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The Discovery of Exoplanets
L'Univers, S´eminairePoincar´eXX (2015) 113 { 137 S´eminairePoincar´e New Worlds Ahead: The Discovery of Exoplanets Arnaud Cassan Universit´ePierre et Marie Curie Institut d'Astrophysique de Paris 98bis boulevard Arago 75014 Paris, France Abstract. Exoplanets are planets orbiting stars other than the Sun. In 1995, the discovery of the first exoplanet orbiting a solar-type star paved the way to an exoplanet detection rush, which revealed an astonishing diversity of possible worlds. These detections led us to completely renew planet formation and evolu- tion theories. Several detection techniques have revealed a wealth of surprising properties characterizing exoplanets that are not found in our own planetary system. After two decades of exoplanet search, these new worlds are found to be ubiquitous throughout the Milky Way. A positive sign that life has developed elsewhere than on Earth? 1 The Solar system paradigm: the end of certainties Looking at the Solar system, striking facts appear clearly: all seven planets orbit in the same plane (the ecliptic), all have almost circular orbits, the Sun rotation is perpendicular to this plane, and the direction of the Sun rotation is the same as the planets revolution around the Sun. These observations gave birth to the Solar nebula theory, which was proposed by Kant and Laplace more that two hundred years ago, but, although correct, it has been for decades the subject of many debates. In this theory, the Solar system was formed by the collapse of an approximately spheric giant interstellar cloud of gas and dust, which eventually flattened in the plane perpendicular to its initial rotation axis. -
Black-Hole Binaries, Gravitational Waves, and Numerical Relativity
Black-hole binaries, gravitational waves, and numerical relativity Joan Centrella∗ and John G. Baker† Gravitational Astrophysics Laboratory, NASA/GSFC, 8800 Greenbelt Road, Greenbelt, Maryland 20771, USA Bernard J. Kelly‡ and James R. van Meter§ CRESST and Gravitational Astrophysics Laboratory, NASA/GSFC, 8800 Greenbelt Road, Greenbelt, Maryland 20771, USA and Department of Physics, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250, USA (Dated: November 30, 2010) Understanding the predictions of general relativity for the dynamical interactions of two black holes has been a long-standing unsolved problem in theoretical physics. Black-hole mergers are monu- mental astrophysical events, releasing tremendous amounts of energy in the form of gravitational radiation, and are key sources for both ground- and space-based gravitational-wave detectors. The black-hole merger dynamics and the resulting gravitational waveforms can only be calculated through numerical simulations of Einstein’s equations of general relativity. For many years, nu- merical relativists attempting to model these mergers encountered a host of problems, causing their codes to crash after just a fraction of a binary orbit could be simulated. Recently, however, a series of dramatic advances in numerical relativity has allowed stable, robust black-hole merger simulations. This remarkable progress in the rapidly maturing field of numerical relativity, and the new understanding of black-hole binary dynamics that is emerging is chronicled. Important applications of these fundamental physics results to astrophysics, to gravitational-wave astronomy, and in other areas are also discussed. Contents G. Numerical Approximation Methods 15 H. Extracting the Physics 15 I. Prelude 2 V. Black-Hole Merger Dynamics and Waveforms 16 II. -
Are Gamma-Ray Bursts Signals of Supermassive Black Hole Formation?
