Some active processes in comet icy nuclei: nucleus splitting and anti tail formation

AbstractThe most dramatic display of variable activity of a comet is splitting of the nucleus. For the purpose of revealing the trends of splitting of comet nuclei and of formation of abnormal cometary tails, we have created two catalogues of comets: a catalogue of split nuclei, containing 99 comets, and a catalogue of comets with abnormal tails, including 60 objects. Statistical investigation reveals some general trends of these phenomena. The greatest number of recorded cases of nucleus splitting and abnormal tail (60%) occurs within an interval of heliocentric distance ranging from 0.6 AU to 1.6 AU (maximum at 1.1 AU) and geocentric distance ranging from 0.6 AU to 1.8 AU (maximum at 1.15 AU). Splitting of nuclei and abnormal tails are more often (75%) recorded close to the perihelia of the cometary orbits. Only 16% of splitting comets also exhibit abnormal tails. Some cases of nuclear splitting and large velocity (some km/s) eruptions of dust from a nucleus, as well as cases of abnormal tails developed at large heliocentric distances, may indicate collisions of comet nuclei with other bodies. Our results are of interest for the physics of comets, and for the distribution of meteoroids in solar system.

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Narrow-band photometry of Long Period Comets with TRAPPIST telescopes in 2019-2020

10.5194/epsc2020-419 ◽

2020 ◽

Author(s):

Youssef Moulane ◽

Emmanuel Jehin ◽

Francisco José Pozuelos ◽

Jean Manfroid ◽

Zouhair Benkhaldoun ◽

...

Keyword(s):

Solar System ◽

Production Rate ◽

Heliocentric Distance ◽

Narrow Band ◽

Maximum Activity ◽

The Sun ◽

Water Production ◽

Dust Production ◽

Long Period ◽

Water Production Rate

Long Period Comets (LPCs) have orbital periods longer than 200 years, perturbed from their resting place in the Oort cloud. Such gravitational influences may send these icy bodies on a path towards the center of the Solar system in highly elliptical orbits. In this work, we present the activity and composition evolution of several LPCs observed with both TRAPPIST telescopes (TS and TN) during the period of 2019-2020. These comets include: C/2017 T2 (PANSTARRS), C/2018 Y1 (Iwamoto), C/2018 W2 (Africano), and disintegrated comet C/2019 Y4 (ATLAS). We monitored the OH, NH, CN, C2 and C3 production rates evolution and their chemical mixing ratios with respect to their distances to the Sun as well as the dust production rate proxy (A(0)fp) during the journey of these comets into the inner Solar system. C/2017 T2 (PANSTARRS) is a very bright comet which was discovered on October 2, 2017 when it was 9.20 au from the Sun. We started observing this comet with TS at the beginning of August 2019 when it was at 3.70 au. The comet made the closest approach to the Earth on December 28, 2019 at a distance of 1.52 au and it passed the perihelion on May 4, 2020 at 1.61 au. The water production rate of the comet reached a maximum of (4,27&#177;0,12)1028 molecules/s and its dust production rate (A(0)fp(RC)) also reached the peak of 5110&#177;25 cm on January 26, 2020, when the comet was at 2.08 au from the Sun (-100 days pre-perihelion). At the time of writing, we still monitoring the activity of the comet with TN at heliocentric distance of 1.70 au. Our observations show that C/2017 T2 is a normal LPC. C/2018 Y1 (Iwamoto) is a nearly parabolic comet with a retrograde orbit discovered on December 18, 2018 by Japanese amateur astronomer Masayuki Iwamoto. We monitored the activity and composition of Iwamoto with both TN and TS telescopes from January to March 2019. The comet reached its maximum activity on January 29, 2019 when it was at 1.29 au from the Sun (-8 days pre-perihelion) with Q(H2O)=(1,68&#177;0,05)1028 molecules/s and A(0)fp(RC)= 92&#177;5 cm. These measurements show that it was a dust-poor comet compared to the typical LPCs. C/2018 W2 (Africano) was discovered on November 27, 2018 at Mount Lemmon Survey with a visual magnitude of 20. The comet reached its perihelion on September 6, 2019 when it was at 1.45 au from the Sun. We monitored the comet from July 2019 (rh=1.71 au) to January 2020 (rh=2.18 au) with both TN and TS telescopes. The comet reached its maximum activity on September 21, 15 days post-perihelion (rh=1.47 au) with Q(H2O)=(0,40&#177;0,03)1028 molecules/s. C/2019 Y4 (ATLAS) is a comet with a nearly parabolic orbit discovered on December 18, 2019 by the ATLAS survey. We started to follow its activity and composition with broad- and narrow-band filters with the TN telescope on February 22, 2019 when it was at 1.32 au from the Sun until May 3, 2020 when the comet was at a heliocentric distance of 0.90 au inbound. The comet activity reached a maximum on March 22 (rh=1.65 au) 70 days before perihelion. At that time, the water-production rate reached (1,53&#177;0,04)1028 molecules/s and the A(0)fp reached (1096&#177;14) cm in the red filter. After that, the comet began to fade and disintegrated into several fragments.

