DOCSLIB.ORG

Black Holes, out of the Shadows 12.3.20 Amelia Chapman

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Black Holes, out of the Shadows 12.3.20 Amelia Chapman NASA’s Universe Of Learning: Black Holes, Out of the Shadows 12.3.20 Amelia Chapman: Welcome, everybody. This is Amelia and thanks for joining us today for Museum Alliance and Solar System Ambassador professional development conversation on NASA's Universe of Learning, on Black Holes: Out of the Shadows. I'm going to turn it over to Chris Britt to introduce himself and our speakers, and we'll get into it. Chris? Chris Britt: Thanks. Hello, this is Chris Britt from the Space Telescope Science Institute, with NASA's Universe of Learning. Welcome to today's science briefing. Thank you to everyone for joining us and for anyone listening to the recordings of this in the future. For this December science briefing, we're talking about something that always generates lots of questions from the public: Black holes. Probably one of the number one subjects that astronomers get asked about interacting with the public, and I do, too, when talking about astronomy. Questions like how do we know they're real? And what impact do they have on us? Or the universe is large? Slides for today's presentation can be found at the Museum Alliance and NASA Nationwide sites as well as NASA's Universe of Learning site. All of the recordings from previous talks should be up on those websites as well, which you are more than welcome to peruse at your leisure. As always, if you have any issues or questions, now or in the future, you can email Amelia Chapman at [email protected] or Museum Alliance members can contact her through the team chat app. Their info for that is on the Museum Alliance website. As a final reminder, for anyone who's calling in on phone lines, please do not put us on hold even if you have to step away because some phones will play holding music which can disrupt the talk. We have a panel of impressive speakers today. So I'll introduce them briefly as they come up to talk. But you can and should read their bios in full on their website as well. Please hold all your questions until all of the speakers have had a chance to present, and then we'll have a panel Q&A about black holes afterwards. Our first speaker for this briefing is Professor Tuan Do, who is the Deputy Director of the Galactic Center Group at UCLA. He received his PhD in astronomy from UCLA in 2010. He was a TMT Fellow at UC Irvine and a Dunlop Fellow at the University of Toronto. He's currently an assistant professor at UCLA, UCLA's Galactic Center Group, of course, was part of the Nobel Prize that was awarded this year for proving the existence of the black hole in center of our own galaxy, the Milky Way. So welcome, Dr. Do, and please take it away. Dr. Tuan Do: Great, thanks. Thanks, everyone for coming to this talk. I'm Tuan Do and I'm from UCLA. Today, I'd like to talk about how we can use the discovery of the supermassive black hole at the center of our galaxy as an example of how science works. I found that a lot of people are really fascinated by supermassive black holes from all ages and backgrounds. So it's a great topic to engage in discussions about how we know what we know about astronomy. We can't touch black holes, and we probably don't want to, but we can still learn amazing things about them. Next slide. This year, the Nobel Prize for Physics was awarded to three scientists: Roger Penrose, Reinhardt Genzel and Andrea Ghez. Roger Penrose won for his theoretical contributions to black holes, while Reinhard Genzel and Andrea Ghez won for showing that there was a supermassive black hole at the center of our Milky Way galaxy. So today, I'd like to talk about how this black hole was detected, how we were able to measure its mass, and what the future brings in this work. I'm concentrating the story from the perspective of Professor Ghez's work, since that's what I'm most familiar with. But the general framework will also apply to Reinhard Genzel's work as well. Next slide, please. One of the central aspects of the scientific process is hypothesis testing, and a lot of the discussion about this centers around the idea of proposing a hypothesis and then doing observations or experiments to see if it's consistent with the hypothesis. What I'm interested in is that it's a little bit more complicated than that. We're really never satisfied because one class we're continuously posing new questions in a really interesting feedback loop. So the story I want to tell today is about that feedback loop of hypothesis and observations. Next slide. So here's a picture of Professor Andrea Ghez very early in the morning after she got the call from the Nobel Committee about winning the prize. But let's start at the beginning of how this work began. So in the early '90s, there was starting to be evidence that the centers of galaxies can harbor supermassive black holes. These black holes have masses that are equivalent to millions of times that of our Sun, but they're pretty exciting objects. And there wasn't a lot known about them. But one of the best places to test for the existence of a supermassive black hole is in our very own backyard, at the center of our Milky Way galaxy. It has the highest concentration of stars