DOCSLIB.ORG

Neutron Stars & Black Holes

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Neutron Stars & Black Holes Introduction ? Recall that White Dwarfs are the second most common type of star. ? They are the remains of medium-sized stars - hydrogen fused to helium Neutron Stars - failed to ignite carbon - drove away their envelopes to from planetary nebulae & - collapsed and cooled to form White Dwarfs ? The more massive a White Dwarf, the smaller its radius Black Holes ? Stars more massive than the Chandrasekhar limit of 1.4 solar masses cannot be White Dwarfs Formation of Neutron Stars As the core of a massive star (residual mass greater than 1.4 ?Supernova 1987A solar masses) begins to collapse: (arrow) in the Large - density quickly reaches that of a white dwarf Magellanic Cloud was - but weight is too great to be supported by degenerate the first supernova electrons visible to the naked eye - collapse of core continues; atomic nuclei are broken apart since 1604. by gamma rays - Almost instantaneously, the increasing density forces freed electrons to absorb electrons to form neutrons - the star blasts away in a supernova explosion leaving behind a neutron star. Properties of Neutron Stars Crab Nebula ? Neutrons stars predicted to have a radius of about 10 km ? In CE 1054, Chinese and a density of 1014 g/cm3 . astronomers saw a ? This density is about the same as the nucleus supernova ? A sugar-cube-sized lump of this material would weigh 100 ? Pulsar is at center (arrow) million tons ? It is very energetic; pulses ? The mass of a neutron star cannot be more than 2-3 solar are detectable at visual masses wavelengths ? Neutron stars are predicted to rotate very fast, to be very ? Inset image taken by hot, and have a strong magnetic field. Hubble Space Telescope ? Such objects have been identified as pulsars, sources of pulsed radio energy. 1 Pulsars ? Pulsars are spinning ? A few pulsars have been neutron stars found in binary systems ? They emit beams of ? Astronomers can estimate radiation from their the masses of the pulsars magnetic poles ? In some binary systems, ? As they spin, the beams such as Hercules X-1,mass sweep through the sky like flows into a hot, accretion a lighthouse diskaround the neutron star ? X rays are emitted Black Holes ?If the core of a star collapses and contains more ? Escape Velocity is the than 3 solar masses, no force can stop it. initial velocity an object needs to escape from a ?As object shrinks, its density and gravitational celestial body. strength increase. ? For Earth, escape velocity ?If it shrinks to zero radius, its density and gravity is 11 km/s (25 000 mph) become infinite. ?Such a point is called a Singularity ?A black hole is formed Entering a Black Hole ? A black hole forms when ? If we were to leap, feet an object collapses to a first, into a black hole, small size ( perhaps to a outside observers would singularity) notice two relativistic ? The escape velocity in its effects. neighborhood is so great ? Time dilation- they would light cannot escape see our clock slow down ? This boundary is the ? Our light would seem to be Event Horizon red-shifted to longer ? Radius R S is wavelengths Schwarzschildradius ? We would not notice these ? Events inside event effects horizon cannot be seen 2 Entering a Black Hole Entering a Black Hole ?Entering feet first ? As we fell closer, tidal toward event horizon, forces would crush our we would feel our feet bodies laterally, and being pulled more stretch it longitudinally, strongly than our long before reaching the heads. event horizon ?This is a tidal force ? Friction from distortion would heat up our ?It will at first be minor bodies to millions of degrees ? We would emit X rays & Gamma rays Search for Black Holes Search for black Holes ?Do black holes exist? ? Cygnus X-1 was first candidate ? Consists of supergiant O star ?A black hole alone is totally invisible. with strong stellar wind, ?If a gas is flowing rapidly into it, the gas will heat carrying gas into a hot accretion up and emit X-rays before it enters event disk around a compact object. horizon. ? Doppler shift suggests that mass of compact object is about 10-15 ?Consider a black hole in a close binary system. solar masses ?Black hole could drain mass from companion ? Good candidate, but not 100% star, and form a hot accretion disk that would conclusive ? A few dozen more candidates, emit X-rays such as LMC X-3, V616 Mon, QZ Vul, … Misconceptions of Black Holes ? Black holes exist only in theory. ? Black holes are giant cosmic vacuum cleaners that swallow Recent observations obtained by the Hubble Space up everything around them. Telescope have given considerable support to the presence In reality, at a given distance from its center a black hole of supermassive black holes at the centers of some galaxies, creates the same gravity as would a normal object with the but there is not yet absolute proof. There has been very same mass. Therefore, black holes at a distance do not attract good evidence for the existence of stellar black holes for at matter more strongly than ordinary stars do. However, another least 20 years, based on the effects of an unseen companion important factor that determines the magnitude of the force of in the double-star system, Cygnus X-1. The existence of gravity is the radius of the object. The mass of a black hole is black holes seems likely, given our understanding of so compressed that it is possible to get very close to its center physical processes, but it is not absolutely confirmed. where gravity will be enormously strong. 3 ?Black holes can be detected visually. ?Our Sun will become a black hole. We observe black holes indirectly by the effect Only stars that are more massive than our Sun they have on material around them, but by might become black holes when they run out of definition a black hole cannot be "seen." fuel at the end of their lives. The Sun is not massive enough to become a black hole. Model of a Black Hole 4.
