Fred Hoyle and the 7.65 Mev Carbon Resonance
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Collapsars As a Major Source of R-Process Elements
Collapsars as a major source of r-process elements Daniel M. Siegel1;2;3;4;5, Jennifer Barnes1;2;5 & Brian D. Metzger1;2 1Department of Physics, Columbia University, New York, NY, USA 2Columbia Astrophysics Laboratory, Columbia University, New York, NY, USA 3Perimeter Institute for Theoretical Physics, Waterloo, Ontario, Canada 4Department of Physics, University of Guelph, Guelph, Ontario, Canada 5NASA Einstein Fellow The production of elements by rapid neutron capture (r-process) in neutron-star mergers is expected theoretically and is supported by multimessenger observations1–3 of gravitational- wave event GW170817: this production route is in principle sufficient to account for most of the r-process elements in the Universe4. Analysis of the kilonova that accompanied GW170817 identified5, 6 delayed outflows from a remnant accretion disk formed around the newly born black hole7–10 as the dominant source of heavy r-process material from that event9, 11. Sim- ilar accretion disks are expected to form in collapsars (the supernova-triggering collapse of rapidly rotating massive stars), which have previously been speculated to produce r-process elements12, 13. Recent observations of stars rich in such elements in the dwarf galaxy Retic- arXiv:1810.00098v2 [astro-ph.HE] 14 Aug 2020 ulum II14, as well as the Galactic chemical enrichment of europium relative to iron over longer timescales15, 16, are more consistent with rare supernovae acting at low stellar metal- licities than with neutron-star mergers. Here we report simulations that show that collapsar accretion disks yield sufficient r-process elements to explain observed abundances in the Uni- 1 verse. Although these supernovae are rarer than neutron- star mergers, the larger amount of material ejected per event compensates for the lower rate of occurrence. -
Anthropic Measure of Hominid (And Other) Terrestrials. Brandon Carter Luth, Observatoire De Paris-Meudon
Anthropic measure of hominid (and other) terrestrials. Brandon Carter LuTh, Observatoire de Paris-Meudon. Provisional draft, April 2011. Abstract. According to the (weak) anthropic principle, the a priori proba- bility per unit time of finding oneself to be a member of a particular popu- lation is proportional to the number of individuals in that population, mul- tiplied by an anthropic quotient that is normalised to unity in the ordinary (average adult) human case. This quotient might exceed unity for conceiv- able superhuman extraterrestrials, but it should presumably be smaller for our terrestrial anthropoid relations, such as chimpanzees now and our pre- Neanderthal ancestors in the past. The (ethically relevant) question of how much smaller can be addressed by invoking the anthropic finitude argument, using Bayesian reasonning, whereby it is implausible a posteriori that the total anthropic measure should greatly exceed the measure of the privileged subset to which we happen to belong, as members of a global civilisation that has (recently) entered a climactic phase with a timescale of demographic expansion and technical development short compared with a breeding gen- eration. As well as “economist’s dream” scenarios with continual growth, this finitude argument also excludes “ecologist’s dream” scenarios with long term stabilisation at some permanently sustainable level, but it it does not imply the inevitability of a sudden “doomsday” cut-off. A less catastrophic likelihood is for the population to decline gradually, after passing smoothly through a peak value that is accounted for here as roughly the information content ≈ 1010 of our genome. The finitude requirement limits not just the future but also the past, of which the most recent phase – characterised by memetic rather than genetic evolution – obeyed the Foerster law of hyperbolic population growth. -
Cometary Panspermia a Radical Theory of Life’S Cosmic Origin and Evolution …And Over 450 Articles, ~ 60 in Nature
35 books: Cosmic origins of life 1976-2020 Physical Sciences︱ Chandra Wickramasinghe Cometary panspermia A radical theory of life’s cosmic origin and evolution …And over 450 articles, ~ 60 in Nature he combined efforts of generations supporting panspermia continues to Prof Wickramasinghe argues that the seeds of all life (bacteria and viruses) Panspermia has been around may have arrived on Earth from space, and may indeed still be raining down some 100 years since the term of experts in multiple fields, accumulate (Wickramasinghe et al., 2018, to affect life on Earth today, a concept known as cometary panspermia. ‘primordial soup’, referring to Tincluding evolutionary biology, 2019; Steele et al., 2018). the primitive ocean of organic paleontology and geology, have painted material not-yet-assembled a fairly good, if