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Thread: How often do we get close passages?

  1. #31
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    Several papers have recently focused on Scholz's Star, WISE J072003.20-084651.2, which apparently made a close flyby within human existence, though not within human history. Again, papers are listed most recent first, then on back in time. The last paper is the actual discovery paper for Scholz's Star.

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    http://adsabs.harvard.edu/abs/2018MNRAS.476L...1D

    Where the Solar system meets the solar neighbourhood: patterns in the distribution of radiants of observed hyperbolic minor bodies

    de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl; Aarseth, Sverre J.
    05/2018

    Observed hyperbolic minor bodies might have an interstellar origin, but they can be natives of the Solar system as well. Fly-bys with the known planets or the Sun may result in the hyperbolic ejection of an originally bound minor body; in addition, members of the Oort cloud could be forced to follow inbound hyperbolic paths as a result of secular perturbations induced by the Galactic disc or, less frequently, due to impulsive interactions with passing stars. These four processes must leave distinctive signatures in the distribution of radiants of observed hyperbolic objects, both in terms of coordinates and velocity. Here, we perform a systematic numerical exploration of the past orbital evolution of known hyperbolic minor bodies using a full N-body approach and statistical analyses to study their radiants. Our results confirm the theoretical expectations that strong anisotropies are present in the data. We also identify a statistically significant overdensity of high-speed radiants towards the constellation of Gemini that could be due to the closest and most recent known fly-by of a star to the Solar system, that of the so-called Scholz's star. In addition to and besides 1I/2017 U1 (`Oumuamua), we single out eight candidate interstellar comets based on their radiants' velocities.

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    http://adsabs.harvard.edu/abs/2015AJ....149..104B

    WISE J072003.20-084651.2: an Old and Active M9.5 + T5 Spectral Binary 6 pc from the Sun

    Burgasser, Adam J.; Gillon, Michaël; Melis, Carl; Bowler, Brendan P.; Michelsen, Eric L.; Bardalez Gagliuffi, Daniella; Gelino, Christopher R.; Jehin, E.; Delrez, L.; Manfroid, J.; Blake, Cullen H.
    03/2015

    We report observations of the recently discovered, nearby late-M dwarf WISE J072003.20-084651.2. New astrometric measurements obtained with the TRAPPIST telescope improve the distance measurement to 6.0 ± 1.0 pc and confirm the low tangential velocity (3.5 ± 0.6 km s-1) reported by Scholz. Low-resolution optical spectroscopy indicates a spectral type of M9.5 and prominent Halpha emission (< {{log }10}{{L}Halpha }/{{L}bol}> = -4.68 ± 0.06), but no evidence of subsolar metallicity or Li i absorption. Near-infrared spectroscopy reveals subtle peculiarities that can be explained by the presence of a T5 binary companion, and high-resolution laser guide star adaptive optics imaging reveals a faint (DeltaH = 4.1) candidate source 0\buildrel{\prime\prime}\over{.} 14 (0.8 AU) from the primary. With high-resolution optical and near-infrared spectroscopy, we measure a stable radial velocity of +83.8 ± 0.3 km s-1, indicative of old disk kinematics and consistent with the angular separation of the possible companion. We measure a projected rotational velocity of v sin i = 8.0 ± 0.5 km s-1 and find evidence of low-level variabilty (˜1.5%) in a 13 day TRAPPIST light curve, but cannot robustly constrain the rotational period. We also observe episodic changes in brightness (1%-2%) and occasional flare bursts (4%-8%) with a 0.8% duty cycle, and order-of-magnitude variations in Halpha line strength. Combined, these observations reveal WISE J0720-0846 to be an old, very low-mass binary whose components straddle the hydrogen burning minimum mass, and whose primary is a relatively rapid rotator and magnetically active. It is one of only two known binaries among late M dwarfs within 10 pc of the Sun, both of which harbor a mid T-type brown dwarf companion. We show that while this specific configuration is rare (≲1.6% probability), roughly 25% of binary companions to late-type M dwarfs in the local population are likely low-temperature T or Y brown dwarfs.

