scholarly journals Comet C/2018 V1 (Machholz–Fujikawa–Iwamoto): dislodged from the Oort Cloud or coming from interstellar space?

2019 ◽  
Vol 489 (1) ◽  
pp. 951-961 ◽  
Author(s):  
C de la Fuente Marcos ◽  
R de la Fuente Marcos
Keyword(s):  
Solar System ◽  
Dynamical Evolution ◽  
Oort Cloud ◽  
Interstellar Space ◽  
The Sun ◽  
The Past ◽  
Using Data ◽  
To Receive ◽  
Practical Feasibility

ABSTRACT The chance discovery of the first interstellar minor body, 1I/2017 U1 (‘Oumuamua), indicates that we may have been visited by such objects in the past and that these events may repeat in the future. Unfortunately, minor bodies following nearly parabolic or hyperbolic paths tend to receive little attention: over 3/4 of those known have data-arcs shorter than 30 d and, consistently, rather uncertain orbit determinations. This fact suggests that we may have observed interstellar interlopers in the past, but failed to recognize them as such due to insufficient data. Early identification of promising candidates by using N-body simulations may help in improving this situation, triggering follow-up observations before they leave the Solar system. Here, we use this technique to investigate the pre- and post-perihelion dynamical evolution of the slightly hyperbolic comet C/2018 V1 (Machholz–Fujikawa–Iwamoto) to understand its origin and relevance within the context of known parabolic and hyperbolic minor bodies. Based on the available data, our calculations suggest that although C/2018 V1 may be a former member of the Oort Cloud, an origin beyond the Solar system cannot be excluded. If extrasolar, it might have entered the Solar system from interstellar space at low relative velocity with respect to the Sun. The practical feasibility of this alternative scenario has been assessed within the kinematic context of the stellar neighbourhood of the Sun, using data from Gaia second data release, and two robust solar sibling candidates have been identified. Our results suggest that comets coming from interstellar space at low heliocentric velocities may not be rare.

scholarly journals Galactic tide and local stellar perturbations on the Oort cloud: creation of interstellar comets

2019 ◽  
Vol 629 ◽  
pp. A139 ◽  
Author(s):  
S. Torres ◽  
M. X. Cai ◽  
A. G. A. Brown ◽  
S. P. Zwart
Keyword(s):  
Dynamical Evolution ◽  
Cumulative Effect ◽  
Oort Cloud ◽  
Radial Velocities ◽  
Current Status ◽  
Interstellar Space ◽  
The Sun ◽  
Semi Major Axis ◽  
Software Environment ◽  
External Perturbations

Comets in the Oort cloud evolve under the influence of internal and external perturbations, such as giant planets, stellar passages, and the Galactic gravitational tidal field. We aim to study the dynamical evolution of the comets in the Oort cloud, accounting for the perturbation of the Galactic tidal field and passing stars. We base our study on three main approaches; analytic, observational, and numerical. We first construct an analytical model of stellar encounters. We find that individual perturbations do not modify the dynamics of the comets in the cloud unless very close (<0.5 pc) encounters occur. Using proper motions, parallaxes, and radial velocities from Gaia DR2 and combining them with the radial velocities from other surveys, we then construct an astrometric catalogue of the 14 659 stars that are within 50 pc of the Sun. For all these stars we calculate the time and distance of closest approach to the Sun. We find that the cumulative effect of relatively distant (≤1 pc) passing stars can perturb the comets in the Oort cloud. Finally, we study the dynamical evolution of the comets in the Oort cloud under the influence of multiple stellar encounters from stars that pass within 2.5 pc of the Sun and the Galactic tidal field over ±10 Myr. We use the Astrophysical Multipurpose Software Environment (AMUSE), and the GPU-accelerated direct N-body code ABIE. We considered two models for the Oort cloud, compact (a ≤ 0.25 pc) and extended (a ≤ 0.5 pc). We find that the cumulative effect of stellar encounters is the major perturber of the Oort cloud for a compact configuration while for the extended configuration the Galactic tidal field is the major perturber. In both cases the cumulative effect of distant stellar encounters together with the Galactic tidal field raises the semi-major axis of ~1.1% of the comets at the edge of the Oort cloud up to interstellar regions (a > 0.5 pc) over the 20 Myr period considered. This leads to the creation of transitional interstellar comets (TICs), which might become interstellar objects due to external perturbations. This raises the question of the formation, evolution, and current status of the Oort cloud as well as the existence of a “cloud” of objects in the interstellar space that might overlap with our Oort cloud, when considering that other planetary systems should undergo similar processes leading to the ejection of comets.

scholarly journals No evidence for interstellar planetesimals trapped in the Solar system