anywhere in the galaxy. And there were suggestions and observations of radio wavelengths that there was maybe a massive object at the very center. So the initial hypothesis that Professor Ghez started with was that if there's a supermassive black hole at the center of our galaxy, its strong gravity should make the stars move really quickly around it. But there were a number of challenges, including Can you see enough stars? Can you see them move quickly enough to make these measurements. Next slide, please. This hypothesis requires a large telescope. And luckily, at the time, the largest optical and near infrared telescope at the time was just built in Hawaii. So this picture shows the two Keck telescopes. The mirror is about 10 meters. Next slide. And in the next slide, we see a picture of Professor Ghez next to the telescope in the background. She's standing in front of an astronomical instrument here. In this case, you can think of these instruments as giant digital cameras that can see infrared light. Next slide. This picture is now from the mid '90s, in a control room of a telescope. So this is kind of how astronomers do their work, Professor Ghez is in the blue sweater in the middle, this is still a pretty accurate view what we do at night. But computers are much fancier. But when we take the data and interact with the telescope in this way. Next slide, please. Using these first images, what do we see? In the top left is an actual image in the early '90s, of the center of the galaxy. The image has been inverted, so actually, the dark spots are the bright stars. And zoomed in, you can see a zoomed in portion of the middle with the stars are. And on the right is a plot showing the locations of these stars in 1995, 1996, and 1997. So really remarkably, the stars move, they're in different places each year. So it does indeed look like it starts moving quickly. So this is exactly what he predicted. There was a supermassive black hole. Next slide. Is our hypothesis test done? Well, we passed one test, but we'd like to be constrained to the black hole better. If there's a supermassive black hole, it should be very compact in size with a lot of mass in it. So that means a star should actually orbit it like the planets orbit our Sun. So we revise our hypothesis. If there's a supermassive black hole, that there should be a large amount of mass in a very small volume. Next slide. We need better technology to do this. Next slide. The first with of the development of adaptive optics on very large telescopes. Adaptive optics is this technology that lets us correct for the blurring effect on the atmosphere. This is why stars twinkle, for example. But it makes images blurry for telescopes on the ground. In this picture of two telescopes, two telescopes have lasers pointing at the center of a galaxy. This is an actual picture taken next to the telescope. Lasers kind of look like a Death Star from Star Wars, but really, all it does is it creates a spot of light at 90 kilometers up in the atmosphere. This creates an artificial star. So by observing how this artificial star changes a thousand times a second, we can measure the effect of the atmosphere and correct for it using sophisticated mirrors that can change shape to match the variations in the atmosphere. So this creates really sharp images as if the atmosphere wasn't there. Here's a picture of the center of the galaxy with adaptive optics. Oh, sorry, next slide. This whole image covers just a very tiny portion of the sky. So if you hold a strand of hair at arm's length, it would cover more of the sky than this picture.
Load more

Recommended publications
  • New APS CEO: Jonathan Bagger APS Sends Letter to Biden Transition
    Penrose’s Connecting students A year of Back Page: 02│ black hole proof 03│ and industry 04│ successful advocacy 08│ Bias in letters of recommendation January 2021 • Vol. 30, No. 1 aps.org/apsnews A PUBLICATION OF THE AMERICAN PHYSICAL SOCIETY GOVERNMENT AFFAIRS GOVERNANCE APS Sends Letter to Biden Transition Team Outlining New APS CEO: Jonathan Bagger Science Policy Priorities BY JONATHAN BAGGER BY TAWANDA W. JOHNSON Editor's note: In December, incoming APS CEO Jonathan Bagger met with PS has sent a letter to APS staff to introduce himself and President-elect Joe Biden’s answer questions. We asked him transition team, requesting A to prepare an edited version of his that he consider policy recom- introductory remarks for the entire mendations across six issue areas membership of APS. while calling for his administra- tion to “set a bold path to return the United States to its position t goes almost without saying of global leadership in science, that I am both excited and technology, and innovation.” I honored to be joining the Authored in December American Physical Society as its next CEO. I look forward to building by then-APS President Phil Jonathan Bagger Bucksbaum, the letter urges Biden matically improve the current state • Stimulus Support for Scientific on the many accomplishments of to consider recommendations in the of America’s scientific enterprise Community: Provide supple- my predecessor, Kate Kirby. But following areas: COVID-19 stimulus and put us on a trajectory to emerge mental funding of at least $26 before I speak about APS, I should back on track.