Are Gamma-Ray Bursts Signals of Supermassive Black Hole Formation? K. Abazajian, G. Fuller, X. Shi Department of Physics, University of California, San Diego, La Jolla, California 92093-0350 Abstract. The formation of supermassive black holes through the gravitational 4 collapse of supermassive objects (M ∼> 5 × 10 M⊙) has been proposed as a source of cosmological γ-ray bursts. The major advantage of this model is that such collapses are far more energetic than stellar-remnant mergers. The major drawback of this idea is the severe baryon loading problem in one-dimensional models. We can show that the observed log N − log P (number vs. peak flux) distribution for gamma-ray bursts in the BATSE database is not inconsistent with an identification of supermassive object collapse as the origin of the gamma-ray bursts. This conclusion is valid for a range of plausible cosmological and γ-ray burst spectral parameters. 1. Introduction We investigate aspects of a recent model for the internal engine powering γ-ray bursts (GRBs). This model produces a GRB fireball through neutrino emission and annihilation during the collapse of a supermassive object into a black hole (Fuller & Shi, 1998). This supermassive object may either be a relativistic cluster of stars or a single supermassive star. The collapse of a supermassive object provides an exceedingly large amount of energy to power the burst, much higher than the amount of energy available in stellar remnant models. In addition, the rate of collapse of these objects–when associated with galaxy-type structures–is arXiv:astro-ph/9812287v1 15 Dec 1998 similar to the GRB rate. -
Ocular Surface Changes Associated with Ophthalmic Surgery
Journal of Clinical Medicine Review Ocular Surface Changes Associated with Ophthalmic Surgery Lina Mikalauskiene 1, Andrzej Grzybowski 2,3 and Reda Zemaitiene 1,* 1 Department of Ophthalmology, Medical Academy, Lithuanian University of Health Sciences, 44037 Kaunas, Lithuania; [email protected] 2 Department of Ophthalmology, University of Warmia and Mazury, 10719 Olsztyn, Poland; [email protected] 3 Institute for Research in Ophthalmology, Foundation for Ophthalmology Development, 61553 Poznan, Poland * Correspondence: [email protected] Abstract: Dry eye disease causes ocular discomfort and visual disturbances. Older adults are at a higher risk of developing dry eye disease as well as needing for ophthalmic surgery. Anterior segment surgery may induce or worsen existing dry eye symptoms usually for a short-term period. Despite good visual outcomes, ocular surface dysfunction can significantly affect quality of life and, therefore, lower a patient’s satisfaction with ophthalmic surgery. Preoperative dry eye disease, factors during surgery and postoperative treatment may all contribute to ocular surface dysfunction and its severity. We reviewed relevant articles from 2010 through to 2021 using keywords “cataract surgery”, ”phacoemulsification”, ”refractive surgery”, ”trabeculectomy”, ”vitrectomy” in combina- tion with ”ocular surface dysfunction”, “dry eye disease”, and analyzed studies on dry eye disease pathophysiology and the impact of anterior segment surgery on the ocular surface. Keywords: dry eye disease; ocular surface dysfunction; cataract surgery; phacoemulsification; refractive surgery; trabeculectomy; vitrectomy Citation: Mikalauskiene, L.; Grzybowski, A.; Zemaitiene, R. Ocular Surface Changes Associated with Ophthalmic Surgery. J. Clin. 1. Introduction Med. 2021, 10, 1642. https://doi.org/ 10.3390/jcm10081642 Dry eye disease (DED) is a common condition, which usually causes discomfort, but it can also be an origin of ocular pain and visual disturbances. -
Gamma Ray Bursts from Stellar Collisions
CORE Metadata, citation and similar papers at core.ac.uk Provided by CERN Document Server Gamma Ray Bursts from Stellar Collisions Brad M.S. Hansen & Chigurupati Murali Canadian Institute for Theoretical Astrophysics University of Toronto, Toronto, ON M5S 3H8, Canada Received ; accepted –2– ABSTRACT We propose that the cosmological gamma ray bursts arise from the collapse of neutron stars to black holes triggered by collisions or mergers with main sequence stars. This scenario represents a cosmological history qualitatively different from most previous theories because it contains a significant contribution from an old stellar population, namely the globular clusters. Furthermore, the gas poor central regions of globular clusters provide an ideal environment for the