2020 ◽  
Vol 497 (1) ◽  
pp. L46-L49 ◽  
Author(s):  
A Morbidelli ◽  
K Batygin ◽  
R Brasser ◽  
S N Raymond
Keyword(s):  
Solar System ◽  
Oort Cloud ◽  
Giant Planets ◽  
Asteroid Belt ◽  
Interstellar Space ◽  
Fast Decay ◽  
Early Solar System ◽  
The Past ◽  
Solar System Bodies ◽  
Main Asteroid Belt

ABSTRACT In two recent papers published in MNRAS, Namouni and Morais claimed evidence for the interstellar origin of some small Solar system bodies, including: (i) objects in retrograde co-orbital motion with the giant planets and (ii) the highly inclined Centaurs. Here, we discuss the flaws of those papers that invalidate the authors’ conclusions. Numerical simulations backwards in time are not representative of the past evolution of real bodies. Instead, these simulations are only useful as a means to quantify the short dynamical lifetime of the considered bodies and the fast decay of their population. In light of this fast decay, if the observed bodies were the survivors of populations of objects captured from interstellar space in the early Solar system, these populations should have been implausibly large (e.g. about 10 times the current main asteroid belt population for the retrograde co-orbital of Jupiter). More likely, the observed objects are just transient members of a population that is maintained in quasi-steady state by a continuous flux of objects from some parent reservoir in the distant Solar system. We identify in the Halley-type comets and the Oort cloud the most likely sources of retrograde co-orbitals and highly inclined Centaurs.

scholarly journals Jupiter’s decisive role in the inner Solar System’s early evolution

2015 ◽  
Vol 112 (14) ◽  
pp. 4214-4217 ◽  
Author(s):  
Konstantin Batygin ◽  
Greg Laughlin
Keyword(s):  
Solar System ◽  
Dynamical Evolution ◽  
Decisive Role ◽  
Terrestrial Planets ◽  
The Sun ◽  
Mean Motion Resonances ◽  
The Earth ◽  
Short Period ◽  
Orbital Periods ◽  
Gas Drag

The statistics of extrasolar planetary systems indicate that the default mode of planet formation generates planets with orbital periods shorter than 100 days and masses substantially exceeding that of the Earth. When viewed in this context, the Solar System is unusual. Here, we present simulations which show that a popular formation scenario for Jupiter and Saturn, in which Jupiter migrates inward from a > 5 astronomical units (AU) to a ≈ 1.5 AU before reversing direction, can explain the low overall mass of the Solar System’s terrestrial planets, as well as the absence of planets with a < 0.4 AU. Jupiter’s inward migration entrained s ≳ 10−100 km planetesimals into low-order mean motion resonances, shepherding and exciting their orbits. The resulting collisional cascade generated a planetesimal disk that, evolving under gas drag, would have driven any preexisting short-period planets into the Sun. In this scenario, the Solar System’s terrestrial planets formed from gas-starved mass-depleted debris that remained after the primary period of dynamical evolution.

scholarly journals Formation of Outer Solar System Bodies: Comets and Planetesimals

1994 ◽  
Vol 160 ◽  
pp. 443-459
Author(s):  
Mark E. Bailey
Keyword(s):  
Solar System ◽  
Surface Density ◽  
Interstellar Dust ◽  
Main Sequence ◽  
Planetary System ◽  
Gravitational Instability ◽  
Sharp Decrease ◽  
Oort Cloud ◽  
Interstellar Space ◽  
Outer Planets

Observations of massive, extended discs around both pre-main-sequence and main-sequence stellar systems indicate that protoplanetary discs larger than the observed planetary system are a common phenomenon, while the existence of large comets suggests that the total cometary mass is much greater than previous estimates. Both observations suggest that theories of the origin of the solar system are best approached from the perspective provided by theories of star formation, in particular that the protoplanetary disc may have extended up to ~103 AU. A model with a surface density distribution similar to a minimum-mass solar nebula, but extending further in radius, is derived by considering the gravitational collapse of a uniform, slowly rotating molecular cloud. The boundary of the planetary system is determined not by lack of mass, as in previous ‘mass-limited’ models (i.e. those with a sharp decrease in surface density Σ beyond the radius of the observed planetary system), but instead by the increasing collision time between the comets or planetesimals initially formed by gravitational instability beyond the planetary zone. Bodies formed beyond ~50 AU have sizes on the order of 102 km and represent a collisionally unevolved population; they are composed of relatively small, unaltered clumps of interstellar dust and ices with individual sizes estimated to range up to ~10 m. By contrast, bodies formed closer in, for example in the Uranus-Neptune zone, consist of larger agglomerations of dust and ices with individual sizes ranging up to ~1 km. Planetesimals formed by gravitational instability at smaller heliocentric distances r are typically much smaller than those formed further out, the masses mp being proportional to Σ3r6, but subsequent collisional aggregation in the planetary region is expected to produce bodies with sizes ranging up to 102 km or more. In both cases the first-formed solid objects may be identified with observed cometary nuclei; some accumulate to produce the outer planets, but the majority are ejected, either to interstellar space or into the Oort cloud. Observed comets represent a dynamically well-mixed group from various sources; they are expected to comprise a heterogeneous mix of both pristine and relatively altered material and to have a broad mass distribution ranging up to the size of the largest planetesimals.