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The Symmetry Plane of the Zodiacal Cloud Near 1 AU

Symposium - International Astronomical Union ◽

10.1017/s0074180900066468 ◽

1980 ◽

Vol 90 ◽

pp. 49-53

Author(s):

Nebil Y. Misconi

Keyword(s):

Solar System ◽

Heliocentric Distance ◽

Symmetry Plane ◽

Orbital Plane ◽

Zodiacal Light ◽

Zodiacal Cloud ◽

Invariable Plane

Analysis of zodiacal light observations from Mt. Haleakala, Hawaii show that the symmetry plane of the zodiacal cloud near 1 A.U. is close to the invariable plane of the solar system. Since the symmetry plane of the inner zodiacal cloud is close to the orbital plane of Venus (Misconi and Weinberg, 1978; Leinert et al., 1979), we suggest that the symmetry plane changes inclination with heliocentric distance.

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The Planetenteleskop Mission

International Astronomical Union Colloquium ◽

10.1017/s0252921100077149 ◽

1990 ◽

Vol 123 ◽

pp. 286-286

Author(s):

G. Neukum

Keyword(s):

Solar System ◽

Time Variable ◽

Image Correlation ◽

Tracking Accuracy ◽

Cometary Nuclei ◽

Planetary Environments ◽

Science Community ◽

Active Processes ◽

Time Invariant ◽

Accuracy And Stability

AbstractThe scientific focus of the Planetenteleskop project will be on time-variable solar system phenomena (planet-magnetosphere-satellite interactions, active processes of cometary nuclei, atmospheric circulation and dynamics), on time-invariant solar system phenomena (geochemical provinces on planetary and satellite surfaces, global characteristics of primitive bodies), on planetary environments of other stars, and on general astronomical and astrophysical applications. The proposed Planetenteleskop in elliptical 24 h earth orbit will combine near-simultaneous, high-resolution spectroscopic observations, diffraction-limited imaging quality, long integration times (< 10 h) and excellent target tracking accuracy (nominally 0.05 arc sec/10 h, up to 0.02 arc sec). The excellent tracking accuracy and stability on extended objects and features is provided by a novel real-time on-board image correlation scheme. The Planetenteleskop has been studied in prephase A and phase A by industry and the involved science community in Germany in cooperation with American colleagues.