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    http://adsabs.harvard.edu/abs/2014A%26A...561A.113S

    Neighbours hiding in the Galactic plane, a new M/L dwarf candidate for the 8 pc sample

    Scholz, R.-D.
    01/2014

    Aims: Using Wide-field Infrared Survey Explorer (WISE) data and previous optical and near-infrared sky surveys, we try to identify still missing stellar and substellar neighbours of the Sun.
    Methods: When checking the brightest red WISE sources for proper motions and colours expected for nearby M and L dwarfs, we also approached the thin Galactic plane. Astrometry (proper motion and parallax measurements) and the available photometry were used to obtain first estimates of the distance and type of nearby candidates.
    Results: We have discovered WISE J072003.20-084651.2, an object with moderately high proper motion (mu ≈ 120 mas/yr) that lies at low Galactic latitude (b = +2.3°), with similar brightness (J ≈ 10.6, w2 ≈ 8.9) and colours (I - J ≈ 3.2, J - Ks ≈ 1.2, w1 - w2 ≈ 0.3) as the nearest known M-type brown dwarf LP 944-20. With a photometric classification as an M9 ± 1 dwarf, its photometric distance lies in the range between about 5 and 7 pc, based on comparison with absolute magnitudes of LP 944-20 alone or of a sample of M8-L0 dwarfs. The slightly larger distance derived from our preliminary trigonometric parallax (7.0 ± 1.9 pc) may indicate a close binary nature. The new neighbour is an excellent target for planet search and low-mass star/brown dwarf studies.
    There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
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  2. #32
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    Possibly the paper that started it all.

    ==============================================

    http://adsabs.harvard.edu/abs/1996EM%26P...72...19M

    Encounters of the Sun with Nearby Stars in the Past and Future

    Mülläri, A. A.; Orlov, V. V.
    02/1996

    The relative space motions of the Sun and nearby stars are considered. The coordinates and velocities of the stars are taken from the Catalogue of Nearby Stars by Gliese and Jahreiss (1991). The minimum space separation between the Sun and every star as well as the corresponding moment of time are calculated by two ways. Firstly, the straight line motions are considered. Secondly, the effect of the Galaxy potential is taken into account. The Galaxy model proposed by Kutuzov and Ossipkov (1989) is used. Twenty five stars approaching the Sun closer than two parsecs are selected. The effects of the uncertainties in the observational data are studied. The influence of the encounters to the Oort cloud is discussed.
    There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
    — Mark Twain, Life on the Mississippi (1883)

  3. #33
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    And notes about a star I have trouble finding information on in arvix

    https://en.wikipedia.org/wiki/Gamma_Microscopii
    There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
    — Mark Twain, Life on the Mississippi (1883)

  4. #34
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    Quote Originally Posted by Roger E. Moore View Post
    And notes about a star I have trouble finding information on in arvix

    https://en.wikipedia.org/wiki/Gamma_Microscopii
    Did you try searching with its HIP catalog number? The Google search string
    "HIP 103738" site:arxiv.org
    returned links to five papers, all discussing close-encounters. I haven't compared these results with papers you've already mentioned, though.

    Note: I've edited the list below, sorting it into order of increasing publication date, and adding the title of one of them.

    [PDF]Close encounters of the stellar kind
    https://arxiv.org/pdf/1412.3648
    by CAL Bailer-Jones - ‎2014 - ‎Cited by 24 - ‎Related articles
    Dec 11, 2014 - The nominal orbit of Hip 103738 (gamma Microscopii) rela- tive to the Sun in Galactic cylindrical coordinates (r, z,φ) over the past. 7.8Myr.

    [PDF]On the accuracy of close stellar approaches determination
    https://arxiv.org/pdf/1502.05518
    by PA Dybczyński - ‎2015 - ‎Cited by 20 - ‎Related articles
    Feb 19, 2015 - Distribution of clones of HIP 103738. Figure 9. Distribution of clones HIP 87052 nominal proximity points obtained on the basis of different astro ...