Load more

Recommended publications
  • Exploring Pulsars
    High-energy astrophysics Explore the PUL SAR menagerie Astronomers are discovering many strange properties of compact stellar objects called pulsars. Here’s how they fit together. by Victoria M. Kaspi f you browse through an astronomy book published 25 years ago, you’d likely assume that astronomers understood extremely dense objects called neutron stars fairly well. The spectacular Crab Nebula’s central body has been a “poster child” for these objects for years. This specific neutron star is a pulsar that I rotates roughly 30 times per second, emitting regular appar- ent pulsations in Earth’s direction through a sort of “light- house” effect as the star rotates. While these textbook descriptions aren’t incorrect, research over roughly the past decade has shown that the picture they portray is fundamentally incomplete. Astrono- mers know that the simple scenario where neutron stars are all born “Crab-like” is not true. Experts in the field could not have imagined the variety of neutron stars they’ve recently observed. We’ve found that bizarre objects repre- sent a significant fraction of the neutron star population. With names like magnetars, anomalous X-ray pulsars, soft gamma repeaters, rotating radio transients, and compact Long the pulsar poster child, central objects, these bodies bear properties radically differ- the Crab Nebula’s central object is a fast-spinning neutron star ent from those of the Crab pulsar. Just how large a fraction that emits jets of radiation at its they represent is still hotly debated, but it’s at least 10 per- magnetic axis. Astronomers cent and maybe even the majority.
    [Show full text]
  • Neutron Stars
    Chandra X-Ray Observatory X-Ray Astronomy Field Guide Neutron Stars Ordinary matter, or the stuff we and everything around us is made of, consists largely of empty space. Even a rock is mostly empty space. This is because matter is made of atoms. An atom is a cloud of electrons orbiting around a nucleus composed of protons and neutrons. The nucleus contains more than 99.9 percent of the mass of an atom, yet it has a diameter of only 1/100,000 that of the electron cloud. The electrons themselves take up little space, but the pattern of their orbit defines the size of the atom, which is therefore 99.9999999999999% Chandra Image of Vela Pulsar open space! (NASA/PSU/G.Pavlov et al. What we perceive as painfully solid when we bump against a rock is really a hurly-burly of electrons moving through empty space so fast that we can't see—or feel—the emptiness. What would matter look like if it weren't empty, if we could crush the electron cloud down to the size of the nucleus? Suppose we could generate a force strong enough to crush all the emptiness out of a rock roughly the size of a football stadium. The rock would be squeezed down to the size of a grain of sand and would still weigh 4 million tons! Such extreme forces occur in nature when the central part of a massive star collapses to form a neutron star. The atoms are crushed completely, and the electrons are jammed inside the protons to form a star composed almost entirely of neutrons.