    [Show full text]
  • Thunderkat: the Meerkat Large Survey Project for Image-Plane Radio Transients
    ThunderKAT: The MeerKAT Large Survey Project for Image-Plane Radio Transients Rob Fender1;2∗, Patrick Woudt2∗ E-mail: [email protected], [email protected] Richard Armstrong1;2, Paul Groot3, Vanessa McBride2;4, James Miller-Jones5, Kunal Mooley1, Ben Stappers6, Ralph Wijers7 Michael Bietenholz8;9, Sarah Blyth2, Markus Bottcher10, David Buckley4;11, Phil Charles1;12, Laura Chomiuk13, Deanne Coppejans14, Stéphane Corbel15;16, Mickael Coriat17, Frederic Daigne18, Erwin de Blok2, Heino Falcke3, Julien Girard15, Ian Heywood19, Assaf Horesh20, Jasper Horrell21, Peter Jonker3;22, Tana Joseph4, Atish Kamble23, Christian Knigge12, Elmar Körding3, Marissa Kotze4, Chryssa Kouveliotou24, Christine Lynch25, Tom Maccarone26, Pieter Meintjes27, Simone Migliari28, Tara Murphy25, Takahiro Nagayama29, Gijs Nelemans3, George Nicholson8, Tim O’Brien6, Alida Oodendaal27, Nadeem Oozeer21, Julian Osborne30, Miguel Perez-Torres31, Simon Ratcliffe21, Valerio Ribeiro32, Evert Rol6, Anthony Rushton1, Anna Scaife6, Matthew Schurch2, Greg Sivakoff33, Tim Staley1, Danny Steeghs34, Ian Stewart35, John Swinbank36, Kurt van der Heyden2, Alexander van der Horst24, Brian van Soelen27, Susanna Vergani37, Brian Warner2, Klaas Wiersema30 1 Astrophysics, Department of Physics, University of Oxford, UK 2 Department of Astronomy, University of Cape Town, South Africa 3 Department of Astrophysics, Radboud University, Nijmegen, the Netherlands 4 South African Astronomical Observatory, Cape Town, South Africa 5 ICRAR, Curtin University, Perth, Australia 6 University
    [Show full text]
  • Plasma Modes in Surrounding Media of Black Holes and Vacuum Structure - Quantum Processes with Considerations of Spacetime Torque and Coriolis Forces
    COLLECTIVE COHERENT OSCILLATION PLASMA MODES IN SURROUNDING MEDIA OF BLACK HOLES AND VACUUM STRUCTURE - QUANTUM PROCESSES WITH CONSIDERATIONS OF SPACETIME TORQUE AND CORIOLIS FORCES N. Haramein¶ and E.A. Rauscher§ ¶The Resonance Project Foundation, [email protected] §Tecnic Research Laboratory, 3500 S. Tomahawk Rd., Bldg. 188, Apache Junction, AZ 85219 USA Abstract. The main forces driving black holes, neutron stars, pulsars, quasars, and supernovae dynamics have certain commonality to the mechanisms of less tumultuous systems such as galaxies, stellar and planetary dynamics. They involve gravity, electromagnetic, and single and collective particle processes. We examine the collective coherent structures of plasma and their interactions with the vacuum. In this paper we present a balance equation and, in particular, the balance between extremely collapsing gravitational systems and their surrounding energetic plasma media. Of particular interest is the dynamics of the plasma media, the structure of the vacuum, and the coupling of electromagnetic and gravitational forces with the inclusion of torque and Coriolis phenomena as described by the Haramein-Rauscher solution to Einstein’s field equations. The exotic nature of complex black holes involves not only the black hole itself but the surrounding plasma media. The main forces involved are intense gravitational collapsing forces, powerful electromagnetic fields, charge, and spin angular momentum. We find soliton or magneto-acoustic plasma solutions to the relativistic Vlasov equations solved in the vicinity of black hole ergospheres. Collective phonon or plasmon states of plasma fields are given. We utilize the Hamiltonian formalism to describe the collective states of matter and the dynamic processes within plasma allowing us to deduce a possible polarized vacuum structure and a unified physics.