    [PDF]Finding the imprints of stellar encounters in long period comets
    https://arxiv.org/pdf/1509.07222
    by F Feng - ‎2015 - ‎Cited by 17 - ‎Related articles
    Oct 3, 2015 - encounters are HIP 103738 (gamma Microscopii) and HIP 14576. (Algol), both of which are massive and relatively slow. The radial velocity of ...

    [PDF]arXiv:1707.05277v4 [astro-ph.SR] 21 Dec 2017 [A CATALOGUE OF CLOSE ENCOUNTER PAIRS]
    https://arxiv.org/pdf/1707.05277
    by F Feng - ‎2017 - ‎Cited by 2 - ‎Related articles
    Dec 21, 2017 - HIP 103738 xh. 0.929 0.919 0.442 1.528. -3.85. -3.86. -4.18. -3.57. 17.97. 17.94. 16.67. 19.20. HIP 71683 xh. 0.976 0.976 0.947 1.007. 0.03.

    [PDF]New stellar encounters discovered in the second Gaia data release
    https://arxiv.org/pdf/1805.07581
    by CAL Bailer-Jones - ‎2018 - ‎Related articles
    May 19, 2018 - Hip 103738 (gamma Microscopii). This G6 giant was the potentially most massive encounter coming within 1pc in pa- per 1, found to have ...
    Selden

  5. #35
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    Oh! Outstanding! Thank you!

    I think arvix keeps interpreting "Microscopii" as "microscope", because of the papers I get back from a search string.
    There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
    — Mark Twain, Life on the Mississippi (1883)

  6. #36
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    Quote Originally Posted by Roger E. Moore View Post
    Oh! Outstanding! Thank you!
    You're very welcome.
    I think arvix keeps interpreting "Microscopii" as "microscope", because of the papers I get back from a search string.
    I also tried a search using the star's formal IAU TLA "GAM Mic", but that didn't find anything. I wonder if there might be some older papers (pre-Hipparcos). Hmm. They'd probably use its Draper catalog number "HD 199951".

    [... searching ...]

    That search returns the following (again sorted by increasing date), although they don't actually predate Hipparcos:

    [PDF]XID: Cross-Association of ROSAT/Bright Source Catalog X-ray ...
    https://arxiv.org/pdf/astro-ph/0004053
    by RE Rutledge - ‎2000 - ‎Cited by 78 - ‎Related articles
    210117.46−321528.0. HD 199951. **. G4III. 5.543 : 4.677 ... ... ... ... 210117.46−321528.0. IRAS 20582−3227. IR ./. : 1RXSJ210139.7+680936. 0.0514 (0.0089).

    [PDF]Elemental Abundances of Solar Sibling Candidates
    https://arxiv.org/pdf/1405.1723
    by I Ramirez - ‎2014 - ‎Cited by 22 - ‎Related articles
    May 7, 2014 - at most ∼ 6300 K. HD 199951, on the other hand, appears to be a giant star of younger age than solar. All of our other targets have stellar ...

    [PDF]On the accuracy of close stellar approaches determination
    https://arxiv.org/pdf/1502.05518
    by PA Dybczyński - ‎2015 - ‎Cited by 20 - ‎Related articles
    Feb 19, 2015 - HD 199951. A. 1.18. -3.86. 2.36. -3.90 c, f. 110893. HD 239960. A. 1.92. 0.09. 1.92. 0.09 a, b, c, e, f a - Jiménez-Torres et al. (2011), b - Bobylev ...

    ETA1: That last was included in the previous list of papers.
    ETA2: Another source of references to papers about particular stars is Simbad, which claims that HD 199951 (or one of its 38 synonyms) is referenced in at least 71 papers since 1850. Scroll down to the bottom of
    http://simbad.u-strasbg.fr/simbad/si...bmit=submit+id
    Last edited by selden; 2018-Aug-03 at 02:20 PM.
    Selden

  7. #37
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    Thank you again!