    [Show full text]
  • Astro 210 Lecture 37 April 23, 2018 Announcements
    Astro 210 Lecture 37 April 23, 2018 Announcements: • HW 11: The Final Frontier posted, due 5:00pm Friday • Grades: we are catching up! keep checking Moodle 1 Last Time: Searching for Black Holes Black holes themselves are invisible∗ can can detect them via their strong gravitational effects on their close surroundings example: binary stars X-rays emitted from unseen massive companion ∗this ignores Hawking radiation–see below 2 Our Own Galactic Center central ∼ 30 pc of Galaxy: can’t see optically (Q: why?), but can in other wavelengths: extended (non-point) radio emission (Sagittarius A) from high-energy electrons radio source at center: Sgr A∗ size 2.4 AU(!), variable emission in radio, X-ray www: X-ray Sgr A∗ in infrared wavelengths: can see stars near Sgr A∗ and they move! www: Sgr A∗ movie elliptical paths! closest: period P = 15.2 yr semi-major axis: a = 4.64 × 10−3 pc 3 6 → enclosed mass (3.7 ± 1.5) × 10 M⊙ Q: and so? the center of our Galaxy contains a black hole! Sgr A∗ Schwarzschild radius 7 −7 rSch = 1.1 × 10 km=0.74 AU = 3.6 × 10 pc (1) → not resolved (yet) but: Event Horizon Telescope has data and right now is processing possible first images! Galactic black hole raises many questions: • how did it get there? • Sgr A∗ low luminosity, “quiet” compared to more “active” galactic nuclei www: AGN: M87 why? open question.... • in last few months: discovery of high-energy “bubbles” 4 above & below Galactic center www: gamma-ray images → remains of the most recent Sgr A∗ belch? Galaxies and Black Holes The Milky Way is not the only
    [Show full text]
  • Arxiv:Gr-Qc/0612030 V1 5 Dec 2006
    December 6, 2006 1:49 WSPC - Proceedings Trim Size: 9.75in x 6.5in main 1 STABLE DARK ENERGY STARS: AN ALTERNATIVE TO BLACK HOLES? FRANCISCO S. N. LOBO Centro de Astronomia e Astrof´ısica da Universidade de Lisboa, Campo Grande, Ed. C8 1749-016 Lisboa, Portugal flobo@cosmo.fis.fc.ul.pt In this work, a generalization of the Mazur-Mottola gravastar model is explored, by considering a matching of an interior solution governed by the dark energy equation of state, ω ≡ p/ρ < −1/3, to an exterior Schwarzschild vacuum solution at a junction interface, situated near to where the event horizon is expected to form. The motivation for implementing this generalization arises from the fact that recent observations have confirmed an accelerated cosmic expansion, for which dark energy is a possible candidate. Keywords: Gravastars; dark energy. Although evidence for the existence of black holes is very convincing, a certain amount of scepticism regarding the physical reality of singularities and event hori- zons is still encountered. In part, due to this scepticism, an alternative picture for the final state of gravitational collapse has emerged, where an interior compact ob- ject is matched to an exterior Schwarzschild vacuum spacetime, at or near where the event horizon is expected to form. Therefore, these alternative models do not possess a singularity at the origin and have no event horizon, as its rigid surface is arXiv:gr-qc/0612030 v1 5 Dec 2006 located at a radius slightly greater than the Schwarzschild radius. In particular, the gravastar (gravitational vacuum star) picture, proposed by Mazur and Mottola,1 has an effective phase transition at/near where the event horizon is expected to form, and the interior is replaced by a de Sitter condensate.
    [Show full text]
  • Pdf/44/4/905/5386708/44-4-905.Pdf
    MI-TH-214 INT-PUB-21-004 Axions: From Magnetars and Neutron Star Mergers to Beam Dumps and BECs Jean-François Fortin∗ Département de Physique, de Génie Physique et d’Optique, Université Laval, Québec, QC G1V 0A6, Canada Huai-Ke Guoy and Kuver Sinhaz Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019, USA Steven P. Harrisx Institute for Nuclear Theory, University of Washington, Seattle, WA 98195, USA Doojin Kim{ Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A&M University, College Station, TX 77843, USA Chen Sun∗∗ School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 69978, Israel (Dated: February 26, 2021) We review topics in searches for axion-like-particles (ALPs), covering material that is complemen- tary to other recent reviews. The first half of our review covers ALPs in the extreme environments of neutron star cores, the magnetospheres of highly magnetized neutron stars (magnetars), and in neu- tron star mergers. The focus is on possible signals of ALPs in the photon spectrum of neutron stars and gravitational wave/electromagnetic signals from neutron star mergers. We then review recent developments in laboratory-produced ALP searches, focusing mainly on accelerator-based facilities including beam-dump type experiments and collider experiments. We provide a general-purpose discussion of the ALP search pipeline from production to detection, in steps, and our discussion is straightforwardly applicable to most beam-dump type and reactor experiments. We end with a selective look at the rapidly developing field of ultralight dark matter, specifically the formation of Bose-Einstein Condensates (BECs).
