DOCSLIB.ORG

Phys133 Sample Midterm #2 Covers Chs.10-13

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Phys133 Sample Midterm #2 Covers Chs.10-13 Phys133 Sample MidTerm #2 Covers Chs.10-13 Name___________________________________ MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) What is the Sun made of? 1) A) 98 percent hydrogen, 2 percent helium and other elements B) 50 percent hydrogen, 25 percent helium, 25 percent other elements C) 100 percent hydrogen and helium D) 70 percent helium, 28 percent hydrogen, 2 percent other elements E) 70 percent hydrogen, 28 percent helium, 2 percent other elements 2) Using groud-based telescop;es, the most distant stars we can measure stellar parallax for are 2) approximately A) 100 parsecs away. B) 5 parsecs away. C) 10,000 parsecs away. D) in the Andromeda Galaxy. E) halfway across the Milky Way Galaxy. 3) Which of the following statements comparing open and globular star clusters is not true? 3) A) Stars in open clusters are relatively young while stars in globular clusters are very old. B) For both open and globular clusters, we can assume that all the stars in a particular cluster are about the same age. C) Open clusters are found only in the disk of the galaxy while globular clusters may be found both in the disk and the halo of the galaxy. D) Open and globular clusters each typically contain a few hundred stars. 4) What happens when a star exhausts its core hydrogen supply? 4) A) It contracts, becoming hotter and brighter. B) Its core contracts, but its outer layers expand and the star becomes bigger but cooler and therefore remains at the same brightness. C) It expands, becoming bigger but dimmer. D) It contracts, becoming smaller and dimmer. E) Its core contracts, but its outer layers expand and the star becomes bigger and brighter. 5) What is a protostar? 5) A) a star that has planets B) a star that is still in the process of forming C) a star in its final stage of life D) an intermediate-mass star 1 6) What kind of star is most likely to become a white-dwarf supernova? 6) A) a white dwarf star with a red giant binary companion B) a star like our Sun C) a binary M star D) a pulsar E) an O star 7) From the center outward, which of the following lists the "layers" of the Sun in the correct order? 7) A) core, corona, radiation zone, convection zone, photosphere, chromosphere B) core, convection zone, radiation zone, photosphere, chromosphere, corona C) core, convection zone, radiation zone, corona, chromosphere, photosphere D) core, radiation zone, convection zone, photosphere, chromosphere, corona E) core, radiation zone, convection zone, corona, chromosphere, photosphere 8) When is/was gravitational contraction an important energy generation mechanism for the Sun? 8) A) It is important during periods when the Sun is going from solar maximum to solar minimum. B) It is the primary energy generation mechanism in the Sun today. C) It has played a role throughout the Sun's history, but it was most important right after nuclear fusion began in the Sun's core. D) It was important when the Sun was forming from a shrinking interstellar cloud of gas. 9) How is the lifetime of a star related to its mass? 9) A) More massive stars live slightly longer lives than less massive stars. B) More massive stars live considerably shorter lives than less massive stars. C) More massive stars live considerably longer lives than less massive stars. D) More massive stars live slightly shorter lives than less massive stars. 10) Why did the solar nebula heat up as it collapsed? 10) A) The shock wave from a nearby supernova heated the gas. B) As the cloud shrank, its gravitational potential energy was converted to kinetic energy and then into thermal energy. C) Radiation from other nearby stars that had formed earlier heated the nebula. D) Collisions among planetesimals generated friction and heat. E) Nuclear fusion occurring in the core of the protosun produced energy that heated the nebula. 2 Refer to the labels (a) through (e) on the following sketch of an H–R diagram. 11) Which group represents stars that are cool and dim? 11) A) A B) B C) C D) D E) E 12) Which of the following is closest in size (radius) to a white dwarf? 12) A) a small city B) the Sun C) the earth D) a basketball E) a football stadium 13) After a massive-star supernova, what is left behind? 13) A) always a white dwarf B) always a black hole C) always a neutron star D) either a neutron star or a black hole E) either a white dwarf or a neutron star 14) What types of stars end their lives with supernovae? 