Related papers: Prediscovery Activity of New Interstellar Object 3…

Most Kreutz family sungrazing comets are discovered only days before perihelion, severely limiting observational opportunities to study their physical nature and decay. Kreutz sungrazer C/2024 S1 (ATLAS) was discovered a month before…

The first interstellar objects, 1I/`Oumuamua, 2I/Borisov and 3I/ATLAS, were discovered over the past decade. We follow the trajectories of known interstellar objects in the gravitational potential of the Milky Way galaxy to constrain their…

Comets are primitive objects that formed in the protoplanetary disk, and have been largely preserved over the history of the Solar System. However, they are not pristine, and surfaces of cometary nuclei do evolve. In order to understand the…

The atomic and molecular compounds of cometary ices serve as valuable knowledge into the chemical and physical properties of the outer solar nebula, where comets are formed. From the cometary atmospheres, the atoms and gas-phase molecules…

Comet 67P/Churyumov-Gerasimenko was selected in 2003 as the new target of the Rosetta mission. It has since been the subject of a detailed campaign of observations to characterise its nucleus and activity. Here we present previously…

Observations of comet 67P/Churyumov-Gerasimenko were performed with MUSE at large heliocentric distances post-perihelion, between March 3 and 7, 2016. Those observations were part of a simultaneous ground-based campaign aimed at providing…

Comet C/2006 W3 (Christensen) was observed in November 2009 at 3.3 AU from the Sun with Herschel. The PACS instrument acquired images of the dust coma in 70- and 160-micrometers filters, and spectra covering several H2O rotational lines.…

We use astrometric data on 3I/ATLAS compiled by the Minor Planet Center from May 15 to September 23, 2025, and derive an upper limit on any statistically significant deviation from the best-fit gravity-based trajectory. The residuals imply…

We present Hubble Space Telescope observations of a photometric outburst and splitting event in interstellar comet 2I/Borisov. The outburst, first reported with the comet outbound at 2.8 AU (Drahus et al.~2020), was caused by the expulsion…

We present the results of a molecular survey of long period comets C/2021 A1 (Leonard) and C/2022 E3 (ZTF). Comet C/2021 A1 was observed with the IRAM 30-m radio telescope in November-December 2021 before perihelion when it was closest to…

We present an observational and numerical study of the borderline hyperbolic comet C/2021 O3 (PANSTARRS) performed during its recent passage through the inner Solar system. Our observations were carried out at OASI and SOAR between 2021…

We describe the physical and orbital properties of C/2011 W3. After surviving perihelion, the comet underwent major changes (permanent loss of nuclear condensation, formation of spine tail). The process of disintegration culminated with an…

Intrinsically faint comets in nearly-parabolic orbits with perihelion distances much smaller than 1 AU exhibit strong propensity for suddenly disintegrating at a time not long before perihelion, as shown by Bortle (1991). Evidence from…

We present observations of comet 67P/Churyumov-Gerasimenko during its 2021/22 apparition, aiming to investigate its dust and gas environment and compare the results with those obtained in 2015/16 using the same telescope. Quasi-simultaneous…

We used the UltraViolet-Optical Telescope on board Swift to observe the dynamically young comet C/2009 P1 (Garradd) from a heliocentric distance of 3.5 AU pre-perihelion until 4.0 AU outbound. At 3.5 AU pre-perihelion, comet Garradd had one…

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…

We analyse data on the post-perihelion morphology, including jet position angles (PAs) and coma dominated photometry of the interstellar object 3I/ATLAS. From Hubble Space Telescope (HST) images processed with a Larson Sekanina rotational…

The nature of the newly discovered fast blue optical transients (FBOTs) is still puzzling astronomers. In this paper we carry out a comprehensive analysis of the molecular gas, ionized gas and stellar populations in the environment of the…

{The multiple outburst events of comet 12P/Pons-Brooks during its 2024 apparition offer a unique window into highly-active volatile releasing processes not observable during quiescent periods. We performed radio observations of comet…

We present our results for comet (ISON). Our results were obtained with amateur telescopes observing from the ground, before and after the comet had passed conjunction with the Sun in August 2013. We measured a mean radius of 830 +- 245 m,…