Universes Without the Weak Force: Astrophysical Processes with Stable Neutrons
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Concepts for a Deuterium-Deuterium Fusion Reactor
Concepts for a deuterium-deuterium fusion reactor Roberto Onofrio1, 2 1Dipartimento di Fisica e Astronomia “Galileo Galilei”, Universit`adi Padova, Via Marzolo 8, Padova 35131, Italy 2Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755, USA We revisit the assumption that reactors based on deuterium-deuterium (D-D) fusion processes have to be necessarily developed after the successful completion of experiments and demonstrations for deuterium-tritium (D-T) fusion reactors. Two possible mechanisms for enhancing the reactivity are discussed. Hard tails in the energy distribution of the nuclei, through the so-called κ-distribution, allow to boost the number of energetic nuclei available for fusion reactions. At higher temperatures − − than usually considered in D-T plasmas, vacuum polarization effects from real e+e and µ+µ pairs may provide further speed-up due to their contribution to screening of the Coulomb barrier. Furthermore, the energy collection system can benefit from the absence of the lithium blanket, both in simplicity and compactness. The usual thermal cycle can be bypassed with comparable efficiency levels using hadronic calorimetry and third-generation photovoltaic cells, possibly allowing to extend the use of fusion reactors to broader contexts, most notably maritime transport. I. INTRODUCTION high yield scintillating materials and hadronic calorime- try with third-generation photovoltaic cells. This could lead to energy conversion at an initially nearly compara- It is usually assumed that the first commercial fusion ble efficiency with respect to a thermal cycle, with un- reactors will be based on D-T mixtures, and within this known margins for improvement, and within a compact frame a well-defined path has been paved with the ongo- design. -
A Stripped Helium Star in the Potential Black Hole Binary LB-1 A
A&A 633, L5 (2020) Astronomy https://doi.org/10.1051/0004-6361/201937343 & c ESO 2020 Astrophysics LETTER TO THE EDITOR A stripped helium star in the potential black hole binary LB-1 A. Irrgang1, S. Geier2, S. Kreuzer1, I. Pelisoli2, and U. Heber1 1 Dr. Karl Remeis-Observatory & ECAP, Astronomical Institute, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Sternwartstr. 7, 96049 Bamberg, Germany e-mail: [email protected] 2 Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany Received 18 December 2019 / Accepted 1 January 2020 ABSTRACT +11 Context. The recently claimed discovery of a massive (MBH = 68−13 M ) black hole in the Galactic solar neighborhood has led to controversial discussions because it severely challenges our current view of stellar evolution. Aims. A crucial aspect for the determination of the mass of the unseen black hole is the precise nature of its visible companion, the B-type star LS V+22 25. Because stars of different mass can exhibit B-type spectra during the course of their evolution, it is essential to obtain a comprehensive picture of the star to unravel its nature and, thus, its mass. Methods. To this end, we study the spectral energy distribution of LS V+22 25 and perform a quantitative spectroscopic analysis that includes the determination of chemical abundances for He, C, N, O, Ne, Mg, Al, Si, S, Ar, and Fe. Results. Our analysis clearly shows that LS V+22 25 is not an ordinary main sequence B-type star. The derived abundance pattern exhibits heavy imprints of the CNO bi-cycle of hydrogen burning, that is, He and N are strongly enriched at the expense of C and O. -