    [Show full text]
  • Slowly Rotating Thin Shell Gravastars 2
    Slowly rotating thin shell gravastars Nami Uchikata1 and Shijun Yoshida2 1 Centro Multidisciplinar de Astrof´ısica — CENTRA, Departamento de F´ısica, Instituto Superior T´ecnico — IST, Universidade de Lisboa - UL, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal 2Astronomical Institute, Tohoku University, Aramaki-Aoba, Aoba-ku, Sendai 980-8578, Japan E-mail: [email protected], [email protected] Abstract. We construct the solutions of slowly rotating gravastars with a thin shell. In the zero-rotation limit, we consider the gravastar composed of a de Sitter core, a thin shell, and Schwarzschild exterior spacetime. The rotational effects are treated as small axisymmetric and stationary perturbations. The perturbed internal and external spacetimes are matched with a uniformly rotating thin shell. We assume that the angular velocity of the thin shell, Ω, is much smaller than the Keplerian frequency of the nonrotating gravastar, Ωk. The solutions within an accuracy up to the second order of Ω/Ωk are obtained. The thin shell matter is assumed to be described by a perfect fluid and to satisfy the dominant energy condition in the zero-rotation limit. In this study, we assume that the equation of state for perturbations is the same as that of the unperturbed solution. The spherically symmetric component of the energy density perturbations, δσ0, is assumed to vanish independently of the rotation rate. Based on these assumptions, we obtain many numerical solutions and investigate properties of the rotational corrections to the structure of the thin shell gravastar. PACS numbers: 04.70.-s arXiv:1506.06485v1 [gr-qc] 22 Jun 2015 Submitted to: Class.
    [Show full text]
  • The Collisional Penrose Process
    Noname manuscript No. (will be inserted by the editor) The Collisional Penrose Process Jeremy D. Schnittman Received: date / Accepted: date Abstract Shortly after the discovery of the Kerr metric in 1963, it was realized that a region existed outside of the black hole's event horizon where no time-like observer could remain stationary. In 1969, Roger Penrose showed that particles within this ergosphere region could possess negative energy, as measured by an observer at infinity. When captured by the horizon, these negative energy parti- cles essentially extract mass and angular momentum from the black hole. While the decay of a single particle within the ergosphere is not a particularly efficient means of energy extraction, the collision of multiple particles can reach arbitrar- ily high center-of-mass energy in the limit of extremal black hole spin. The re- sulting particles can escape with high efficiency, potentially erving as a probe of high-energy particle physics as well as general relativity. In this paper, we briefly review the history of the field and highlight a specific astrophysical application of the collisional Penrose process: the potential to enhance annihilation of dark matter particles in the vicinity of a supermassive black hole. Keywords black holes · ergosphere · Kerr metric 1 Introduction We begin with a brief overview of the Kerr metric for spinning, stationary black holes [1]. By far the most convenient, and thus most common form of the Kerr metric is the form derived by Boyer and Lindquist [2]. In standard spherical coor-
    [Show full text]