far-from-complete, picture COMETARY PANSPERMIA – cultural conceptions of life dating back galactic wanderers are normal features have argued that these could not into living organisms, was first of how the first life on Earth progressed A SOLUTION? to the ideas of Aristotle, and that this of the cosmos. Comets are known to have been lofted from the Earth to a coined. The question of how from simple organisms to what we can The word ‘panspermia’ comes from the may be the source of some of the have significant water content as well height of 400km by any known process. life’s molecular building blocks see today. However, there is a crucial ancient Greek roots ‘sperma’ meaning more hostile resistance the idea of as organics, and their cores, kept warm Bacteria have also been found high in spontaneously assembled gap in mainstream understanding - seed, and ‘pan’, meaning all. -
Fred Hoyle: Pioneer in Nuclear Astrophysics
PERSONALITY Fred Hoyle: pioneer in nuclear astrophysics Fred Hoyle, who died in 2001, is best known as a cosmologist. But, as Simon Mitton relates, his career in physics began with the weak interaction and moved on to a crucial discovery in nuclear physics. Fred Hoyle, the great cosmologist, nuclear astrophysicist and contro versialist, was born 90 years ago in the beautiful county of Yorkshire in the north of England. Hoyle's first science teacher was his father, who supplied the boy with books and apparatus for chemistry exper iments. By the age of 15 he was making highly toxic phosphine (PH3) Later in life Hoyle seldom worked at a desk in a faculty building, in his mother's kitchen, and terrifying his young sister with explosions. preferring a comfortable armchair at home. (St John's College.) In high school he excelled in mathematics, chemistry and physics, and in 1933 won a place at Cambridge to study physics. time Hoyle tracked him down he had just returned from spending six On arrival at Cambridge he immediately demonstrated his fierce months in Rome with Enrico Fermi. Peierls immediately set Hoyle independence by telling his astonished tutor that he was switching the task of improving Fermi's theory of beta decay, published in from physics to applied mathematics. The future nuclear astro 1934. This led, in 1937, to Hoyle's first research paper, "The gen physicist foresaw that Cambridge mathematics rather than lab eralised Fermi interaction". oratory physics would give him the right start as a theorist. The In 1938 Paul Dirac, who had won the Nobel prize in 1933, country boy displayed an astonishing talent at mathematics, even became Hoyle's supervisor because Peierls had left Cambridge for by the highest standards of the university. -
Editorial Note To: Brandon Carter, Large Number Coincidences and the Anthropic Principle in Cosmology
Gen Relativ Gravit (2011) 43:3213–3223 DOI 10.1007/s10714-011-1257-8 GOLDEN OLDIE EDITORIAL Editorial note to: Brandon Carter, Large number coincidences and the anthropic principle in cosmology George F. R. Ellis Published online: 27 September 2011 © Springer Science+Business Media, LLC 2011 Keywords Cosmology · Confrontation of cosmological theories with observational data · Anthropic principle · World ensemble · Golden Oldie Editorial The anthropic principle is one of the most controversial proposals in cosmology. It relates to why the universe is of such a nature as to allow the existence of life. This inevitably engages with the foundations of cosmology, and has philosophical as well as technical aspects. The literature on the topic is vast—the Carter paper reprinted here [10] has 226 listed citations, and the Barrow and Tipler book [3] has 1,740. Obviously I can only pick up on a few of these papers in this brief review of the impact of the paper. While there were numerous previous philosophical treatises on the topic, stretching back to speculations about the origin of the universe in ancient times (see [3]fora magisterial survey), scientific studies are more recent. A well known early one was by biologist Alfred Russell Wallace, who wrote in 1904: “Such a vast and complex uni- verse as that which we know exists around us, may have been absolutely required … in order to produce a world that should be precisely adapted in every detail for the orderly development of life culminating in man” [50]. But that was before modern cosmology was established: the idea of the expanding and evolving universe was yet to come. -
Minicourses in Astrophysics, Modular Approach, Vol