14) A) stars that are at least several times the mass of the Sun B) stars that have reached an age of 10 billion years C) all stars that are yellow in color D) stars that are similar in mass to the Sun E) all stars that are red in color 15) On a Hertzsprung-Russell diagram, where would we find stars that have the largest radii? 15) A) lower right B) upper right C) upper left D) lower left 16) Which element has the lowest mass per nuclear particle and therefore cannot release energy by 16) either fusion or fission? A) iron B) silicon C) hydrogen D) oxygen E) uranium 3 17) What is a planetary nebula? 17) A) the expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star B) the molecular cloud from which protostars form C) what is left of the planets around a star after a low-mass star has ended its life D) the expanding shell of gas that is left when a white dwarf explodes as a supernova E) a disk of gas surrounding a protostar that may form into planets 18) How many helium nuclei fuse together when making carbon? 18) A) 4 B) 3 C) 2 D) varies depending on the reaction E) none of the above 19) When does a star become a main-sequence star? 19) A) when a star becomes luminous enough to emit thermal radiation B) when the protostar assembles from a molecular cloud C) when hydrogen fusion is occurring throughout a star's interior D) the instant when hydrogen fusion first begins in the star's core E) when the rate of hydrogen fusion within the star's core is high enough to sustain gravitational equilibrium 20) No stars have been found with masses greater than 200-300 times our Sun because 20) A) they would generate so much power that they would blow themselves apart. B) molecular clouds do not have enough material to form such massive stars. C) they are not bright enough to be seen nearby. D) they would fragment into binary stars because of their rapid rotation. E) they shine exclusively at X-ray wavelengths and become difficult to detect. 21) Cluster ages can be determined from 21) A) spectroscopic binaries. B) main sequence fitting. C) visual binaries. D) main sequence turnoff. E) pulsating variable stars. 22) Suppose you see two main-sequence stars of the same spectral type. Star 1 is dimmer in apparent 22) brightness than Star 2 by a factor of 100. What can you conclude? (Neglect any effects that might be caused by interstellar dust and gas.) A) Without first knowing the distances to these stars, you cannot draw any conclusions about how their true luminosities compare to each other. B) The luminosity of Star 1 is a factor of 100 less than the luminosity of Star 2. C) Star 1 is 100 times nearer than Star 2. D) Star 1 is 10 times more distant than Star 2. E) Star 1 is 100 times more distant than Star 2. 4 23) Suppose you measure the parallax angle for a particular star to be 0.1 arcsecond. The distance to 23) this star is A) 0.1 light-year. B) 0.1 parsec. C) 10 parsecs. D) 10 light-years. E) impossible to determine. 24) If the distance between us and a star is doubled, with everything else remaining the same, the 24) luminosity A) remains the same, but the apparent brightness is decreased by a factor of four. B) is decreased by a factor of four, but the apparent brightness remains the same. C) is decreased by a factor of four, and the apparent brightness is decreased by a factor of four. D) remains the same, but the apparent brightness is decreased by a factor of two. E) is decreased by a factor of two, and the apparent brightness is decreased by a factor of two. 25) A star's luminosity is the 25) A) lifetime of the star. B) total amount of light energy that the star radiates per unit time. C) surface temperature of the star. D) apparent brightness of the star in our sky. E) total amount of light that the star will radiate over its entire lifetime. 26) Since all stars begin their lives with the same basic composition, what characteristic most 26) determines how they will differ? A) time they are formed B) location where they are formed C) luminosity they are formed with D) color they are formed with E) mass they are formed with 27) How do we know what goes on under the surface of the Sun? 27) A) We have X-ray images from satellites of the interior of the Sun. B) Astronomers create mathematical models that use the laws of physics, the Sun's observed composition and mass, and computers to predict internal conditions.
