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

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.

Download Full-text

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.

Download Full-text

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.

Download Full-text

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.

Download Full-text

Drifting Through a Planetary System

10.1093/oso/9780198799894.003.0006 ◽

2018 ◽

Author(s):

Karel Schrijver

Keyword(s):

Seventeenth Century ◽

Solar System ◽

Virtual Worlds ◽

Planetary System ◽

System P ◽

History Of ◽

Or Team ◽

Water Contents

This chapter describes how the first found exoplanets presented puzzles: they orbited where they should not have formed or where they could not have survived the death of their stars. The Solar System had its own puzzles to add: Mars is smaller than expected, while Venus, Earth, and Mars had more water—at least at one time—than could be understood. This chapter shows how astronomers worked through the combination of these puzzles: now we appreciate that planets can change their orbits, scatter water-bearing asteroids about, steal material from growing planets, or team up with other planets to stabilize their future. The special history of Jupiter and Saturn as a pair bringing both destruction and water to Earth emerged from the study of seventeenth-century resonant clocks, from the water contents of asteroids, and from experiments with supercomputers imposing the laws of physics on virtual worlds.

Download Full-text

The Principle of Least Interaction Action

Highlights of Astronomy ◽

10.1017/s1539299600002240 ◽

1974 ◽

Vol 3 ◽

pp. 489-489

Author(s):

M. W. Ovenden

Keyword(s):

Solar System ◽

Planetary System ◽

Satellite System ◽

Asteroid Belt ◽

Correct Prediction ◽

The Sun ◽

Approximate Methods ◽

Satellites Of Jupiter ◽

History Of ◽

Minimum Interaction

AbstractThe intuitive notion that a satellite system will change its configuration rapidly when the satellites come close together, and slowly when they are far apart, is generalized to ‘The Principle of Least Interaction Action’, viz. that such a system will most often be found in a configuration for which the time-mean of the action associated with the mutual interaction of the satellites is a minimum. The principle has been confirmed by numerical integration of simulated systems with large relative masses. The principle lead to the correct prediction of the preference, in the solar system, for nearly-commensurable periods. Approximate methods for calculating the evolution of an actual satellite system over periods ˜ 109 yr show that the satellite system of Uranus, the five major satellites of Jupiter, and the five planets of Barnard’s star recently discovered, are all found very close to their respective minimum interaction distributions. Applied to the planetary system of the Sun, the principle requires that there was once a planet of mass ˜ 90 Mθ in the asteroid belt, which ‘disappeared’ relatively recently in the history of the solar system.

Download Full-text

Summertime PM2.5 ionic species in four major cities of China: nitrate formation in an ammonia-deficient atmosphere

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-1711-2009 ◽

2009 ◽

Vol 9 (5) ◽

pp. 1711-1722 ◽

Cited By ~ 362

Author(s):

R. K. Pathak ◽

W. S. Wu ◽

T. Wang

Keyword(s):

Gas Phase ◽

Ionic Species ◽

Mean Value ◽

Average Concentration ◽

Phase Reaction ◽

Gas Phase Reaction ◽

Particulate Pollution ◽

Aerosol Acidity ◽

Low Levels ◽

High Concentrations

Abstract. Strong atmospheric photochemistry in summer can produce a significant amount of secondary aerosols, which may have a large impact on regional air quality and visibility. In the study reported herein, we analyzed sulfate, nitrate, and ammonium in PM2.5 samples collected using a 24-h filter system at suburban and rural sites near four major cities in China (Beijing, Shanghai, Guangzhou, and Lanzhou). Overall, the PM2.5 mass concentrations were high (with a mean value of 55–68 gμgm−3), which reflects the long-known particulate pollution in China's large urban centers. We observed very high concentrations of sulfate and nitrate at the Beijing and Shanghai sites, and, in particular, abnormally high levels of nitrate (24-h average concentration up to 42 gμgm−3 and contributing up to 25% of the PM2.5 mass) in the ammonium-poor samples. The Beijing and Shanghai aerosols were characterized by high levels of aerosol acidity (~220–390 nmol m−3) and low levels of in-situ pH (−0.77 to −0.52). In these samples, the formation of the observed high concentrations of particulate nitrate cannot be explained by homogeneous gas-phase reaction between ammonia and nitric acid. Examination of the relation of nitrate to relative humidity and aerosol loading suggests that the nitrate was most probably formed via the heterogeneous hydrolysis of N2O5 on the surface of the moist and acidic aerosols in Beijing and Shanghai. In comparison, the samples collected in Lanzhou and Guangzhou were ammonium-rich with low levels of aerosol acidity (~65–70 nmol m−3), and the formation of ammonium nitrate via the homogeneous gas-phase reaction was favored, which is similar to many previous studies. An empirical fit has been derived to relate fine nitrate to aerosol acidity, aerosol water content, aerosol surface area, and the precursor of nitrate for the data from Beijing and Shanghai.

Download Full-text

Properties of the circumgalactic medium in simulations compared to observations

Astronomy and Astrophysics ◽

10.1051/0004-6361/201628886 ◽

2018 ◽

Vol 609 ◽

pp. A66 ◽

Cited By ~ 3

Author(s):

R. E. G. Machado ◽

P. B. Tissera ◽

G. B. Lima Neto ◽

L. Sodré

Keyword(s):

Gas Phase ◽

Chemical Elements ◽

Star Forming ◽

Physical Conditions ◽

Cosmological Context ◽

Circumgalactic Medium ◽

Hydrodynamical Simulations ◽

Stellar Masses ◽

Lower Limits ◽

Supernova Feedback

Context. Galaxies are surrounded by extended gaseous halos that store significant fractions of chemical elements. These are syntethized by the stellar populations and later ejected into the circumgalactic medium (CGM) by different mechanism, of which supernova feedback is considered one of the most relevant. Aims. We aim to explore the properties of this metal reservoir surrounding star-forming galaxies in a cosmological context aiming to investigate the chemical loop between galaxies and their CGM, and the ability of the subgrid models to reproduce observational results. Methods. Using cosmological hydrodynamical simulations, we have analysed the gas-phase chemical contents of galaxies with stellar masses in the range 109−1011 M⊙. We estimated the fractions of metals stored in the different CGM phases, and the predicted O vi and Si iii column densities within the virial radius. Results. We find roughly 107 M⊙ of oxygen in the CGM of simulated galaxies having M⋆ ~ 1010 M⊙, in fair agreement with the lower limits imposed by observations. The Moxy is found to correlate with M⋆, at odds with current observational trends but in agreement with other numerical results. The estimated profiles of O vi column density reveal a substantial shortage of that ion, whereas Si iii, which probes the cool phase, is overpredicted. Nevertheless, the radial dependences of both ions follow the respective observed profiles. The analysis of the relative contributions of both ions from the hot, warm and cool phases suggests that the warm gas (105 K < T < 106 K) should be more abundant in order to bridge the mismatch with the observations, or alternatively, that more metals should be stored in this gas-phase. These discrepancies provide important information to improve the subgrid physics models. Our findings show clearly the importance of tracking more than one chemical element and the difficulty of simultaneously satisfying the observables that trace the circumgalactic gas at different physical conditions. Additionally, we find that the X-ray coronae around the simulated galaxies have luminosities and temperatures in decent agreement with the available observational estimates.

Download Full-text

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.

Download Full-text