  • Arxiv:1707.03021V4 [Gr-Qc] 8 Oct 2017
    The observational evidence for horizons: from echoes to precision gravitational-wave physics Vitor Cardoso1,2 and Paolo Pani3,1 1CENTRA, Departamento de F´ısica,Instituto Superior T´ecnico, Universidade de Lisboa, Avenida Rovisco Pais 1, 1049 Lisboa, Portugal 2Perimeter Institute for Theoretical Physics, 31 Caroline Street North Waterloo, Ontario N2L 2Y5, Canada 3Dipartimento di Fisica, \Sapienza" Universit`adi Roma & Sezione INFN Roma1, Piazzale Aldo Moro 5, 00185, Roma, Italy October 10, 2017 Abstract The existence of black holes and of spacetime singularities is a fun- damental issue in science. Despite this, observations supporting their existence are scarce, and their interpretation unclear. We overview how strong a case for black holes has been made in the last few decades, and how well observations adjust to this paradigm. Unsurprisingly, we con- clude that observational proof for black holes is impossible to come by. However, just like Popper's black swan, alternatives can be ruled out or confirmed to exist with a single observation. These observations are within reach. In the next few years and decades, we will enter the era of precision gravitational-wave physics with more sensitive detectors. Just as accelera- tors require larger and larger energies to probe smaller and smaller scales, arXiv:1707.03021v4 [gr-qc] 8 Oct 2017 more sensitive gravitational-wave detectors will be probing regions closer and closer to the horizon, potentially reaching Planck scales and beyond. What may be there, lurking? 1 Contents 1 Introduction 3 2 Setting the stage: escape cone, photospheres, quasinormal modes, and tidal effects 6 2.1 Geodesics . .6 2.2 Escape trajectories .
    [Show full text]
  • Ergosphere, Photon Region Structure, and the Shadow of a Rotating Charged Weyl Black Hole
    galaxies Article Ergosphere, Photon Region Structure, and the Shadow of a Rotating Charged Weyl Black Hole Mohsen Fathi 1,* , Marco Olivares 2 and José R. Villanueva 1 1 Instituto de Física y Astronomía, Universidad de Valparaíso, Avenida Gran Bretaña 1111, Valparaíso 2340000, Chile; [email protected] 2 Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Avenida Ejército Libertador 441, Casilla 298-V, Santiago 8370109, Chile; [email protected] * Correspondence: [email protected] Abstract: In this paper, we explore the photon region and the shadow of the rotating counterpart of a static charged Weyl black hole, which has been previously discussed according to null and time-like geodesics. The rotating black hole shows strong sensitivity to the electric charge and the spin parameter, and its shadow changes from being oblate to being sharp by increasing in the spin parameter. Comparing the calculated vertical angular diameter of the shadow with that of M87*, we found that the latter may possess about 1036 protons as its source of electric charge, if it is a rotating charged Weyl black hole. A complete derivation of the ergosphere and the static limit is also presented. Keywords: Weyl gravity; black hole shadow; ergosphere PACS: 04.50.-h; 04.20.Jb; 04.70.Bw; 04.70.-s; 04.80.Cc Citation: Fathi, M.; Olivares, M.; Villanueva, J.R. Ergosphere, Photon Region Structure, and the Shadow of 1. Introduction a Rotating Charged Weyl Black Hole. The recent black hole imaging of the shadow of M87*, performed by the Event Horizon Galaxies 2021, 9, 43.