DOCUMENT RESUME ED 161 706 SE n325 160 ° TITLE Minicourses in Astrophysics, Modular Approach, Vol.. II. INSTITUTION Illinois Univ., Chicago. SPONS AGENCY National Science Foundation, Washington, D. BUREAU NO SED-75-21297 PUB DATE 77 NOTE 134.,; For related document,. see SE 025 159; Contains occasional blurred,-dark print EDRS PRICE MF-$0.83 HC- $7..35 Plus Postage. DESCRIPTORS *Astronomy; *Curriculum Guides; Evolution; Graduate 1:-Uldy; *Higher Edhcation; *InstructionalMaterials; Light; Mathematics; Nuclear Physics; *Physics; Radiation; Relativity: Science Education;. *Short Courses; Space SCiences IDENTIFIERS *Astrophysics , , ABSTRACT . This is the seccA of a two-volume minicourse in astrophysics. It contains chaptez:il on the followingtopics: stellar nuclear energy sources and nucleosynthesis; stellarevolution; stellar structure and its determinatioli;.and pulsars.Each chapter gives much technical discussion, mathematical, treatment;diagrams, and examples. References are-included with each chapter.,(BB) e. **************************************t****************************- Reproductions supplied by EDRS arethe best-that can be made * * . from the original document. _ * .**************************4******************************************** A U S DEPARTMENT OF HEALTH. EDUCATION &WELFARE NATIONAL INSTITUTE OF EDUCATION THIS DOCUMENT AS BEEN REPRO' C'')r.EC! EXACTLY AS RECEIVED FROM THE PERSON OR ORGANIZATION'ORIGIkl A TINC.IT POINTS OF VIEW OR OPINIONS aft STATED DO NOT NECESSARILY REPRE SENT OFFICIAL NATIONAL INSTITUTE Of EDUCATION POSITION OR POLICY s. MINICOURSES IN ASTROPHYSICS MODULAR APPROACH , VOL. II- FA DEVELOPED'AT THE hlIVERSITY OF ILLINOIS AT CHICAGO 1977 I SUPPORTED BY NATIONAL SCIENCE FOUNDATION DIRECTOR: S. SUNDARAM 'ASSOCIATETIRECTOR1 J. BURNS _DEPARTMENT OF PHYSICS. DEPARTMENT OF PHYSICS AND SPACE UNIVERSITY OF ILLINOIS SCIENCES CHICAGO, ILLINOIS 60680 FLORIDA INSTITUTE OF TECHNOLOGY MELBOURNE, FLORIDA 32901 0 0 4, STELLAR NUCLEAR ENERGY SOURCES and NUCLEGSYNTHESIS 'I. -
Fred Hoyle's Universe
GENERAL ARTICLE Fred Hoyle’s Universe Jayant V Narlikar This article recalls some of the seminal contri- butions to astronomy made by Fred Hoyle. His ideas were thought to be unrealistic at the time they were proposed, but have now been assim- ilated into mainstream science. A general com- ment that emerges from such examples is that highly creative individuals who are far ahead of their times do not get the recognition they de- Jayant V Narlikar is a serve once their ideas are rediscovered and ac- cosmologist and theoretical cepted as standard: for, by the time this hap- astrophysicist. He was a pens, they and their contributions are forgotten. research student and a long-time collaborator of 1. Introduction Fred Hoyle. He is the Founder Director of Fred Hoyle was arguably the most imaginative astro- IUCCA and is currently an emeritus professor there. physicist of the 20th century. He contributed very orig- He has made strong efforts inal ideas to astronomy and astrophysics in topics rang- to promote teaching and ing from the solar system to cosmology. He also made research in astronomy in contributions to fundamental physics, in particular to the universities. He has the concept of action at a distance. His studies on exo- written extensively in English and Marathi to biology evoked the most opposition from the Establish- popularize science. ment because their implications were so far reaching. This article presents glimpses of the work of this mul- tifaceted personality who is also known to the common man as an accomplished science populariser and writer of science ¯ction. -
Science Fiction Stories with Good Astronomy & Physics
Science Fiction Stories with Good Astronomy & Physics: A Topical Index Compiled by Andrew Fraknoi (U. of San Francisco, Fromm Institute) Version 7 (2019) © copyright 2019 by Andrew Fraknoi. All rights reserved. Permission to use for any non-profit educational purpose, such as distribution in a classroom, is hereby granted. For any other use, please contact the author. (e-mail: fraknoi {at} fhda {dot} edu) This is a selective list of some short stories and novels that use reasonably accurate science and can be used for teaching or reinforcing astronomy or physics concepts. The titles of short stories are given in quotation marks; only short stories that have been published in book form or are available free on the Web are included. While one book source is given for each short story, note that some of the stories can be found in other collections as well. (See the Internet Speculative Fiction Database, cited at the end, for an easy way to find all the places a particular story has been published.) The author welcomes suggestions for additions to this list, especially if your favorite story with good science is left out. Gregory Benford Octavia Butler Geoff Landis J. Craig Wheeler TOPICS COVERED: Anti-matter Light & Radiation Solar System Archaeoastronomy Mars Space Flight Asteroids Mercury Space Travel Astronomers Meteorites Star Clusters Black Holes Moon Stars Comets Neptune Sun Cosmology Neutrinos Supernovae Dark Matter Neutron Stars Telescopes Exoplanets Physics, Particle Thermodynamics Galaxies Pluto Time Galaxy, The Quantum Mechanics Uranus Gravitational Lenses Quasars Venus Impacts Relativity, Special Interstellar Matter Saturn (and its Moons) Story Collections Jupiter (and its Moons) Science (in general) Life Elsewhere SETI Useful Websites 1 Anti-matter Davies, Paul Fireball. -