Load more

Recommended publications
  • Institute for Nuclear Study University of Tokyo Tanashi, Tokyo 188, Japan And
    lNS-Rep.-645 INSTITUTE FOR NUCLEAR STUDY . UNIVERSITY OF TOKYO Sept 1987 Tanashi, Tokyo 188 Japan Resonant Spin-Flavor Precession of k Solar and Supernova Neutrinos Chong-Sa Lim and William J. Marciano •3300032376 INS-Rep.-645 Sept. 1987 Resonant Spin-Flavor Precession of Solar and Supernova Neutrinos Chong-Sa Lin Institute for Nuclear Study University of Tokyo Tanashi, Tokyo 188, Japan and William J. Mareiano Brookharen National Laboratory Upton. New Kork 11973, U.S.A. Abstract: The combined effect of natter and aagnetic fields on neutrino spin and flavor precession is examined. We find a potential new kind of resonant solar neutrino conversion \>_ * eL v or vT (for Dirac neutrinos) or «e *• « or vT (for Hajorana R R neutrinos). Such a resonance could help account for the lower than' expected solar neutrino v flux and/or Indications of an antl-oorrelatlon between fluctuations in the v( flux and sunspot activity. Consequences of spin-flavor precession for supernova neutrinos are also briefly discussed. - 1 - There has been a longstanding disagreement between the solar neutrino v_ flux monitored by B. Davis"" and collaborators Average Flux - 2.1 i 0.3 SHU , (1) (1 SNU - 10*' captures/s-atom) 7 37 via the reaction \>e • ' Cl •• «" • Ar and Bahcall'a standard solar model prediction Predicted Flux - 7.9 ± 2.5 SNU <3o errors) . <2) That discrepancy has come to be known as the solar neutrino puzzle. Attempts to resolve It have given rise to many speculative Ideas about unusual properties of neutrinos and/or the solar interior. One rather recently proposed solution, the MSW"-' (Mlkheyev, Snlrnov, Wolfensteln) effect is particularly elegant.
    [Show full text]
  • Doc.10100.Space Weather Manual FINAL DRAFT Version
    Doc 10100 Manual on Space Weather Information in Support of International Air Navigation Approved by the Secretary General and published under his authority First Edition – 2018 International Civil Aviation Organization TABLE OF CONTENTS Page Chapter 1. Introduction ..................................................................................................................................... 1-1 1.1 General ............................................................................................................................................... 1-1 1.2 Space weather indicators .................................................................................................................... 1-1 1.3 The hazards ........................................................................................................................................ 1-2 1.4 Space weather mitigation aspects ....................................................................................................... 1-3 1.5 Coordinating the response to a space weather event ......................................................................... 1-3 Chapter 2. Space Weather Phenomena and Aviation Operations ................................................................. 2-1 2.1 General ............................................................................................................................................... 2-1 2.2 Geomagnetic storms ..........................................................................................................................
    [Show full text]
  • Stability of Toroidal Magnetic Fields in Rotating Stellar Radiation Zones
    A&A 478, 1–8 (2008) Astronomy DOI: 10.1051/0004-6361:20077172 & c ESO 2008 Astrophysics Stability of toroidal magnetic fields in rotating stellar radiation zones L. L. Kitchatinov1,2 and G. Rüdiger1 1 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482, Potsdam, Germany e-mail: [lkitchatinov;gruediger]@aip.de 2 Institute for Solar-Terrestrial Physics, PO Box 291, Irkutsk 664033, Russia e-mail: [email protected] Received 26 January 2007 / Accepted 14 October 2007 ABSTRACT Aims. Two questions are addressed as to how strong magnetic fields can be stored in rotating stellar radiation zones without being subjected to pinch-type instabilities and how much radial mixing is produced if the fields are unstable. Methods. Linear equations are derived for weak disturbances of magnetic and velocity fields, which are global in horizontal dimen- sions but short–scaled in radius. The linear formulation includes the 2D theory of stability to strictly horizontal disturbances as a special limit. The eigenvalue problem for the derived equations is solved numerically to evaluate the stability of toroidal field patterns with one or two latitudinal belts under the influence of rigid rotation. Results. Radial displacements are essential for magnetic instability. It does not exist in the 2D case of strictly horizontal disturbances. Only stable (magnetically modified) r-modes are found in this case. The instability recovers in 3D. The minimum field strength Bmin for onset of the instability and radial scales of the most rapidly growing modes are strongly influenced by finite diffusion, the scales are indefinitely short if diffusion is neglected. The most rapidly growing modes for the Sun have radial scales of about 1 Mm.