    And a relevant recent paper...

    https://arxiv.org/abs/1808.00053

    Habitability in the Omega Centauri Cluster

    Stephen R. Kane, Sarah J. Deveny
    (Submitted on 31 Jul 2018)

    The search for exoplanets has encompassed a broad range of stellar environments, from single stars in the solar neighborhood to multiple stars and various open clusters. The stellar environment has a profound effect on planet formation and stability evolution and is thus a key component of exoplanetary studies. Dense stellar environments, such as those found in globular clusters, provide particularly strong constraints on sustainability of habitable planetary conditions. Here, we use Hubble Space Telescope observations of the core of the Omega Centauri cluster to derive fundamental parameters for the core stars. These parameters are used to calculate the extent of the Habitable Zone of the observed stars. We describe the distribution of Habitable Zones in the cluster and compare them with the stellar density and expected stellar encounter rate and cluster dynamics. We thus determine the effect of the stellar environment within the Omega Centauri core on the habitability of planets that reside within the cluster. Our results show that the distribution of Habitable Zone outer boundaries generally lie within 0.5 AU of the host stars, but that this small cross-sectional area is counter-balanced by a relatively high rate of stellar close encounters that would disrupt planetary orbits within the Habitable Zone of typical Omega Centauri stars.
    There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
    — Mark Twain, Life on the Mississippi (1883)

  8. #38
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    Quote Originally Posted by Tom Mazanec View Post
    Gliese 710 is now expected to miss the solar system by 13,000 AU about the year 1,352,000 AD https://en.wikipedia.org/wiki/Gliese_710
    From that link:
    "There is even a 1/10,000 chance of the star penetrating into the region (d < 1,000 AU) where the influence of the passing star on Kuiper belt objects is significant."

    Eesh!

    I wonder if Gliese 710 was what was called DM61 366 in THE STARFLIGHT HANDBOOK.

  9. 2018-Aug-05, 10:34 PM

  10. #39
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    There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
    — Mark Twain, Life on the Mississippi (1883)

  11. #40
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    https://arxiv.org/abs/1707.05277

    A catalogue of close encounter pairs

    Fabo Feng, Hugh R. A. Jones, Tabassum S. Tanvir
    (Submitted on 17 Jul 2017 (v1), last revised 21 Dec 2017 (this version, v4))

    We provide a catalogue of pairs of stars whose periapses are less than 1pc within the past or future 100 Myr. We use astrometric data from TGAS, Hipparcos and radial velocity data from RAVE and XHIP to find the space motions and hence the initial conditions of 229, 441 stars in Galactic coordinates. We simulate the orbits of these stars and focus on the time, distance and velocity at periastron for 8149 pairs using the k-d tree algorithm to find nearest neighbors. We find an anisotropy in the directions of encounter pairs caused by the solar apex motion, indicating a role of peculiar motion imposing an anisotropic tidal force on planetary systems. We call this effect "kinematic tide". Among the encounter pairs there are 4 encounters with the Solar System with periapses less than 1 pc and 96 pairs with periapses less than 0.1 pc. We also find 577 close encounters of stars which host planetary systems and/or debris disks. We discuss a range of uses for an encounter catalogue and present an example of how the time-varying network of stellar motions will be crucial for efficient interstellar travel between planetary systems.
    There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
    — Mark Twain, Life on the Mississippi (1883)

  12. #41
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    Seems to be closely related to this topic.........


    https://arxiv.org/abs/1808.05531

    Photo-evaporation of proto-planetary gas discs due to flybys of external single stars in different orbits

    Yuan-Zhe Dai, Hui-Gen Liu, Wen-bo Wu, Ji-Wei Xie, Ming Yang, Hui Zhang
    (Submitted on 16 Aug 2018)

    During the evolution of proto-planetary disc, photo-evaporations of both central and external stars play important roles. Considering the complicated radiation surroundings in the clusters, where the star formed, the proto-planetary discs survive in different lifetimes due to flyby events. In this paper, we mainly focus on the disc around a T Tauri star, which encounters with another main-sequence star with different temperatures in hyperbolic orbits with different peri-center distances, eccentricities and inclinations. We find the criterion for gap-opening due to photo-evaporation of central star after the flyby event. A gap is opened in the late stage of gas disc, and induce that the gap only influence the planet formation and migration limitedly. If the flyby orbit has a moderate value of peri-center distance, which weakly depends on the eccentricity and inclination, the external photo-evaporation lead to a maximum mass loss during the flyby event. Flyby stars in orbits with smaller eccentricities or larger inclinations induce larger mass loss. Adopting a simple multiple flyby models, we conclude that in open clusters, gas discs usually survive in typical lifetimes between 1 and 10 Myr, except there are many massive stars in dense open clusters. In globular clusters, discs disperse very quickly and hardly produce the gas giant planets. The fast-depleted discs are probably responsible for the null detection of giant planets in globular clusters.
    There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
    — Mark Twain, Life on the Mississippi (1883)