Announcements
Announcements • Next Session – Stellar evolution • Low-mass stars • Binaries • High-mass stars – Supernovae – Synthesis of the elements • Note: Thursday Nov 11 is a campus holiday Red Giant 8 100Ro 10 years L 10 3Ro, 10 years Temperature Red Giant Hydrogen fusion shell Contracting helium core Electron Degeneracy • Pauli Exclusion Principle says that you can only have two electrons per unit 6-D phase- space volume in a gas. DxDyDzDpxDpyDpz † Red Giants • RG Helium core is support against gravity by electron degeneracy • Electron-degenerate gases do not expand with increasing temperature (no thermostat) • As the Temperature gets to 100 x 106K the “triple-alpha” process (Helium fusion to Carbon) can happen. Helium fusion/flash Helium fusion requires two steps: He4 + He4 -> Be8 Be8 + He4 -> C12 The Berylium falls apart in 10-6 seconds so you need not only high enough T to overcome the electric forces, you also need very high density. Helium Flash • The Temp and Density get high enough for the triple-alpha reaction as a star approaches the tip of the RGB. • Because the core is supported by electron degeneracy (with no temperature dependence) when the triple-alpha starts, there is no corresponding expansion of the core. So the temperature skyrockets and the fusion rate grows tremendously in the `helium flash’. Helium Flash • The big increase in the core temperature adds momentum phase space and within a couple of hours of the onset of the helium flash, the electrons gas is no longer degenerate and the core settles down into `normal’ helium fusion. • There is little outward sign of the helium flash, but the rearrangment of the core stops the trip up the RGB and the star settles onto the horizontal branch. -
Low-Energy Nuclear Physics Part 2: Low-Energy Nuclear Physics
BNL-113453-2017-JA White paper on nuclear astrophysics and low-energy nuclear physics Part 2: Low-energy nuclear physics Mark A. Riley, Charlotte Elster, Joe Carlson, Michael P. Carpenter, Richard Casten, Paul Fallon, Alexandra Gade, Carl Gross, Gaute Hagen, Anna C. Hayes, Douglas W. Higinbotham, Calvin R. Howell, Charles J. Horowitz, Kate L. Jones, Filip G. Kondev, Suzanne Lapi, Augusto Macchiavelli, Elizabeth A. McCutchen, Joe Natowitz, Witold Nazarewicz, Thomas Papenbrock, Sanjay Reddy, Martin J. Savage, Guy Savard, Bradley M. Sherrill, Lee G. Sobotka, Mark A. Stoyer, M. Betty Tsang, Kai Vetter, Ingo Wiedenhoever, Alan H. Wuosmaa, Sherry Yennello Submitted to Progress in Particle and Nuclear Physics January 13, 2017 National Nuclear Data Center Brookhaven National Laboratory U.S. Department of Energy USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26) Notice: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No.DE-SC0012704 with the U.S. Department of Energy. The publisher by accepting the manuscript for publication acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or any third party’s use or the results of such use of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. -
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. -
Alpha Process
Alpha process The alpha process, also known as the alpha ladder, is one of two classes of nuclear fusion reactions by which stars convert helium into heavier elements, the other being the triple-alpha process.[1] The triple-alpha process consumes only helium, and produces carbon. After enough carbon has accumulated, the reactions below take place, all consuming only helium and the product of the previous reaction. E is the energy produced by the reaction, released primarily as gamma rays (γ). It is a common misconception that the above sequence ends at (or , which is a decay product of [2]) because it is the most stable nuclide - i.e., it has the highest nuclear binding energy per nucleon, and production of heavier nuclei requires energy (is endothermic) instead of releasing it (exothermic). (Nickel-62) is actually the most stable nuclide.[3] However, the sequence ends at because conditions in the stellar interior cause the competition between photodisintegration and the alpha process to favor photodisintegration around iron,[2][4] leading to more being produced than . All these reactions have a very low rate at the temperatures and densities in stars and therefore do not contribute significantly to a star's energy production; with elements heavier than neon (atomic number > 10), they occur even less easily due to the increasing Coulomb barrier. Alpha process elements (or alpha elements) are so-called since their most abundant isotopes are integer multiples of four, the mass of the helium nucleus (the alpha particle); these isotopes are known as alpha nuclides. Stable alpha elements are: C, O, Ne, Mg, Si, and S; Ar and Ca are observationally stable.