    [Show full text]
  • R-Process Elements from Magnetorotational Hypernovae
    r-Process elements from magnetorotational hypernovae D. Yong1,2*, C. Kobayashi3,2, G. S. Da Costa1,2, M. S. Bessell1, A. Chiti4, A. Frebel4, K. Lind5, A. D. Mackey1,2, T. Nordlander1,2, M. Asplund6, A. R. Casey7,2, A. F. Marino8, S. J. Murphy9,1 & B. P. Schmidt1 1Research School of Astronomy & Astrophysics, Australian National University, Canberra, ACT 2611, Australia 2ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia 3Centre for Astrophysics Research, Department of Physics, Astronomy and Mathematics, University of Hertfordshire, Hatfield, AL10 9AB, UK 4Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 5Department of Astronomy, Stockholm University, AlbaNova University Center, 106 91 Stockholm, Sweden 6Max Planck Institute for Astrophysics, Karl-Schwarzschild-Str. 1, D-85741 Garching, Germany 7School of Physics and Astronomy, Monash University, VIC 3800, Australia 8Istituto NaZionale di Astrofisica - Osservatorio Astronomico di Arcetri, Largo Enrico Fermi, 5, 50125, Firenze, Italy 9School of Science, The University of New South Wales, Canberra, ACT 2600, Australia Neutron-star mergers were recently confirmed as sites of rapid-neutron-capture (r-process) nucleosynthesis1–3. However, in Galactic chemical evolution models, neutron-star mergers alone cannot reproduce the observed element abundance patterns of extremely metal-poor stars, which indicates the existence of other sites of r-process nucleosynthesis4–6. These sites may be investigated by studying the element abundance patterns of chemically primitive stars in the halo of the Milky Way, because these objects retain the nucleosynthetic signatures of the earliest generation of stars7–13.
    [Show full text]
  • The Twenty−Eight Lunar Mansions of China
    浜松医科大学紀要 一般教育 第5号（1991） THE TWENTY－EIGHT LUNAR MANSIONS OF CHINA （中国の二十八宿） David B． Kelley （英 語〉 Abstract： This’Paper attempts to place the development of the Chinese system ・fTw・nty－Eight Luna・ Man・i・n・（；＋八宿）i・・血・lti－cult・・al f・am・w・・k， withi・ which， contributions from cultures outside of China may be recognized． lt・ system－ atically compares the Chinese system with similar systems from Babylonia， Arabia，・ and lndia． The results of such a comparison not only suggest an early date for its development， but also a significant level of input from， most likely， a Middle Eastern source． Significantly， the data suggest an awareness， on the part of the ancient Chinese， of completely arbitrary groupings of stars （the twelve constellations of the Middle Eastern Zodiac）， as well as their equally arbitrary syMbolic associ－ ations． The paper also attempts to elucidate the graphic and organizational relation－ ship between the Chinese system of lunar mansions and （1．） Phe twelve Earthly Branches（地支）and（2．）the ten Heavenly S．tems（天干）． key words二China， Lunar calender， Lunar mansions， Zodiac． O． INTRODUCTION The time it takes the Moon to circle the Earth is 29 days， 12 hours， and 44 minutes． However， the time it takes the moon to return to the same （fixed一） star position amounts to some 28 days． ln China， it is the latter period that was and is of greater significance． The Erh－Shih－Pα一Hsui（一Kung）， the Twenty－Eight－lnns（Mansions），二十八 宿（宮），is the usual term in（Mandarin）Chinese， and includes 28 names for each day of such a month． ln East Asia， what is not
    [Show full text]
  • Magnetars: Explosive Neutron Stars with Extreme Magnetic Fields