  13. #42
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    An assortment of papers, newly discovered, many under the old "Nemesis" header for this topic.


    https://arxiv.org/abs/1302.3827

    Nemesis encounters of nearby Hipparcos stars

    Igor Yu. Potemine
    (Submitted on 15 Feb 2013)

    Very close encounters of stars might lead to significant perturbations of their Oort-type clouds, planetesimal belts and planetary systems. We have calculated encounter parameters of Hipparcos stars using HIP2, Pulkovo and CRVAD2 catalogs of radial velocities. It turns out that some stars have encounters within 0.1 pc from each other and might be on an essential collision course up to few thousands AU. We present here examples with accurate astrometric data and stable with respect to errors of radial velocities within ± 0.3 km/s. They include β vs. γ Virginis, 61 Cygni vs. χ1 Orionis as well as close encounters involving η Bootis, AB Doradus, 61 Ursa Majoris and others.

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    NEMESIS: Near Encounters with M-dwarfs from an Enormous Sample and Integrated Simulations

    Bochanski, John J.; Sanderson, R. E.; West, A. A.; Burgasser, A. J.
    01/2011

    The latest spectroscopic catalog of M dwarfs identified in the Sloan Digital Sky Survey provides radial velocities, proper motions and distances for nearly 40,000 low-mass stars. Using the full 6D phase space coverage and a realistic Galactic potential, we calculated orbits for each star in the sample. The sample consists of stars from both the thin and thick disks, and the orbital properties between the two groups are compared. We also examine trends in orbital properties with spectroscopic features, such as Balmer emission and molecular bands, that should correlate with age. In addition, we have identified a number of stars that will pass very close to the Sun within the next 1000 Myrs. These stars form the "Nemesis" family of orbits. Potential encounters with these stars could have a significant impact on orbits of Oort Cloud and Kuiper Belt members as well as the planets. We comment on the probability of a catastrophic encounter within the next 1000 Myrs.

    ================================

    https://arxiv.org/abs/1007.0437

    Nemesis Reconsidered

    Adrian L. Melott (University of Kansas), Richard K. Bambach (Smithsonian Institution Museum of Natural History)
    (Submitted on 2 Jul 2010)

    The hypothesis of a companion object (Nemesis) orbiting the Sun was motivated by the claim of a terrestrial extinction periodicity, thought to be mediated by comet showers. The orbit of a distant companion to the Sun is expected to be perturbed by the Galactic tidal field and encounters with passing stars, which will induce variation in the period. We examine the evidence for the previously proposed periodicity, using two modern, greatly improved paleontological datasets of fossil biodiversity. We find that there is a narrow peak at 27 My in the cross-spectrum of extinction intensity time series between these independent datasets. This periodicity extends over a time period nearly twice that for which it was originally noted. An excess of extinction events are associated with this periodicity at 99% confidence. In this sense we confirm the originally noted feature in the time series for extinction. However, we find that it displays extremely regular timing for about 0.5 Gy. The regularity of the timing compared with earlier calculations of orbital perturbation would seem to exclude the Nemesis hypothesis as a causal factor.

