comet Hartley 2 by the Deep Impact spacecraft, hyperactivity appears to be caused by the ejection of water-ice grains and/or water-ice rich chunks of nucleus into the coma. These materials increase the sublimating surface area, and yield high water production rates. The historic close approach of comet Wirtanen to Earth in 2018 afforded an opportunity to test Hartle…
A Quarter-Century of Observations of Comet 10P/Tempel 2 at Lowell Observatory: Continued Spin-Down, Coma Morphology, Production Rates, and Numerical Modeling
Water Production of Interstellar Comet 3I/ATLAS from SOHO/SWAN Observations after Perihelion
University of Michigan（密歇根大学）；Finnish Meteorological Institute（芬兰气象局）；LATMOS/IPSL UVSQ Université Paris-Saclay, Sorbonne Université, CNRS（巴黎萨克雷大学、索邦大学、法国国家科学研究中心LATMOS/IPSL联合实验室）；ACRI-st；LIRA, Observatoire de Paris（巴黎天文台LIRA）
利用SOHO/SWAN观测，研究星际彗星3I/ATLAS水生产率，发现其在近日点后9天的水生产率为3.17 x 10^29 s^-1，随后逐渐下降。
Multi-Wavelength Post-Perihelion Polarimetry of Interstellar Comet 3I/ATLAS
University of Helsinki（赫尔辛基大学）；Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences（保加利亚科学院天文研究所与国家天文台）；Armagh Observatory & Planetarium（阿马天文台与天文馆）；University of Maryland（马里兰大学）；TU Braunschweig（布伦瑞克工业大学）；INAF – Osservatorio Astrofisico di Torino（意大利国家天体物理研究所都灵天文台）；Finnish Centre for Astronomy with ESO, University of Turku（图卢大学ESO芬兰天文学中心）；Luleå University of Technology（吕勒奥理工大学）
The Volatile Inventory of 3I/ATLAS as seen with JWST/MIRI
California Institute of Technology（加州理工学院）；Space Telescope Science Institute（太空望远镜科学研究所）；Eureka Scientific（尤里卡科学）；Auburn University（奥本大学）；Johns Hopkins University Applied Physics Laboratory（约翰斯·霍普金斯大学应用物理实验室）
The European Space Agency's Rosetta mission to comet 67P/Churyumov-Gerasimenko has offered scientists the opportunity to study a comet in unprecedented detail. Four instruments of the Rosetta orbiter, namely, the Micro-Imaging Dust Analysis System (MIDAS), the Grain Impact Analyzer and Dust Accumulator (GIADA), the COmetary Secondary Ion Mass Analyser (COSIMA), and the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) have provided information on cometary dust particles. Cross-instrument comparisons are crucial to characterize cometary dust particles beyond the capabilities of…
Coma Physics of an Interstellar Object: JWST Spatial-Spectral Mapping of 3I/ATLAS
NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；American University（美利坚大学）；The Catholic University of America（天主教大学）；Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris Cité（巴黎天文台、巴黎文理研究大学、法国国家科学研究中心、索邦大学、巴黎西岱大学）；LIRA（实验室天体物理学与红外研究）
We analyze jet features found in the coma of Comet 21P/Giacobini-Zinner (21P/GZ) during its 2018 perihelion passage using narrowband CN photometric imaging in order to determine the comet's rotational period, and constrain the CN gas outflow velocity and rotational state through the analysis of azimuthally enhanced morphological features. We find that 21P/GZ has a period of either 7.39 $\pm$ 0.01 or 10.66 $\pm$ 0.01 hours. We measure a lower limit to the outflow velocity for the Northern Jet of 730 $\pm$ 30 m s$^{-1}$ and for the Southern Jet of 740 $\pm$ 30 m s$^{-1}$. We analyze the morpholo…
In this work we aim to characterise the dust motion in the inner coma of comet 67P/Churyumov- Gerasimenko to provide constraints for theoretical 3D coma models. The OSIRIS camera onboard the Rosetta mission was able for the first time to acquire images of single dust particles from inside the cometary coma, very close to the nucleus. We analyse a large number of particles, performing a significant statistic of their behaviour during the post perihelion period, when the spacecraft covered distances from the nucleus ranging between 80 and 400 km. We describe the particle trajectories, investigat…
Contemporaneous Optical and Near-Infrared Observations of the Interstellar Comet 3I/ATLAS Pre- and Post-Perihelion
NSF Graduate Research Fellow（美国国家科学基金会研究生研究员）；Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales（迭戈帕托莱斯大学工程与科学学院天文研究所）；School of Earth and Atmospheric Sciences, Georgia Institute of Technology（佐治亚理工学院地球与大气科学学院）；Center for Cosmology and Astroparticle Physics, The Ohio State University（俄亥俄州立大学宇宙学与高能物理中心）