    [Show full text]
  • The Sun: Our Star (Chapter 14) Based on Chapter 14
    The Sun: Our Star (Chapter 14) Based on Chapter 14 • No subsequent chapters depend on the material in this lecture • Chapters 4, 5, and 8 on “Momentum, energy, and matter”, “Light”, and “Formation of the solar system” will be useful for understanding this chapter. Goals for Learning • What is the Sun’s structure? • How does the Sun produce energy? • How does energy escape from the Sun? • What is solar activity? What Makes the Sun Shine? • Sun’s size/distance known by 1850s • Some kind of burning, chemical reaction? – Can’t provide enough energy • Gravitational potential energy from contraction? – Sun doesn’t shrink very fast, shines for 25 million years • Physicists like this idea. Geologists don’t, because rocks/fossils suggest age of 100s of millions of years E=mc2 (1905, Einstein) • Massive Sun has enough energy to shine for billions of years, geologists are happy • But how does “m” become “E”? Sun is giant ball of plasma (ionized gas) Charged particles in plasma are affected by magnetic fields Magnetic fields are very important in the Sun Sun = 300,000 ME Sun >1000 MJ Radius = 700,000 km Radius > 100 RE 3.8 x 1026 Watts Rotation: 25 days (Equator) Rotation: 30 days (Poles) Surface T = 5,800 K Core T = 15 million K 70% Hydrogen, 28% Helium, 2% heavier elements Solar Wind • Stream of charged particles blown continually outwards from Sun • Shapes the magnetospheres of the planets today • Cleared away the gas of the solar nebula 4.5 billion years ago Corona • Low density outer layer of Sun’s atmosphere • Extends several million km high • T = 1 million K (why?) • Source of solar X-ray emissions – what wavelength? X-ray image of solar corona.
    [Show full text]
  • Chapter 15--Our
    2396_AWL_Bennett_Ch15/pt5 6/25/03 3:40 PM Page 495 PART V STELLAR ALCHEMY 2396_AWL_Bennett_Ch15/pt5 6/25/03 3:40 PM Page 496 15 Our Star LEARNING GOALS 15.1 Why Does the Sun Shine? • Why was the Sun dimmer in the distant past? • What process creates energy in the Sun? • How do we know what is happening inside the Sun? • Why does the Sun’s size remain stable? • What is the solar neutrino problem? Is it solved ? • How did the Sun become hot enough for fusion 15.4 From Core to Corona in the first place? • How long ago did fusion generate the energy we 15.2 Plunging to the Center of the Sun: now receive as sunlight? An Imaginary Journey • How are sunspots, prominences, and flares related • What are the major layers of the Sun, from the to magnetic fields? center out? • What is surprising about the temperature of the • What do we mean by the “surface” of the Sun? chromosphere and corona, and how do we explain it? • What is the Sun made of? 15.5 Solar Weather and Climate 15.3 The Cosmic Crucible • What is the sunspot cycle? • Why does fusion occur in the Sun’s core? • What effect does solar activity have on Earth and • Why is energy produced in the Sun at such its inhabitants? a steady rate? 496 2396_AWL_Bennett_Ch15/pt5 6/25/03 3:40 PM Page 497 I say Live, Live, because of the Sun, from some type of chemical burning similar to the burning The dream, the excitable gift.