Approaches of stars to the Sun

1999 ◽  
Vol 173 ◽  
pp. 345-352 ◽  
Author(s):  
P.A. Dybczyński ◽  
P. Kankiewicz
Keyword(s):  
Minimum Distance ◽  
Galactic Disk ◽  
Equations Of Motion ◽  
Oort Cloud ◽  
The Sun ◽  
The Past ◽  
Straight Line ◽  
The Galaxy ◽  
Hipparcos Catalogue ◽  
Nearby Stars

AbstractClose approaches of stars to the Solar System perturb comets from the Oort cloud so that they pass into the planetary system − the gravitational impulse changes the distribution of observable comets. This paper presents the results of calculations of the motion of stars in the solar neighbourhood in the past and future. The main results for each star are: the time of the encounter and the minimum distance between the Sun and the star. They are calculated using three different methods: a straight line motion model, a model with a Sun − star Keplerian interaction, and the numerical integration of the equations of motion with galactic perturbations included. In the last case, two models of the Galactic potential are used: a simplified potential of the Galactic disk and the more complex potential of the Galaxy by Dauphole and Colin. Coordinates and velocities of nearby stars are taken from several different catalogues: the Gliese catalogue, the Hipparcos catalogue, and the Barbier-Brossat catalogue of Radial Velocities.

From the Solar system comet cloud to near-Earth space

1999 ◽  
Vol 173 ◽  
pp. 339-344 ◽  
Author(s):  
V.V. Emel'yanenko
Keyword(s):  
Steady State ◽  
Solar System ◽  
Dynamical Evolution ◽  
Oort Cloud ◽  
High Eccentricity ◽  
Earth Space ◽  
Near Earth Space ◽  
Short Period ◽  
Absolute Magnitudes ◽  
Continuous Source

AbstractThe dynamical evolution of objects from different zones of the solar system comet cloud to near-Earth space has been investigated. The steady-state number of objects with perihelion distancesq&lt; 1.5 AU and periodsP &lt;20 yr, arising from the near-parabolic flux of comets with absolute magnitudes brighter thanH10= 7 is ∼ 200 − 1000. The corresponding number for Halley-type comets is hundreds of times larger than the number of known Halley-type comets. The flux of objects in the Centaurs zone, captured from the near-parabolic flux is 300 times as large as the flux of new comets. The total number of cometary objects with semi-major axesain the range 50 &lt;a&lt; 500 AU andq∼ 1 AU is ∼ 10 times as large as the number of active comets. The probability of the transfer of objects from the trans-Neptunian orbits with 35 &lt;q&lt; 50 AU anda∼ 600 AU into the Jupiter family is ∼ 0.0001. The calculations show that trans-Neptunian objects on high-eccentricity orbits can be a significant continuous source for both the replenishment of the Oort cloud and the capture to short-period orbits.

scholarly journals The completeness-corrected rate of stellar encounters with the Sun from the first Gaia data release

2017 ◽  
Vol 609 ◽  
pp. A8 ◽  
Author(s):  
C. A. L. Bailer-Jones
Keyword(s):  
Oort Cloud ◽  
Selection Function ◽  
The Sun ◽  
Accurate Analysis ◽  
The Past ◽  
Gravitational Perturbations ◽  
Galactic Potential ◽  
Data Release ◽  
Spatial Velocity ◽  
To Come

I report on close encounters of stars to the Sun found in the first Gaia data release (GDR1). Combining Gaia astrometry with radial velocities of around 320 000 stars drawn from various catalogues, I integrate orbits in a Galactic potential to identify those stars which pass within a few parsecs. Such encounters could influence the solar system, for example through gravitational perturbations of the Oort cloud. 16 stars are found to come within 2 pc (although a few of these have dubious data). This is fewer than were found in a similar study based on Hipparcos data, even though the present study has many more candidates. This is partly because I reject stars with large radial velocity uncertainties (>10 km s-1), and partly because of missing stars in GDR1 (especially at the bright end). The closest encounter found is Gl 710, a K dwarf long-known to come close to the Sun in about 1.3 Myr. The Gaia astrometry predict a much closer passage than pre-Gaia estimates, however: just 16 000 AU (90% confidence interval: 10 000–21 000 AU), which will bring this star well within the Oort cloud. Using a simple model for the spatial, velocity, and luminosity distributions of stars, together with an approximation of the observational selection function, I model the incompleteness of this Gaia-based search as a function of the time and distance of closest approach. Applying this to a subset of the observed encounters (excluding duplicates and stars with implausibly large velocities), I estimate the rate of stellar encounters within 5 pc averaged over the past and future 5 Myr to be 545 ± 59 Myr-1. Assuming a quadratic scaling of the rate within some encounter distance (which my model predicts), this corresponds to 87 ± 9 Myr-1 within 2 pc. A more accurate analysis and assessment will be possible with future Gaia data releases.