generation of the recently confirmed afterglows via the fireball scenario. Collisions resulting from neutron star birth kicks in close binaries may also contribute to the overall rate and should lead to associations between some gamma ray bursts and supernovae of type Ib/c. Subject headings: stars:neutron–supernovae:general–globular clusters:general– gamma rays:bursts– Galaxy:evolution –3– 1. Introduction The detection of X-ray, optical and radio afterglows from gamma-ray burst events (Costa et al 1997; van Paradijs et al 1997, Sahu et al 1997; Frail et al 1997) and concommitant redshifts (Metzger et al 1997) has provided strong support for the cosmological origin of the phenomenon. The success of the fireball model (Cavallo & Rees 1978; Rees & Meszaros 1992; Meszaros & Rees 1993) is largely independent of the origin of the energy, requiring only an energetic and baryon-poor event confined to small scales, thereby giving rise to a relativistic and optically thick outflow. -
Formation of Moon Systems Around Giant Planets Capture and Ablation of Planetesimals As Foundation for a Pebble Accretion Scenario T
A&A 633, A93 (2020) Astronomy https://doi.org/10.1051/0004-6361/201936804 & © ESO 2020 Astrophysics Formation of moon systems around giant planets Capture and ablation of planetesimals as foundation for a pebble accretion scenario T. Ronnet and A. Johansen Department of Astronomy and Theoretical Physics, Lund Observatory, Lund University, Box 43, 22100 Lund, Sweden e-mail: [email protected] Received 28 September 2019 / Accepted 10 December 2019 ABSTRACT The four major satellites of Jupiter, known as the Galilean moons, and Saturn’s most massive satellite, Titan, are believed to have formed in a predominantly gaseous circum-planetary disk during the last stages of formation of their parent planet. Pebbles from the protoplanetary disk are blocked from flowing into the circumplanetary disk by the positive pressure gradient at the outer edge of the planetary gap, so the gas drag assisted capture of planetesimals should be the main contributor to the delivery of solids onto circum- planetary disks. However, a consistent framework for the subsequent accretion of the moons remains to be built. Here, we use numerical integrations to show that most planetesimals that are captured within a circum-planetary disk are strongly ablated due to the frictional heating they experience, thus supplying the disk with small dust grains, whereas only a small fraction “survives” their capture. We then constructed a simple model of a circum-planetary disk supplied by ablation, where the flux of solids through the disk is at equilibrium with the ablation supply rate, and we investigate the formation of moons in such disks. We show that the growth of satellites is mainly driven by accretion of the pebbles that coagulate from the ablated material. -
Potential of Laser-Induced Ablation for Future Space Applications
Space Policy 28 (2012) 149e153 Contents lists available at SciVerse ScienceDirect Space Policy journal homepage: www.elsevier.com/locate/spacepol Viewpoint Potential of laser-induced ablation for future space applications Alison Gibbings a,c,*, Massimiliano Vasile a, John-Mark Hopkins b, David Burns b, Ian Watson c a Advanced Space Concepts Laboratory, Department of Mechanical and Aerospace Engineering, University of Strathclyde, 75 Montrose Street, Glasgow G1 1X1, UK b Institute of Photonics, University of Strathclyde, Wolfson Centre, 106 Rottenrow, Glasgow, UK c Systems, Power and Energy Research Division, University of Glasgow, School of Engineering, James Watt (South) Building, University of Glasgow, University Avenue, Glasgow, UK article info abstract Article history: This paper surveys recent and current advancements of laser-induced ablation technology for space- Received 24 February 2012 based applications and discusses ways of bringing such applications to fruition. Laser ablation is ach- Received in revised form ieved by illuminating a given material with a laser light source. The high surface power densities 21 May 2012 provided by the laser enable the illuminated material to sublimate and ablate. Possible applications Accepted 22 May 2012 include the deflection of Near Earth Objects e asteroids and comets e from an Earth-impacting event, Available online 16 June 2012 the vaporisation of space structures and debris, the mineral and material extraction of asteroids and/or as an energy source for future propulsion systems. This paper will discuss each application and the tech- nological advancements that are required to make laser-induced ablation a practical process for use within the space arena. Particular improvements include the efficiency of high power lasers, the colli- mation of the laser beam (including beam quality) and the power conversion process. -