Evolution of Helium Star Plus Carbon-Oxygen White Dwarf Binary Systems and Implications for Diverse Stellar Transients and Hypervelocity Stars
A&A 627, A14 (2019) https://doi.org/10.1051/0004-6361/201935322 Astronomy c ESO 2019 & Astrophysics Evolution of helium star plus carbon-oxygen white dwarf binary systems and implications for diverse stellar transients and hypervelocity stars P. Neunteufel1, S.-C. Yoon2, and N. Langer1 1 Argelander Institut für Astronomy (AIfA), University of Bonn, Auf dem Hügel 71, 53121 Bonn, Germany e-mail: [email protected] 2 Department of Physics and Astronomy, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea Received 20 February 2019 / Accepted 28 April 2019 ABSTRACT Context. Helium accretion induced explosions in CO white dwarfs (WDs) are considered promising candidates for a number of observed types of stellar transients, including supernovae (SNe) of Type Ia and Type Iax. However, a clear favorite outcome has not yet emerged. Aims. We explore the conditions of helium ignition in the WD and the final fates of helium star-WD binaries as functions of their initial orbital periods and component masses. Methods. We computed 274 model binary systems with the Binary Evolution Code, in which both components are fully resolved. Both stellar and orbital evolution were computed including mass and angular momentum transfer, tides, gravitational wave emission, differential rotation, and internal hydrodynamic and magnetic angular momentum transport. We worked out the parts of the parameter space leading to detonations of the accreted helium layer on the WD, likely resulting in the complete disruption of the WD to deflagrations, where the CO core of the WD may remain intact and where helium ignition in the WD is avoided. -
Lecture 7 Evolution of Massive Stars on the Main Sequence and During
Massive Stars Generalities: Because of the general tendency of the interior temperature of main sequence stars to increase with mass*, stars of over two Lecture 7 solar mass are chiefly powered by the CNO cycle(s) rather than the pp cycle(s). The high temperature sensitivity of the CNO cycle (n = 17 instead of 4 for pp-cycle) makes the energy Evolution of Massive generation very centrally concentrated. This, plus the increasing Stars on the Main Sequence fraction of pressure due to radiation, makes their cores convective. Because of the greater temperature, the opacity in and During Helium Burning - their interiors is dominantly due to electron scattering. Basics Despite their convective cores, the overall main sequence structure can be crudely represented as an n = 3 polytrope. This is especially true of the outer radiative part of the star that typically includes the majority of the mass. * To provide a luminosity that increases as M3 s15 3233 2.19951015502790E+14 c12( 1)= 7.5000E+10 R = 4.3561E+11 Teff = 2.9729E+04 L = 1.0560E+38 Iter = 37 Zb = 61 inv = 66 Dc = 5.9847E+00 Tc = 3.5466E+07 Ln = 6.9735E+36 Jm = 1048 Etot = -9.741E+49 B star 10,000 – 30,000 K 1 HHHHH 15 Solar mass He He HeH Convective history HH He He He He He .1 15 M half way ⊙ through hydrogen burning Elemental Mass Fraction .01 N N N O OOOO N C C N C Fe Fe Fe Fe Fe Fe Fe Fe IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIINeIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII NeIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII!,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, Ne,,I,,,,,,,,,,Ii,,,,,,,,,,,,,,,,,,,,,,,,,I,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, Ne,,,,,,,,,,,,........................................................................................................... -
Can Deuterium Formation Be Measured?