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    https://arxiv.org/abs/1003.5308

    Giant Nemesis candidate HD 107914 / HIP 60503 for the perforation of Oort cloud

    Igor Yu. Potemine
    (Submitted on 27 Mar 2010)

    So far, GJ 710 is the only known star supposed to pass through outskirts of the solar system within 1 ly. We have reexamined the SIMBAD database for additional stellar candidates (from highest ratios of squared parallax to total proper motion) and compared them with new HIP2 parallaxes and known radial velocities. At the moment, the best nominee is double star HD 107914 in the constellation Centaurus at ≈ 78.3 pc from the Sun whose principal component is a white (A-type) giant. It does not seem to appear neither in general catalogues of radial velocities available at SIMBAD nor in authoritative Garcia-Sanchez et al. papers on stellar encounters with the solar system. Awaiting for the value vr of its radial velocity, uknown to the author, we have calculated limits of |vr| necessary to this star to pass within 1 ly and 1 pc from the Sun in linear approximation. A very accurate value of its total proper motion is also extremely important. In the case of vr = −100 km/s and most "advantageous" HIP2 data, HD 107914 could pass as near as 8380 AU from the Sun in an almost direct collision course with the inner part of the solar system! Inversely, if vr had a great positive value, then HIP 60503 could be the creator of peculiar trajectories of detached trans-Neptunian objects like Sedna.

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    https://arxiv.org/abs/1509.07222

    Finding the imprints of stellar encounters in long period comets

    Fabo Feng, C. A. L. Bailer-Jones
    (Submitted on 24 Sep 2015 (v1), last revised 3 Oct 2015 (this version, v2))

    The solar system's Oort cloud can be perturbed by the Galactic tide and by individual passing stars. These perturbations can inject Oort cloud objects into the inner parts of the solar system, where they may be observed as the long-period comets (periods longer than 200 years). Using dynamical simulations of the Oort cloud under the perturbing effects of the tide and 61 known stellar encounters, we investigate the link between long-period comets and encounters. We find that past encounters were responsible for injecting at least 5% of the currently known long-period comets. This is a lower limit due to the incompleteness of known encounters. Although the Galactic tide seems to play the dominant role in producing the observed long-period comets, the non-uniform longitude distribution of the cometary perihelia suggests the existence of strong -- but as yet unidentified -- stellar encounters or other impulses. The strongest individual future and past encounters are probably HIP 89825 (Gliese 710) and HIP 14473, which contribute at most 8% and 6% to the total flux of long-period comets, respectively. Our results show that the strength of an encounter can be approximated well by a simple proxy, which will be convenient for quickly identifying significant encounters in large data sets. Our analysis also indicates a smaller population of the Oort cloud than is usually assumed, which would bring the mass of the solar nebula into line with planet formation theories.

    ===================================

    https://arxiv.org/abs/1403.6633

    The secular evolution of the Kuiper belt after a close stellar encounter

    D. Punzo, R. Capuzzo-Dolcetta, S. Portegies Zwart
    (Submitted on 26 Mar 2014 (v1), last revised 27 Aug 2014 (this version, v3))

    We show the effects of the perturbation caused by a passing by star on the Kuiper belt objects (KBOs) of our Solar System. The dynamics of the Kuiper belt (KB) is followed by direct N-body simulations. The sampling of the KB has been done with N up to 131,062, setting the KBOs on initially nearly circular orbits distributed in a ring of surface density Σ∼r^−2. This modelization allowed us to investigate the secular evolution of the KB upon the encounter with the perturbing star. Actually, the encounter itself usually leads toward eccentricity and inclination distributions similar to observed ones, but tends also to excite the low-eccentricity population (e<0.1 around a ∼40 AU from the Sun), depleting this region of low eccentricities. The following long-term evolution shows a "cooling" of the eccentricities repopulating the low-eccentricity area. In dependence on the assumed KBO mass spectrum and sampled number of bodies, this repopulation takes place in a time that goes from 0.5 Myr to 100 Myr. Due to the unavoidable limitation in the number of objects in our long-term simulations (N ≤ 16384), we could not consider a detailed KBO mass spectrum, accounting for low mass objects, thus our present simulations are not reliable in constraining correlations among inclination distribution of the KBOs and other properties, such as their size distribution. However, our high precision long term simulations are a starting point for future larger studies on massively parallel computational platforms which will provide a deeper investigation of the secular evolution (∼100 Myr) of the KB over its whole mass spectrum.
    There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
    — Mark Twain, Life on the Mississippi (1883)