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Cometary volatiles

Symposium - International Astronomical Union ◽

10.1017/s0074180900009372 ◽

1997 ◽

Vol 178 ◽

pp. 219-236 ◽

Cited By ~ 8

Author(s):

D. Bockelee-Morvan

Keyword(s):

Solar System ◽

Heliocentric Distance ◽

Solar Nebula ◽

Current Knowledge ◽

Close Approach ◽

Interstellar Material

Comets are believed to be the most pristine material surviving from the origin of the Solar System. The nature of their volatiles should in principle provide chemical and physical clues to their formation environment in the solar nebula. Another important aspect of the study of comets is the extent to which they may incorporate relatively unprocessed interstellar material.Our knowledge of the composition of cometary ices has been greatly improved in this last decade. The years 1995-1996 were rich in new results, with the close approach to Earth of comet C/1996 B2 Hyakutake and the discovery of the bright comet C/1995 O1 Hale-Bopp at large heliocentric distance. We will present the current knowledge of the nature and abundances of cometary volatiles and mention some of the outstanding issues related to the origin of comets and their links to interstellar material.

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Asteroid compositional «rings»: clues to the compositions of primordial planetesimals in the middle solar system

International Astronomical Union Colloquium ◽

10.1017/s0252921100101812 ◽

1984 ◽

Vol 75 ◽

pp. 703-712

Author(s):

E.F. Tedesco

Keyword(s):

Solar System ◽

Final Stage ◽

Heliocentric Distance ◽

Solar Nebula ◽

Satellite System ◽

Asteroid Belt ◽

Planetary Rings ◽

Early Solar System ◽

Physical Conditions

ABSTRACTIt has recently been established that the distribution of asteroid taxonomic types at distances between 2.1 and 5.3 astronomical units is highly structured. There are four major, overlapping but nevertheless compositionally distinct, “rings” of asteroids present within this range of heliocentric distance. These “rings”, within which ~ 80% of each of four major taxonomic types (S, C, P, and D) fall, are centered at 2.6 (0.7), 2.9 (0.8), 3.4 (0.7), and 4.6 (1.5) AU respectively, where the numbers within parentheses are the ring “widths” in AU. The overall physical resemblence between the asteroid “rings” and planetary rings is poor; physically the asteroid belt more closely resembles a debris strewn satellite system. This structure is consistent with these objects having been formed directly from the solar nebula at, or near, the heliocentric distances at which we find them today. Once the mineralogy of these taxonomic types is firmly established, and complications arising from post-accreationary metamorphism are dealt with, they may be used as probes of physical conditions in the early solar system. In particular, the identification of primordial planetesimals will allow us to obtain a first-hand look at the siblings of the planetesimals responsible for the final stage of planetary accretion.

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Comets : A Key to Solar System Formation

Zeitschrift für Naturforschung A ◽

10.1515/zna-1989-1001 ◽

1989 ◽

Vol 44 (10) ◽

pp. 867-876

Author(s):

Horst Uwe Keller

Keyword(s):

Solar System ◽

Heliocentric Distance ◽

Planetary System ◽

Cometary Nucleus ◽

Interplanetary Dust ◽

Dust Particles ◽

Interplanetary Dust Particles ◽

The Earth ◽

Comet Halley

Abstract Four lines of information on comets are discussed: their orbits, their relation to other bodies of the planetary system, their physical state and chemical composition, and implications of recent observations of the nucleus of comet Halley. The in situ measurements during the flybys of comet Halley strongly support the assumption that comets are members of the solar system and were created during its formation. The region (heliocentric distance) of their formation is, however, still difficult to assess. The size, shape, and topography of the cometary nucleus suggest that it was formed from relatively large subnuclei in a region of the primordial solar nebula where relative velocities were sufficiently small. There are indications that some of the interplanetary dust particles in the Earth atmosphre may originate from comets.

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Chemistry in carbon-rich protoplanetary disks: Effect of carbon grain destruction

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318008633 ◽

2018 ◽

Vol 14 (S345) ◽

pp. 289-290

Author(s):

Chen-En Wei ◽

Hideko Nomura ◽

Jeong-Eun Lee ◽

Wing-Huen Ip ◽

Catherine Walsh ◽

...