    [Show full text]
  • Black Holes from a to Z
    Black Holes from A to Z Andrew Strominger Center for the Fundamental Laws of Nature, Harvard University, Cambridge, MA 02138, USA Last updated: July 15, 2015 Abstract These are the lecture notes from Professor Andrew Strominger's Physics 211r: Black Holes from A to Z course given in Spring 2015, at Harvard University. It is the first half of a survey of black holes focusing on the deep puzzles they present concerning the relations between general relativity, quantum mechanics and ther- modynamics. Topics include: causal structure, event horizons, Penrose diagrams, the Kerr geometry, the laws of black hole thermodynamics, Hawking radiation, the Bekenstein-Hawking entropy/area law, the information puzzle, microstate counting and holography. Parallel issues for cosmological and de Sitter event horizons are also discussed. These notes are prepared by Yichen Shi, Prahar Mitra, and Alex Lupsasca, with all illustrations by Prahar Mitra. 1 Contents 1 Introduction 3 2 Causal structure, event horizons and Penrose diagrams 4 2.1 Minkowski space . .4 2.2 de Sitter space . .6 2.3 Anti-de Sitter space . .9 3 Schwarzschild black holes 11 3.1 Near horizon limit . 11 3.2 Causal structure . 12 3.3 Vaidya metric . 15 4 Reissner-Nordstr¨omblack holes 18 4.1 m2 < Q2: a naked singularity . 18 4.2 m2 = Q2: the extremal case . 19 4.3 m2 > Q2: a regular black hole with two horizons . 22 5 Kerr and Kerr-Newman black holes 23 5.1 Kerr metric . 23 5.2 Singularity structure . 24 5.3 Ergosphere . 25 5.4 Near horizon extremal Kerr . 27 5.5 Penrose process .
    [Show full text]
  • Infographic: Black Holes – Space-Time Traps
    INFOGRAPHIC BLACK HOLES – SPACE-TIME TRAPS Ergosphere Ring singularity Abstract mathematics is being used to determine the structural design of a rotating black hole. It is impossible to imagine a ring singularity with no spatial extension. Easier to envision is the event horizon; it defines the size and limit beyond which there is no return, neither for light nor matter. Everything 46 within the ergosphere has to rotate in sync with the black hole. Event horizon IMAGES GCO; ISTOCK; WEISS; (FROM TOP ESO/L. NASA/CXC/M. CALÇADA/SPACEENGINE.ORG TO BOTTOM) An incredible thought experiment: compress the Earth to the size of a cherry and you turn it into a black hole. THEORY In 1783, John Michell first imagined In 1915, Albert Einstein created the mathematical basis for “dark stars”, which do not emit such objects in his general theory of relativity. A year later, light because of their gravitation. Karl Schwarzschild described the geometry of a static black hole. OBSERVATION In the early 1970s, the first stellar black Groups led by Andrea Ghez (University of hole (Cygnus X-1) was discovered as California, Los Angeles) and Reinhard Genzel part of a binary star system. This was (Max Planck Institute for Extraterrestrial accomplished indirectly with the aid of Physics) had been observing the orbits of stars an X-ray satellite, which registered at the center of our Milky Way since the high-energy radiation from the hot gas 1990s and concluded the existence of a black disk (accretion disk) surrounding the hole of 4.3 million solar masses, for which black hole.
    [Show full text]
  • Arxiv:2102.11209V2 [Physics.Hist-Ph] 4 Mar 2021 Em Fanwtemlrdainmcaim(Eto 14)
    Demons in Black Hole Thermodynamics: Bekenstein and Hawking Galina Weinstein∗ The Department of Philosophy, University of Haifa, Haifa, the Interdisciplinary Center (IDC), Herzliya, Israel. March 3, 2021 Abstract This paper comprehensively explores Stephen Hawking’s interaction with Jacob Bekenstein. Both Hawking and Bekenstein benefited from the interaction with each other. It is shown that Hawking’s interaction with Bekenstein drove him to solve the problems in Bekenstein’s black hole thermodynamics in terms of a new thermal radiation mechanism. Hawking argued that Bekenstein’s thermodynamics of black holes was riddled with problems. In trying to solve these problems, Hawking cut the Gordian knot with a single stroke: black holes emit thermal radiation. Hawking derived the thermal radiation using a semi-classical approxima- tion in which the matter fields are treated quantum mechanically on a classical space-time background. Hawking’s semi-classical approximation yielded a simple formula for the entropy of the black hole, which turned out to be equivalent to Bekenstein’s equation for entropy. 1 Preface This paper comprehensively explores Stephen Hawking’s interaction with Jacob Bekenstein. I show in this paper that both Hawking and Bekenstein benefited from the interaction with each other. Bekenstein ascribed entropy to black holes and suggested that the entropy arXiv:2102.11209v2 [physics.hist-ph] 4 Mar 2021 of black holes is proportional to the surface area of the event horizon of the black hole (Section 6). Hawking proposed an area theorem, which suggested to Bekenstein that the black hole entropy should tend to grow (Section 4). It is shown in this paper that Hawking’s interaction with Bekenstein drove the former to solve the problems in Bekenstein’s black hole thermodynamics in terms of a new thermal radiation mechanism (Section 14).