Formation of Redback Pulsars
Formation of Redback Pulsars Sarah L. Smedley 10th June 2015 Supervisor: Chris Tout Collaborators: Lilia Ferrario and Dayal Wickramasinghe Talk outline Define redbacks (RBs). Describe the current RB population. Introduce our possible formation pathway for RBs which includes the accretion-induced collapse of an ONeMg white dwarf. Show the results of modelling this formation pathway with the Cambridge STARS code. Draw conclusions on the viability of this formation pathway. Millisecond Pulsars (MSPs) magnetic spin axis axis P < 30ms spin Weaker magnetic fields NS Typically Old Binary What is a Redback Pulsar? A redback pulsar is a millisecond pulsar with a non-degenerate companion. The radio signal of a RB is eclipsed for a large portion of the orbit which suggests the companion is ablated. Ablated Companion Radio MSP There are 16 RBs known. Most of them were found in follow up surveys of gamma-ray sources. They have circular orbits. Observed redback population Median masses of companions of known RBs with main-sequence companions. Median mass of companion to PSR J1816+4510. Median masses of companions for known RBs with unknown companions. Binary mass fuction calculated from measurement of the doppler shift of the pulsar and the orbital period. 3 And BMF = (Mc sin i) 2 (MNS + Mc) Minimum comp. mass: i = 90 degrees. Median comp. mass: i = 60 degrees. Upper comp. mass: i = 25.8 degrees. MNS = 1.25 M for post-AIC NS mass. Observed redback population Median masses of companions of known RBs with main-sequence companions. Median mass of companion to PSR J1816+4510. Median masses of companions for known RBs with unknown companions. -
NEW ACTIVE REMOTE-SENSING CAPABILITIES: LASER ABLATION SPECTROMETER and LIDAR ATMOSPHERIC SPECIES PROFILE MEASUREMENTS. R. J. De Young and J
Lunar and Planetary Science XXXVI (2005) 1196.pdf NEW ACTIVE REMOTE-SENSING CAPABILITIES: LASER ABLATION SPECTROMETER AND LIDAR ATMOSPHERIC SPECIES PROFILE MEASUREMENTS. R. J. De Young and J. T. Bergstralh, Science Directorate, NASA Langley Research Center, MS 401A, Hampton, VA 23681, [email protected], [email protected] Introduction: With the quality (M2 = 1.5). As tested, this anticipated development of high- system occupies a volume of 114 x 152 capacity fission power and electric x 45 cm, but it could be made propulsion for deep-space missions, it substantially smaller for space will become possible to propose applications. This laser could be the experiments that demand higher power pump source for the following than current technologies (e.g. instruments. radioisotope power sources) provide. Laser Ablation Mass Jupiter Icy Moons Orbiter (JIMO), the Spectrometer: High-energy pulses from first mission in the Project Prometheus the Yb:YAG laser, focused by a 2 meter program, will explore the icy moons of diameter transmission mirror, would Jupiter with a suite of high-capability produce energy densities of the order of experiments that take advantage of the 109 Watts cm-2 on a surface at a distance high power levels (and indirectly, the of 100 km. The resulting plasma would high data rates) that fission power generate ions of sufficient energy and affords. This abstract describes two quantity to be detected with a mass high-capability active-remote-sensing spectrometer on the spacecraft [1,2]. experiments that will be logical This would make it possible to map with candidates for subsequent Prometheus- very high spatial resolution the class missions. -
Volume Estimation of Excimer Laser Tissue Ablation for Correction of Spherical Myopia and Hyperopia