Keyword(s):

Solar System ◽

Heliocentric Distance ◽

Reaction Network ◽

Protoplanetary Disks ◽

Carbon Chain ◽

Disk Radius ◽

Model Calculations ◽

Chain Molecules ◽

Physical Conditions ◽

Solar System Objects

AbstractThe Earth is dramatically carbon poor comparing to the interstellar medium and the proto-sun. The carbon to silicon ratios in inner solar system objects show a correlation with heliocentric distance, which suggests that the destruction of carbon grains has occurred before planet formation. To examine this hypothesis, we perform model calculations using a chemical reaction network under the physical conditions typical of protoplanetary disks. Our results show that, when carbonaceous grains are destroyed and converted into the gas phase and the gas becomes carbon-rich, the abundances of carbon-bearing species such as HCN and carbon-chain molecules, increase dramatically near the midplane, while oxygen-bearing species such as H2O and CO2 are depleted. The carbon to silicon ratios obtained by our model calculations qualitatively reproduce the observed gradient with disk radius, but there are some quantitative discrepancies from the observed values of the solar system objects. We adopted the model of a disk around a Herbig Ae star and performed line radiative transfer calculations to examine the effect of carbon grain destruction through observations with ALMA. The results indicate that HCN, H13 CN and c-C3 H2 may be good tracers of this process.

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1.3.3 Consequences of the Inclination of the Zodiacal Cloud on the Ecliptic

International Astronomical Union Colloquium ◽

10.1017/s0252921100051575 ◽

1976 ◽

Vol 31 ◽

pp. 121-121

Author(s):

R. Robley

Keyword(s):

Solar System ◽

Exponential Distribution ◽

Inclination Angle ◽

Radial Direction ◽

Heliocentric Distance ◽

Ecliptic Plane ◽

Interplanetary Dust ◽

Zodiacal Light ◽

Invariant Plane ◽

Zodiacal Cloud

Assuming that the decrease in the density of the interplanetary dust follows an exponential distribution both in the transverse and radial direction, we can write n = no Exp(-(h/H)-(r-l/R)), where h is the distance from the ecliptic plane and r the heliocentric distance both expressed in astronomical units (a.u.); then we show that the modulation of the radiance B(90, 0) of the zodiacal light observed at the ecliptic pole defines the parameter H as a function of the inclination angle B between the zodiacal cloud and the ecliptic plane; moreover, the experimental value of the ratio B(90, 0)/B(90, 90) defines the parameter R. It can be deduced that the flatness of the zodiacal cloud, expressed by R/H, is < 5 and that the plane of symmetry of the zodiacal cloud is very close to that of the invariant plane of the solar system (B<2°).

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Gas-phase Modeling of the Cometary Coma of Interstellar Comet 2I/Borisov

The Astrophysical Journal ◽

10.3847/1538-4357/ac2a42 ◽

2021 ◽

Vol 923 (1) ◽

pp. 91

Author(s):

Sana Ahmed ◽

Kinsuk Acharyya

Keyword(s):

Solar System ◽

Gas Phase ◽

Energy Exchange ◽

Heliocentric Distance ◽

Planetary System ◽

Vibrational Excitation ◽

Ionic Species ◽

Inelastic Collisions ◽

Organic Ions ◽

Physical Conditions

Abstract Comet 2I/Borisov is the first interstellar comet observed in the solar system, providing a unique opportunity to understand the physical conditions that prevailed in a distant unknown planetary system. Observations of the comet show that the CO/H2O ratio is higher than that observed in solar system comets at a heliocentric distance r h < 2.5 au. We aim to study the gas-phase coma of comet 2I/Borisov using a multifluid chemical-hydrodynamical model. The gas-phase model includes a host of chemical reactions, with the neutrals, ions, and electrons treated as three separate fluids. Energy exchange between the three fluids due to elastic and inelastic scattering and radiative losses are also considered. Our model results show that in the region of the coma beyond ∼100 km of the nucleus, e−−CO inelastic collisions leading to vibrational excitation of CO causes a loss of energy from the electron fluid. We find a high abundance of CO+ and HCO+ ions, and we show how these two ions affect the creation/destruction rates of other ions such as H2O+, H3O+, N-bearing ions, and large organic ions. We find that the presence of CO leads to a higher abundance of large organic ions and neutrals such as CH 3 OH 2 + , CH 3 OCH 4 + , and CH3OCH3, as compared to a typical H2O-rich solar system comet. We conclude that the presence of a large amount of CO in the coma of comet 2I/Borisov, combined with a low production rate, affects the coma temperature profile and flux of major ionic species significantly.