    Magnetars: explosive neutron stars with extreme magnetic fields Nanda Rea Institute of Space Sciences, CSIC-IEEC, Barcelona 1 How magnetars are discovered? Soft Gamma Repeaters Bright X-ray pulsars with 0.5-10keV spectra modelled by a thermal plus a non-thermal component Anomalous X-ray Pulsars Bright X-ray transients! Transients No more distinction between Anomalous X-ray Pulsars, Soft Gamma Repeaters, and transient magnetars: all showing all kind of magnetars-like activity. Nanda Rea CSIC-IEEC Magnetars general properties 33 36 Swift-XRT COMPTEL • X-ray pulsars Lx ~ 10 -10 erg/s INTEGRAL • strong soft and hard X-ray emission Fermi-LAT • short X/gamma-ray flares and long outbursts (Kuiper et al. 2004; Abdo et al. 2010) • pulsed fractions ranging from ~2-80 % • rotating with periods of ~0.3-12s • period derivatives of ~10-14-10-11 s/s • magnetic fields of ~1013-1015 Gauss (Israel et al. 2010) • glitches and timing noise (Camilo et al. 2006) • faint infrared/optical emission (K~20; sometimes pulsed and transient) • transient radio pulsed emission (see Woods & Thompson 2006, Mereghetti 2008, Rea & Esposito 2011 for a review) Nanda Rea CSIC-IEEC How magnetar persistent emission is believed to work? • Magnetars have magnetic fields twisted up, inside and outside the star. • The surface of a young magnetar is so hot that it glows brightly in X-rays. • Magnetar magnetospheres are filled by charged particles trapped in the twisted field lines, interacting with the surface thermal emission through resonant cyclotron scattering. (Thompson, Lyutikov & Kulkarni 2002; Fernandez & Thompson 2008; Nobili, Turolla & Zane 2008a,b; Rea et al.
    [Show full text]
  • Search for Long-Duration Transient Gravitational Waves Associated with Magnetar Bursts During Ligo’S Sixth Science Run
    SEARCH FOR LONG-DURATION TRANSIENT GRAVITATIONAL WAVES ASSOCIATED WITH MAGNETAR BURSTS DURING LIGO’S SIXTH SCIENCE RUN by RYAN QUITZOW-JAMES A DISSERTATION Presented to the Department of Physics and the Graduate School of the University of Oregon in partial fulfillment of the requirements for the degree of Doctor of Philosophy March 2016 DISSERTATION APPROVAL PAGE Student: Ryan Quitzow-James Title: Search for Long-Duration Transient Gravitational Waves Associated with Magnetar Bursts during LIGO’s Sixth Science Run This dissertation has been accepted and approved in partial fulfillment of the requirements for the Doctor of Philosophy degree in the Department of Physics by: James E. Brau Chair Raymond E. Frey Advisor Timothy Cohen Core Member Daniel A. Steck Core Member James A. Isenberg Institutional Representative and Scott L. Pratt Dean of the Graduate School Original approval signatures are on file with the University of Oregon Graduate School. Degree awarded March 2016 ii © 2016 Ryan Quitzow-James This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs (United States) License. iii DISSERTATION ABSTRACT Ryan Quitzow-James Doctor of Philosophy Department of Physics March 2016 Title: Search for Long-Duration Transient Gravitational Waves Associated with Magnetar Bursts during LIGO’s Sixth Science Run Soft gamma repeaters (SGRs) and anomalous X-ray pulsars are thought to be neutron stars with strong magnetic fields, called magnetars, which emit intermittent bursts of hard X-rays and soft gamma rays. Three highly energetic bursts, known as giant flares, have been observed originating from three different SGRs, the latest and most energetic of which occurred on December 27, 2004, from the SGR with the largest estimated magnetic field, SGR 1806-20.