    [Show full text]
  • Radiation Zone
    AST 100 General Astronomy: 5. What’s inside the Sun? Stars & Galaxies From the Center Outwards • Core: Hydrogen fusing into helium, releasing energy in ANNOUNCEMENTS the form of gamma rays, neutrinos, and positrons Midterm I on Tue, Sept. 29 it will cover class material up to today (included) • Core temp = 15 million K, hot & dense from the gravitational Quiz #2 today, end of class weight of all that mass Meanderings of outbound photons Our gamma-ray photons random walk outwards (getting Radiation Zone redirected with every step), gradually cooling • Gamma ray photons leave the core and move into an area known as the Takes hundreds of Radiation Zone thousands to a million – Neutrinos? They leave right years to get out!! away, no interaction – Positrons? Quickly find electrons in the core to annihilate with. • Photons only travel about 1 mm before being redirected in another direction T=10 million K. Photosphere Convection Zone • At the top of the convection • Eventually, gas is cool zone, the densities are now enough (2 million K at the low enough that our boundary) and becomes photons can zoom away. turbulent – Now downgraded all the – No longer just redirects way to visible energies photons, now absorbs them • Photosphere is the “visible surface” of the Sun • Convection: hotter • T = only 5800 K regions rise, cooler • Photons free - seen at Earth regions sink 8 min later • Blackbody spectrum (T= • Energy continues to work 5800 K) + absorption from its way out - nearly 1 cooler gasses just on top million years to get out Granulation: turbulent convection Granulation Movie Appearance of the photosphere • Typical granulations last only 8 - 15 minutes • Movie covers 35 min Taken by G.
    [Show full text]
  • The Sun Worksheet
    Name ____________________________ Date ____________________ Class ____________ The Solar System The Sun Guide for Reading ■ What are the three layers of the sun’s interior? ■ What are the three layers of the sun’s atmosphere? ■ What features form on or above the sun’s surface? The sun’s mass is 99.8 percent of all the mass in the solar system. Because the sun is so large, its gravity is strong enough to hold all of the planets and other distant objects in orbit. Unlike Earth, the sun does not have a solid surface. Like Earth, the sun has an interior and an atmosphere. The sun’s interior consists of the core, radiation zone, and convection zone. Each layer has different properties. The sun produces an enormous amount of energy in its core, or central region. The sun’s energy comes from nuclear fusion. In the process of nuclear fusion, hydrogen atoms in the sun join to form helium. The light and heat produced by the sun’s core first pass through the middle layer of the sun’s interior, the radiation zone. The radiation zone is a region of very tightly packed gas where energy is transferred mainly in the form of electromagnetic radiation. The convection zone is the outermost layer of the sun’s interior. Hot gases rise from the bottom of the convection zone and gradually cool as they approach the top. Cooler gases sink, forming loops of gas that move heat toward the sun’s surface. The sun’s atmosphere consists of the photosphere, the chromosphere, and the corona.
    [Show full text]
  • Dynamics of the Earth's Radiation Belts and Inner Magnetosphere Newfoundland and Labrador, Canada 17 – 22 July 2011
    AGU Chapman Conference on Dynamics of the Earth's Radiation Belts and Inner Magnetosphere Newfoundland and Labrador, Canada 17 – 22 July 2011 Conveners Danny Summers, Memorial University of Newfoundland, St. John's (Canada) Ian Mann, University of Alberta, Edmonton (Canada) Daniel Baker, University of Colorado, Boulder (USA) Program Committee David Boteler, Natural Resources Canada, Ottawa, Ontario (Canada) Sebastien Bourdarie, CERT/ONERA, Toulouse (France) Joseph Fennell, Aerospace Corporation, Los Angeles, California (USA) Brian Fraser, University of Newcastle, Callaghan, New South Wales (Australia) Masaki