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Clathrate hydrates FTIR spectroscopy to understand cometary ices

10.5194/epsc2021-396 ◽

2021 ◽

Author(s):

Natalia Esteves Lopez ◽

Aurélie Guilbert-Lepoutre ◽

Stéphane Coussan ◽

Joëlle Mascetti ◽

Arnaud Desmedt ◽

...

Keyword(s):

Solar System ◽

Gas Hydrates ◽

Clathrate Hydrates ◽

Water Molecules ◽

The European Union ◽

Volatile Species ◽

Horizon 2020 ◽

Research And Innovation ◽

Cometary Material ◽

Comet Nuclei

Comet nuclei in the transneptunian region are submitted to&#160; heating at temperatures from 30 to 50 K over the age of the solar system [1]. The timescale for sublimated volatiles to escape the objects at these temperatures is long though [1]. Once these nuclei enter the inner solar system and become active, subsurface sublimation puts a gas phase in contact of the porous and tortuous ice structure of cometary material. In this context, the formation of clathrate hydrates may be considered as a plausible trapping mechanism of these gases, occurring in subsurface layers, and allowing some of the most volatile species to subsequently survive in cometary material at temperatures higher than the sublimation temperature of the corresponding pure solid [2].&#160; Hydrates are ice-like crystalline compounds, resulting from the tridimensional stacking of cages of H-bonded water molecules. Clathrates are gas hydrates, meaning that the guests are gas molecules encased in a host framework of water molecules. Gas hydrates only form and remain stable in specific temperature and pressure regimes that depend on the nature of the guest molecules [3]. Theoretical phase diagram of clathrate hydrates show that it would be possible to form clathrates at very low pressure (10-10 bar) and temperature (< 80 K), but there is a critical lack of experimental data using these preparation methods [4]. Could clathrate hydrates be formed under conditions relevant to the interior of comet nuclei?&#160; The formation and characterization of these ice-like structures under such conditions could provide valuable experimental evidence for understanding the preservation of some volatile species during the thermally-induced evolution of comets.&#160; In an effort to assess whether hydrates may play a role in maintaining volatile species in cometary material, FTIR spectroscopic identification of several species have been performed. We present results related to carbon dioxide and methane hydrates, in conditions relevant to cometary nuclei, i.e. at low temperature (10 K) and pressure (base pressure 10-7 mbar) regimes. To understand the nature of the gas hydrates formed under these conditions, vibrational spectra of distinct gas/ice interactions (clathrate hydrate, gas in/on water ice) were compared. The behaviour of the water crystalline skeleton interactions with the trapped molecules at different temperatures, as well as the influence of the gas mixture and the deposition method, will be presented. &#160; Acknowledgements This study is part of a project that has received funding from the European Research Council (ERC) under the European Union&#8217;s Horizon 2020 research and innovation programme (Grant agreement No. 802699).&#160; &#160; [1] Prialnik et al. (2004) in Comets II, Festou, Keller and Weaver (Eds.), 359-387 [2] Mandt et al. (2017) in Comets as Tracers of Solar System Formation and Evolution, Mandt, Mousis, Bockel{\'e}e-Morvan and Russel (Eds.) [3] Sloan (2003) Nature, 426, 353-359 [4] Choukroun et al. (2003) in The Science of Solar System Ices, Gudipati and Castillo-Roguez (Eds.), 409-454&#160;

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