CAN DEUTERIUM FORMATION BE MEASURED? Robert K. Soberman∗ and Maurice Dubin† retired (Dated: November 12, 2018) The fundamental PP reaction has never been attempted in the laboratory as theory states it cannot be measured within the human life span. This forms the foundation of stellar nucleosynthesis and the standard solar model. Yet numerous observations including the Sun’s obvious variability argue the theory is flawed and the reaction occurs in times many orders of magnitude shorter than prediction. Considering the consequence to accepted models and controlled fusion, testing is warranted. PACS numbers: 95.30.Cq, 96.60.-j, 25.40.-h There is no record of an attempt to measure the transmutation probability for the fundamental reaction 1H(p, e+,ν)2H. As Bethe and Critchfield [1] predicted a reaction rate of 14(10)9 years no one has been bold enough to test this prediction. Parker and Rolfs [2] wrote “It can be estimated that with a total cross section of 10−47cm2 at Ep(lab) = 1MeV for a proton beam of 1 mA incident on a thick hydrogen target, there would be only one 1H(p, e+,ν)2H reaction in 106 yr.” A similar but numerically discrepant statement appears in Clayton’s classic stellar nucleosynthesis text [3]. As no research team has the patients, resources or longevity to wait out such a prediction it is not surprising that it has never been tested. Such a slow reaction rate was necessary for the standard stellar power model. A much shorter time would cut the lifetime of stars accordingly and a brief reaction time such as seconds would, in that model, cause stars to explode when the reaction conditions were reached. -
Cold Fusion Phenomena May 23-25, 1989 Santa Fe, New Mexico
WORKSHOP ON COLD FUSION PHENOMENA MAY 23-25, 1989 SANTA FE, NEW MEXICO AGENDA Sponsored by Los Alamos National Laboratory and the U.S. Department of Energy TABLE OF CONTENTS Program Committee V Agenda 1-6 Abstracts of Presentations Sessions A - E WORKSHOP CO-CHAIRMAN Prof. Johann Rafelski Department of Physics Dr. Norman Hackerman University of Arizona The Welch Foundation Tucson, AZ Houston, TX Dr. A. John Appleby Dr. J. Robert Schrieffer Center for Electrochemical Systems Director, Institute for and Hydrogen Research Theoretical Physics Texas A&M University University of California College Station, TX Santa Barbara, CA Dr. Anthony L. Turkevich Enrico Fermi Institute TECHNICAL PROGRAM COORDINATOR University of Chicago Chicago, IL Dr. Reed J. Jensen Los Alamos National Laboratory PROGRAM SUPPORT COORDINATOR Mr. David C. Phillips Los Alamos National Laboratory WORKSHOP PROGRAM COMMITTEE Prof. Allen Bard Department of Chemistry University of Texas Austin, TX Dr. Hans Frauenfelder Department of Physics University of Illinois at Urbana-Champaign Urbana, IL Dr. Steven E. Jones Department of Chemistry Brigham Young University Provo, UT Prof. Arthur K. Kerman Director, Laboratory for Nuclear Science MIT Cambridge, MA Prof. Steve Koonin Institute for Theoretical Physics University of California Santa Barbara, CA AGENDA WORKSHOP ON COLD FUSION PHENOMENA May 22-25, 1989 SWEENEY CENTER, SANTA FE, NM MONDAY, MAY 22 Workshop participants arrive in Santa Fe 4:00 - 8:00 Registration and badge issue at EldoradoHotel -Hospitality room available at EldoradoHotel TUESDAY, MAY 23 7:30 - 8:00 Arrival at Sweeney Center 8:00 - 8:30 Late Registration 8:30 - 9:00 Preliminary Remarks Reed J. -
Stellar Evolution
AccessScience from McGraw-Hill Education Page 1 of 19 www.accessscience.com Stellar evolution Contributed by: James B. Kaler Publication year: 2014 The large-scale, systematic, and irreversible changes over time of the structure and composition of a star. Types of stars Dozens of different types of stars populate the Milky Way Galaxy. The most common are main-sequence dwarfs like the Sun that fuse hydrogen into helium within their cores (the core of the Sun occupies about half its mass). Dwarfs run the full gamut of stellar masses, from perhaps as much as 200 solar masses (200 M,⊙) down to the minimum of 0.075 solar mass (beneath which the full proton-proton chain does not operate). They occupy the spectral sequence from class O (maximum effective temperature nearly 50,000 K or 90,000◦F, maximum luminosity 5 × 10,6 solar), through classes B, A, F, G, K, and M, to the new class L (2400 K or 3860◦F and under, typical luminosity below 10,−4 solar). Within the main sequence, they break into two broad groups, those under 1.3 solar masses (class F5), whose luminosities derive from the proton-proton chain, and higher-mass stars that are supported principally by the carbon cycle. Below the end of the main sequence (masses less than 0.075 M,⊙) lie the brown dwarfs that occupy half of class L and all of class T (the latter under 1400 K or 2060◦F). These shine both from gravitational energy and from fusion of their natural deuterium. Their low-mass limit is unknown. -