    [Show full text]
  • Chapter 16 the Sun and Stars
    Chapter 16 The Sun and Stars Stargazing is an awe-inspiring way to enjoy the night sky, but humans can learn only so much about stars from our position on Earth. The Hubble Space Telescope is a school-bus-size telescope that orbits Earth every 97 minutes at an altitude of 353 miles and a speed of about 17,500 miles per hour. The Hubble Space Telescope (HST) transmits images and data from space to computers on Earth. In fact, HST sends enough data back to Earth each week to fill 3,600 feet of books on a shelf. Scientists store the data on special disks. In January 2006, HST captured images of the Orion Nebula, a huge area where stars are being formed. HST’s detailed images revealed over 3,000 stars that were never seen before. Information from the Hubble will help scientists understand more about how stars form. In this chapter, you will learn all about the star of our solar system, the sun, and about the characteristics of other stars. 1. Why do stars shine? 2. What kinds of stars are there? 3. How are stars formed, and do any other stars have planets? 16.1 The Sun and the Stars What are stars? Where did they come from? How long do they last? During most of the star - an enormous hot ball of gas day, we see only one star, the sun, which is 150 million kilometers away. On a clear held together by gravity which night, about 6,000 stars can be seen without a telescope.
    [Show full text]
  • CHIME and Probing the Origin of Fast Radio Bursts by Liam Dean Connor a Thesis Submitted in Conformity with the Requirements
    CHIME and Probing the Origin of Fast Radio Bursts by Liam Dean Connor A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Graduate Department of Astronomy and Astrophysics University of Toronto c Copyright 2016 by Liam Dean Connor Abstract CHIME and Probing the Origin of Fast Radio Bursts Liam Dean Connor Doctor of Philosophy Graduate Department of Astronomy and Astrophysics University of Toronto 2016 The time-variable long-wavelength sky harbours a number of known but unsolved astro- physical problems, and surely many more undiscovered phenomena. With modern tools such problems will become tractable, and new classes of astronomical objects will be revealed. These tools include digital telescopes made from powerful computing clusters, and improved theoretical methods. In this thesis we employ such devices to understand better several puzzles in the time-domain radio sky. Our primary focus is on the origin of fast radio bursts (FRBs), a new class of transients of which there seem to be thousands per sky per day. We offer a model in which FRBs are extragalactic but non-cosmological pulsars in young supernova remnants. Since this theoretical work was done, observations have corroborated the picture of FRBs as young rotating neutron stars, including the non-Poissonian repetition of FRB 121102. We also present statistical arguments regard- ing the nature and location of FRBs. These include reinstituting the classic V=Vmax-test @ log N to measure the brightness distribution of FRBs, i.e., constraining @ log S . We find consis- tency with a Euclidean distribution. This means current observations cannot distinguish between a cosmological population and a more local uniform population, unless added assumptions are made.
    [Show full text]
  • Binary Star Modeling: a Computational Approach
    TCNJ JOURNAL OF STUDENT SCHOLARSHIP VOLUME XIV APRIL 2012 BINARY STAR MODELING: A COMPUTATIONAL APPROACH Author: Daniel Silano Faculty Sponsor: R. J. Pfeiffer, Department of Physics ABSTRACT This paper illustrates the equations and computational logic involved in writing BinaryFactory, a program I developed in Spring 2011 in collaboration with Dr. R. J. Pfeiffer, professor of physics at The College of New Jersey. This paper outlines computational methods required to design a computer model which can show an animation and generate an accurate light curve of an eclipsing binary star system. The final result is a light curve fit to any star system using BinaryFactory. An example is given for the eclipsing binary star system TU Muscae. Good agreement with observational data was obtained using parameters obtained from literature published by others. INTRODUCTION This project started as a proposal for a simple animation of two stars orbiting one another in C++. I found that although there was software that generated simple animations of binary star orbits and generated light curves, the commercial software was prohibitively expensive or not very user friendly. As I progressed from solving the orbits to generating the Roche surface to generating a light curve, I learned much about computational physics. There were many trials along the way; this paper aims to explain to the reader how a computational model of binary stars is made, as well as how to avoid pitfalls I encountered while writing BinaryFactory. Binary Factory was written in C++ using the free C++ libraries, OpenGL, GLUT, and GLUI. A basis for writing a model similar to BinaryFactory in any language will be presented, with a light curve fit for the eclipsing binary star system TU Muscae in the final secion.
    [Show full text]