    [Show full text]
  • Simulating the Dynamics of Supermassive Black Holes
    Master’s thesis Astronomy Simulating the dynamics of supermassive black holes Vili Oskari Oja December 6, 2019 Supervisors: Professor Peter Johansson Dr. Pauli Pihajoki Reviewers: Professor Peter Johansson Dr. Pauli Pihajoki UNIVERSITY OF HELSINKI Department of Physics PL 64 (Gustaf Hällströmin katu 2) 00014 Helsingin yliopisto Finland HELSINGIN YLIOPISTO — HELSINGFORS UNIVERSITET — UNIVERSITY OF HELSINKI Tiedekunta — Fakultet — Faculty Laitos — Institution — Department Faculty of Science Department of Physics Tekijä — Författare — Author Vili Oskari Oja Työn nimi — Arbetets titel — Title Simulating the dynamics of supermassive black holes Oppiaine — Läroämne — Subject Astronomy Työn laji — Arbetets art — Level Aika — Datum — Month and year Sivumäärä — Sidoantal — Number of pages Master’s thesis December 6, 2019 88 pages Tiivistelmä — Referat — Abstract It is widely believed that most galaxies in our Universe have a supermassive black hole in their center. Black holes play an important role in the evolution of galaxies, and they can offer us a unique way to observe the Universe through gravitational waves. In this Master’s thesis I have reviewed the basic properties of black holes and summarized several numerical and computational methods used in simulating the dynamics of black holes at a very high accuracy. One of these methods is the post-Newtonian (PN) expansion, which is a way of approximating the effects of general relativity by adding additional terms to the Newtonian equations of motion, without having to perform challenging full relativistic simulations. I have also simulated two different types of scenarios involving supermassive black holes. First, I have simulated mergers of different black hole binaries to test the effects of the different orders of PN expansion terms on the evolution and lifetime of the system.
    [Show full text]
  • The Astrophysical Signatures of Black Holes: the Horizon, the ISCO, the Ergosphere and the Light Circle
    The astrophysical signatures of black holes: the horizon, the ISCO, the ergosphere and the light circle Marek A. Abramowicz Abstract Three advanced instruments planned for a near future (LOFT, GRAVITY, THE EVENT HORIZON TELESCOPE) provide unprecedented angular and time reso- lutions, which allow to probe regions in the immediate vicinity of black holes. We may soon be able to search for the signatures of the super-strong gravity that is characteristic to black holes: the event horizon, the ergosphere, the innermost stable circular orbit (ISCO), and the photon circle. This review discusses a few fundamen- tal problems concerning these theoretical concepts. 1 Introduction Undoubtedly, the existence of black holes is one of a few most bizarre predictions ever made in the whole acts of physics. The existence of massive objects with gravity strong enough to prevent light from escaping their surfaces was anticipated already in the XVIII century by John Mitchel, and later but independently by Pierre-Simon Laplace. However, the fundamental properties of black holes have been discovered, understood and described in terms of brilliant mathematical developments of Al- Marek A. Abramowicz Nicolaus Copernicus Astronomical Center, ul. Bartycka 18, 00-716 Warszawa, Poland; Physics Department, Silesian University (Opava), Institute of Astronomy (Prague), The Czech Republic; Professor Emeritus at the Department of Physics, University of Gothenburg, Sweden, e-mail: [email protected] 1 2 Marek A. Abramowicz bert Einstein’s general theory of relativity, only much later — indeed in our times1. Astrophysically, the most important of these fundamental properties are2: 1. Event horizon: This may be imagined as a sphere (but not as a rigid surface) 2 with the “gravitational radius” rG ∼ GM=c surrounding the black hole of the mass M, from within which nothing may emerge.
    [Show full text]