Primordial Nucleosynthesis in the Precision Cosmology Era the Annual Review of Nuclear and Particle Science Gary Steigman (2007)
Primordial Nucleosynthesis in the Precision Cosmology Era The Annual Review of Nuclear and Particle Science Gary Steigman (2007) Galactic Archeology Seminar Manuel Kramer Universit¨atHeidelberg December 1, 2017 Contents 1 Introduction 2 Fusion of the first nuclides 3 Observations of the relic nuclides 4 Theory vs data 5 Summary Source: CERN Introduction Fusion of the first nuclides Observations of the relic nuclides Theory vs data Summary Fusion of the first nuclides Initial neutron to proton ratio Neutron & Proton equilibrium Once stable hadrons can form from the quark gluon plasma in the very early universe, neutrons and protons are in thermal equilibrium by the weak interactions: − p + e $ n + νe (1) + n + e $ p +ν ¯e Mass of protons is slightly lower than that of the neutrons ni =pi = 1=7 (2) Introduction Fusion of the first nuclides Observations of the relic nuclides Theory vs data Summary Deuterium evolution Deuterium is formed by fusion of a proton and a neutron n + p $ d + γ (3) Significant amounts can only built up when kT . 80 keV −10 The higher the baryon density η10 = 10 (nB=nγ), the higher the interaction rate Introduction Fusion of the first nuclides Observations of the relic nuclides Theory vs data Summary Helium-4 evolution Nucelar fusion processes The starting point for all subsequent fusions is Deuterium Deuterium fusion is a slow reaction Deuterium is immediately converted to 3He and tritium no stable mass-5 nuclides ! bottleneck at 4He Source: https://en.wikipedia.org/ wiki/Big Bang nucleosynthesis Introduction Fusion of -
Modern Physics, the Nature of the Interaction Between Particles Is Carried a Step Further
44.1 Some Properties of Nuclei 1385 are the same, apart from the additional repulsive Coulomb force for the proton– U(r ) (MeV) proton interaction. 40 Evidence for the limited range of nuclear forces comes from scattering experi- n–p system ments and from studies of nuclear binding energies. The short range of the nuclear 20 force is shown in the neutron–proton (n–p) potential energy plot of Figure 44.3a 0 r (fm) obtained by scattering neutrons from a target containing hydrogen. The depth of 1 567432 8 the n–p potential energy well is 40 to 50 MeV, and there is a strong repulsive com- Ϫ20 ponent that prevents the nucleons from approaching much closer than 0.4 fm. Ϫ40 The nuclear force does not affect electrons, enabling energetic electrons to serve as point-like probes of nuclei. The charge independence of the nuclear force also Ϫ60 means that the main difference between the n–p and p–p interactions is that the a p–p potential energy consists of a superposition of nuclear and Coulomb interactions as shown in Figure 44.3b. At distances less than 2 fm, both p–p and n–p potential The difference in the two curves energies are nearly identical, but for distances of 2 fm or greater, the p–p potential is due to the large Coulomb has a positive energy barrier with a maximum at 4 fm. repulsion in the case of the proton–proton interaction. The existence of the nuclear force results in approximately 270 stable nuclei; hundreds of other nuclei have been observed, but they are unstable. -
Variable Star
Variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) fluctuates. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as either: Intrinsic variables, whose luminosity actually changes; for example, because the star periodically swells and shrinks. Extrinsic variables, whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth; for example, because the star has an orbiting companion that sometimes Trifid Nebula contains Cepheid variable stars eclipses it. Many, possibly most, stars have at least some variation in luminosity: the energy output of our Sun, for example, varies by about 0.1% over an 11-year solar cycle.[1] Contents Discovery Detecting variability Variable star observations Interpretation of observations Nomenclature Classification Intrinsic variable stars Pulsating variable stars Eruptive variable stars Cataclysmic or explosive variable stars Extrinsic variable stars Rotating variable stars Eclipsing binaries Planetary transits See also References External links Discovery An ancient Egyptian calendar of lucky and unlucky days composed some 3,200 years ago may be the oldest preserved historical document of the discovery of a variable star, the eclipsing binary Algol.[2][3][4] Of the modern astronomers, the first variable star was identified in 1638 when Johannes Holwarda noticed that Omicron Ceti (later named Mira) pulsated in a cycle taking 11 months; the star had previously been described as a nova by David Fabricius in 1596. This discovery, combined with supernovae observed in 1572 and 1604, proved that the starry sky was not eternally invariable as Aristotle and other ancient philosophers had taught. -
Astronomy General Information
ASTRONOMY GENERAL INFORMATION HERTZSPRUNG-RUSSELL (H-R) DIAGRAMS -A scatter graph of stars showing the relationship between the stars’ absolute magnitude or luminosities versus their spectral types or classifications and effective temperatures. -Can be used to measure distance to a star cluster by comparing apparent magnitude of stars with abs. magnitudes of stars with known distances (AKA model stars). Observed group plotted and then overlapped via shift in vertical direction. Difference in magnitude bridge equals distance modulus. Known as Spectroscopic Parallax. SPECTRA HARVARD SPECTRAL CLASSIFICATION (1-D) -Groups stars by surface atmospheric temp. Used in H-R diag. vs. Luminosity/Abs. Mag. Class* Color Descr. Actual Color Mass (M☉) Radius(R☉) Lumin.(L☉) O Blue Blue B Blue-white Deep B-W 2.1-16 1.8-6.6 25-30,000 A White Blue-white 1.4-2.1 1.4-1.8 5-25 F Yellow-white White 1.04-1.4 1.15-1.4 1.5-5 G Yellow Yellowish-W 0.8-1.04 0.96-1.15 0.6-1.5 K Orange Pale Y-O 0.45-0.8 0.7-0.96 0.08-0.6 M Red Lt. Orange-Red 0.08-0.45 *Very weak stars of classes L, T, and Y are not included. -Classes are further divided by Arabic numerals (0-9), and then even further by half subtypes. The lower the number, the hotter (e.g. A0 is hotter than an A7 star) YERKES/MK SPECTRAL CLASSIFICATION (2-D!) -Groups stars based on both temperature and luminosity based on spectral lines. -
Gamma-Ray Burst Progenitors
Space Sci Rev (2016) 202:33–78 DOI 10.1007/s11214-016-0312-x Gamma-Ray Burst Progenitors Andrew Levan1 · Paul Crowther2 · Richard de Grijs3,4 · Norbert Langer5 · Dong Xu6,7,8 · Sung-Chul Yoon9 Received: 26 August 2016 / Accepted: 8 November 2016 / Published online: 21 November 2016 © The Author(s) 2016. This article is published with open access at Springerlink.com Abstract We review our current understanding of the progenitors of both long and short duration gamma-ray bursts (GRBs). Constraints can be derived from multiple directions, and we use three distinct strands; (i) direct observations of GRBs and their host galaxies, (ii) parameters derived from modelling, both via population synthesis and direct numerical simulation and (iii) our understanding of plausible analog progenitor systems observed in the local Universe. From these joint constraints, we describe the likely routes that can drive B A. Levan [email protected] P. Crowther Paul.crowther@sheffield.ac.uk R. de Grijs [email protected] N. Langer [email protected] D. Xu [email protected] S.-C. Yoon [email protected] 1 Department of Physics, University of Warwick, Coventry, CV4 7AL, UK 2 Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK 3 Kavli Institute for Astronomy & Astrophysics and Department of Astronomy, Peking University, Yi He Yuan Lu 5, Hai Dian District, Beijing 100871, China 4 International Space Science Institute–Beijing, 1 Nanertiao, Zhongguancun, Hai Dian District, Beijing 100190, China 5 Argelander-Institut für Astronomie der Universität Bonn, Auf dem Hügel 71, 53121, Bonn, Germany 6 Dark Cosmology Centre, Niels-Bohr-Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark 7 National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China 34 A.