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    https://arxiv.org/abs/1004.1557

    Transit of Luyten 726-8 within 1 ly from Epsilon Eridani

    Igor Yu. Potemine
    (Submitted on 9 Apr 2010)

    This is one of results from our program of massive simulations of close encounters for all nearby stars. Epsilon Eridani is an extremely interesting star having one confirmed planet and multiple asteroid and debris belts. It should have a quite massive Oort cloud as well. Deltorn et al. searched for past Nemesis encounters of ε Eri. In this paper we show that, according to current astrometric data, an other famous nearby star Luyten 726-8AB (=BL/UV Ceti) will pass at ≲ 0.93 ly from Epsilon Eridani in ≈ 31.5 kyr. So, it will probably pierce through the outer part of the hypothetical Oort cloud of ϵ Eri. BL/UV Ceti has only about 20 percent of the solar mass. Nevertheless, it could influence directly some long-period comets of Epsilon Eridani. The duration of mutual transit of two star systems within 1 ly from each other is ≳ 4.6 kyr. Our simulations show that stellar encounters within 1 ly might be more frequent than previously thought. It could explain Proxima's peculiar trajectory with respect to α Cen AB or even Sedna's trajectory in the solar system.

    ========================

    https://arxiv.org/abs/astro-ph/0105284

    Search for Nemesis Encounters with Vega, epsilon Eridani, and Fomalhaut

    J.-M. Deltorn (Space Telescope Science Institute), P. Kalas (University of California, Berkeley)
    (Submitted on 16 May 2001)

    We calculate the space motions of 21,497 stars to search for close stellar encounters with Vega, epsilon Eridani and Fomalhaut during the past 1 Myr. We discover that epsilon Eridani experienced three <2 pc encounters over the past 100,000 yr. Within the uncertainties, epsilon Eridani is having a close encounter with Kapteyn's star near the present epoch, with a 42.2 percent probability that the closest approach distance is <1 pc. Vega and Fomalhaut experienced four and six <2 pc encounters, respectively, over the past 1 Myr. Each had one encounter with a roughly 2 percent probability that the closest approach distance is less than 0.5 pc. These encounters will not directly influence the debris disks observed around Vega, epsilon Eridani and Fomalhaut, but they may pass through hypothetical Oort clouds surrounding these stars. We find that two other Vega-like stars, HD 17848 and HD 20010, experienced rare, <0.1 pc stellar encounters that are more likely to directly perturb their circumstellar disks.

    ======================================

    https://arxiv.org/abs/astro-ph/0011279

    Close stellar encounters with planetesimal discs: The dynamics of asymmetry in the Beta Pictoris system

    J.D. Larwood (Univ. of London), P.G. Kalas (UC Berkeley)
    (Submitted on 14 Nov 2000)

    We numerically investigate the dynamics of how a close stellar fly-by encounter of a symmetrical circumstellar planetesimal disc can give rise to the many kinds of asymmetries and substructures attributed to the edge-on dusty disc of Beta Pic. In addition we present new optical coronagraphic observations of the outer parts of Beta Pic's disc, and report that the radial extent is significantly greater than was found in previous measurements. The northeasterly extension of the disc's midplane is now measured out to 1835au from the star; the southwesterly component is measured out to 1450au. Hence we use the length asymmetry induced in a distribution of simulation test particles as the principal diagnostic feature when modelling the disc response, in order to constrain fly-by parameters. In particular we favour a low inclination prograde and near-parabolic orbit perturber of mass approximately 0.5 Solar masses. These initial conditions suggest that the perturber could have been physically associated with Beta Pic prior to the encounter. Thus we also consider the possibility that the perturber could be bound to Beta Pic: a consideration also of general interest where dust discs are known to exist in binary star systems. In some of our models, we can relate groupings of perturbed particles to the large-scale structure of the Beta Pic disc. The groupings correspond to: high eccentricity and inclination particles that reach apocentre and maximum height in the southwest, moderately eccentric and low inclination particles that reach apocentre in the northeast, and relatively unperturbed particles inside approximately 200au radius.
    There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
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