Volume Estimation of Excimer Laser Tissue Ablation for Correction of Spherical Myopia and Hyperopia Damien Gatinel,1 Thanh Hoang-Xuan,1 and Dimitri T. Azar1,2 PURPOSE. To determine the theoretical volumes of ablation for stromal bed have been implicated as determinants of corneal the laser treatment of spherical refractive errors in myopia and stability, further studies are necessary to evaluate their exact hyperopia. significance. New models estimating the volume of the corneal METHODS. The cornea was modeled as a spherical shell. The tissue ablated by a laser refractive procedure may also be ablation profiles for myopia and hyperopia were based on an necessary to determine the influence of ablated volumes on established paraxial formula. The theoretical volumes of the corneal stability and the procedure’s outcome. ablated corneal lenticules for the correction of myopia and The primary focus of this work is to provide a formula to hyperopia were calculated by two methods: (1) mathematical approximate the volume of tissue ablation for spherical cor- approximation based on a simplified geometric model and (2) rection in myopia and hyperopia. In this study, we approached finite integration. These results were then compared for opti- the volume calculation by two approaches: finite integration cal zone diameters of 0.5 to 11.00 mm and for initial radii of and mathematical approximation. We compared the theoreti- curvature of 7.5, 7.8, and 8.1 mm. cal values of volumes of tissue removal in the treatment of spherical refractive errors predicted by our geometric approx- RESULTS. Referring to a simplified geometrical model, the vol- imation with the values given by finite integration. -
Formation of Moon Systems Around Giant Planets: Capture and Ablation of Planetesimals As Foundation for a Pebble Accretion Scenario
Astronomy & Astrophysics manuscript no. draft c ESO 2019 December 11, 2019 Formation of moon systems around giant planets Capture and ablation of planetesimals as foundation for a pebble accretion scenario T. Ronnet and A. Johansen Department of Astronomy and Theoretical Physics, Lund Observatory, Lund University, Box 43, 22100 Lund, Sweden e-mail: [email protected] Received ; accepted ABSTRACT The four major satellites of Jupiter, known as the Galilean moons, and Saturn’s most massive satellite, Titan, are believed to have formed in a predominantly gaseous circum-planetary disk, during the last stages of formation of their parent planet. Pebbles from the protoplanetary disk are blocked from flowing into the circumplanetary disk by the positive pressure gradient at the outer edge of the planetary gap, so the gas drag assisted capture of planetesimals should be the main contributor to the delivery of solids onto circum-planetary disks. However, a consistent framework for the subsequent accretion of the moons remains to be built. Here we use numerical integrations to show that most planetesimals being captured within a circum-planetary disk are strongly ablated due to the frictional heating they experience, thus supplying the disk with small dust grains, whereas only a small fraction ’survives’ their capture. We then construct a simple model of a circum-planetary disk supplied by ablation, where the flux of solids through the disk is at equilibrium with the ablation supply rate, and investigate the formation of moons in such disks. We show that the growth of satellites is driven mainly by accretion of the pebbles that coagulate from the ablated material. -
On the Habitability of Our Universe
Chapter for the book Consolidation of Fine Tuning On the Habitability of Our Universe Abraham Loeb Astronomy department, Harvard University, 60 Garden Street, Cambridge, MA 02138, USA E-mail: [email protected] Abstract. Is life most likely to emerge at the present cosmic time near a star like the Sun? We consider the habitability of the Universe throughout cosmic history, and conservatively restrict our attention to the context of “life as we know it” and the standard cosmological model, ΛCDM. The habitable cosmic epoch started shortly after the first stars formed, about 30 Myr after the Big Bang, and will end about 10 Tyr from now, when all stars will die. We review the formation history of habitable planets and find that unless habitability around low mass stars is suppressed, life is most likely to exist near ∼ 0.1M stars ten trillion years from now. Spectroscopic searches for biosignatures in the atmospheres of transiting Earth-mass planets around low mass stars will determine whether present-day life is indeed premature or typical from a cosmic perspective. arXiv:1606.08926v2 [astro-ph.CO] 24 Nov 2016 Contents 1 Introduction2 2 The Habitable Epoch of the Early Universe4 2.1 Section Background4 2.2 First Planets4 2.3 Section Summary and Implications5 3 CEMP Stars: Possible Hosts to Carbon Planets in the Early Universe6 3.1 Section Background6 3.2 Star-forming environment of CEMP stars7 3.3 Orbital Radii of Potential Carbon Planets9 3.4 Mass-Radius Relationship for Carbon Planets 13 3.5 Section Summary and Implications 15 4 Water