Astromaterials Research of Comet Wild 2: Terameters to Nanometers

MRS Bulletin ◽  
2010 ◽  
Vol 35 (2) ◽  
pp. 150-154 ◽  
Author(s):  
Sean Brennan
Keyword(s):  
Solar System ◽  
Elemental Abundance ◽  
The Sun ◽  
Isotopic Abundance ◽  
Solar System Formation ◽  
Sample Return ◽  
X Ray ◽  
The Past ◽  
Cometary Material ◽  
Sample Return Mission

AbstractStardust, a NASA sample return mission, safely landed in the Utah desert in January 2006 after a seven-year mission, bringing with it the first cometary material from a known parent source, Comet 81P/Wild 2. One of the mission goals is to determine the starting material of the solar system. By sampling a comet, which has spent most of the past 4.6 Gyr beyond the orbit of Neptune, we expect to measure material presumed to be unaffected by the ignition of the sun. The Stardust spacecraft swept through the tail of the comet, collecting hundreds of micron-sized particles from that stream into aerogel, a low-density silica foam. An international team of materials scientists have studied the mineralogy, petrology, and elemental and isotopic abundance of these materials. Our group has studied elemental abundance using an x-ray microprobe; the morphology of the particles was examined using an x-ray microscope, which enables nanotomography of the particles while encased in aerogel. The unexpected conclusions are that much of the material from this comet was formed near the sun, after its ignition, and soon thereafter transported to the outer reaches of the solar system. These results have changed the way astrophysicists think about solar system formation.

In Debt and Approaching Retirement: Claim Social Security or Work Longer?

2018 ◽  
Vol 108 ◽  
pp. 401-406 ◽  
Author(s):  
Barbara A. Butrica ◽  
Nadia S. Karamcheva
Keyword(s):  
Older Adults ◽  
Social Security ◽  
Labor Force ◽  
Social Security Benefit ◽  
Older Americans ◽  
The Past ◽  
Using Data ◽  
Social Security Benefits ◽  
To Receive ◽  
Retirement Study

Over the past couple of decades, older Americans have become considerably more leveraged. This paper considers whether household debt affects the timing of retirement and Social Security benefit claiming. Using data from the Health and Retirement Study, we find that older adults with debt are more likely to work and less likely to receive Social Security benefits than those who are debt-free. Indebted adults are also more likely to delay fully retiring from the labor force and claiming their benefits. Among the sources of debt, mortgages have a stronger impact on older adults' behavior than do other sources of debt.

Something about Comets

Impact! ◽  
1996 ◽  
Author(s):  
Gerrit L. Verschuur
Keyword(s):  
Nineteenth Century ◽  
Solar System ◽  
Potential Risk ◽  
Mass Extinction ◽  
Internal Heat ◽  
Interstellar Space ◽  
The Sun ◽  
Water Ice ◽  
Sandy Material ◽  
The One

Discovery of the iridium layer in the K/T boundary clay was the first clue that pointed to a cosmic impact as the trigger of the mass extinction that wiped out the dinosaurs and their associates. But what hit the earth? Was it an asteroid or a comet? To answer, we need to know something about their differences. Unfortunately, the distinction is very blurred. Comets are thought to be huge icy objects, probably with cores made of a mix of water ice and silicates (sandy material), pristine examples of the type of material out of which the solar system was formed. Some of them are hundreds of kilometers in size and they may have been built in the envelopes of gas and dust that surround cool, supergiant stars at the end of their lives. Part of the doubt about distinctions comes from trying to decide what a comet would be like after the ice evaporates. Would it then be like an asteroid? Around the end of the nineteenth century the British astronomer Sir Richard Gregory pictured comets as made up of a cloud of meteorites. He thought that when such an object was first pulled into the solar system from interstellar space it began to glow because of internal heat created as particles began to jostle one another. As the object drew closer to the sun a tail was supposed to be formed as the particles between the meteorites bumped into one another and began to escape. He did consider the potential risk to earth if it were to run into the head of a comet made up of lots of meteorites. The picture he painted was based on what an earlier astronomer, Sir Simon Newcomb, had written about this possibility. Newcomb admitted that, although there were more likely ways to die than as a result of comet collision, such a fate was real. Should such a collision, occur, Gregory conjured up a picture of what might happen. On the one hand, if the comet head was made up of dust, the earth’s inhabitants would experience nothing more than a stunning display of shooting stars. But if the comet head was made of cannonball sized objects the consequences would be dire.

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