Fujimoto, ISAS/JAXA, Kanagawa (Japan) Richard Horne, British Antarctic Survey, Cambridge (UK) Mona Kessel, NASA Headquarters, Washington, D.C. (USA) Craig Kletzing, University of Iowa, Iowa City (USA) Janet Kozy ra, University of Michigan, Ann Arbor (USA) Lou Lanzerotti, New Jersey Institute of Technology, Newark (USA) Robyn Millan, Dartmouth College, Hanover, New Hampshire (USA) Yoshiharu Omura, RISH, Kyoto University (Japan) Terry Onsager, NOAA, Boulder, Colorado (USA) Geoffrey Reeves, LANL, Los Alamos, New Mexico (USA) Kazuo Shiokawa, STEL, Nagoya University (Japan) Harlan Spence, Boston University, Massachusetts (USA) David Thomson, Queen's University, Kingston, Ontario (Canada) Richard Thorne, Univeristy of California, Los Angeles (USA) Andrew Yau, University of Calgary, Alberta (Canada) Financial Support The conference organizers acknowledge the generous support of the following organizations: Cover photo: Andy Kale ([email protected])
    [Show full text]
  • The Science of the Sun by Cindy Grigg
    The Science of the Sun By Cindy Grigg 1 Photo credit: NASA 2 Our sun is a star. Like all stars, it is a mass of very hot gases. On Earth, burning fossil fuels like gasoline or coal gives us energy for our cars and heating our homes. But the sun's energy doesn't come from burning fuels. The sun's energy comes from nuclear fusion. The nuclei (plural form of nucleus) of different atoms of gases in the sun fuse or join together. Most of the sun's fusion happens when atoms of hydrogen smash into each other. Under high pressure and at high temperatures, the atoms join or fuse together. This creates helium atoms. Every atom releases heat and light when it fuses with another atom. 3 How big is the sun? Its diameter, the distance across its center, is about 870,000 miles. That's more than one hundred times the diameter of Earth. The sun's volume is more than a million times the volume of Earth. Another way to say this is that the sun could hold one million Earths inside it. 4 The sun has different layers of gases. Each layer blends into the next, like the layers of Earth's atmosphere. The core is the center of the sun. Most of the sun's mass is in its core. The core is extremely dense. It is also very hot. Almost all fusion takes place in the core. 5 Energy created in the core moves outward. It passes next into the radiative or radiation zone.
    [Show full text]
  • 8. the Sun As a Star
    Astronomy 110: SURVEY OF ASTRONOMY 8. The Sun as a Star 1. Inside the Sun 2. Solar Energy 3. Solar Activity The Sun is not only the largest object in our solar system — it is also the nearest example of a star. It produces energy by converting hydrogen to helium, thereby maintaining a constant internal temperature. Particles emitted by the Sun and detected on Earth confirm the details of this picture. Radius: 6.9 × 108 m (109 times Earth) Mass: 2 × 1030 kg (300,000 Earths) Luminosity: 3.8 × 1026 watts Copyright © 2009 Pearson Education, Inc. Composition of the Sun Number of Chemical Atomic Atomic Atoms Symbol Number Weight 1,000,000 H 1 1 85,000 He 2 4 850 O 8 16 400 C 6 12 120 Ne 10 20 100 N 7 14 47 Fe 26 56 1. INSIDE THE SUN a. How Does the Sun Stay Hot? b. Two Kinds of Equilibrium c. Structure of the Sun How Does the Sun Stay Hot? Why does the Sun shine? Because it is hot! Copyright © 2009 Pearson Education, Inc. Is it on FIRE? … NO! Chemical Energy Content ~ 10,000 years Luminosity Copyright © 2009 Pearson Education, Inc. Is it CONTRACTING? … NO! Gravitational Potential Energy ~ 25 million years Luminosity Copyright © 2009 Pearson Education, Inc. E = mc2 —Einstein, 1905 It is powered by NUCLEAR ENERGY! Nuclear Potential Energy (core) ~ 10 billion years Luminosity Copyright © 2009 Pearson Education, Inc. Energy From Matter Matter is frozen energy, and each can be converted to the other. The “rate of exchange” is E = mc2 where c = 3 × 105 km/s is the speed of light.
    [Show full text]
  • Chapter 11: Our Star
    Lecture Outline Chapter 11: Our Star © 2015 Pearson Education, Inc. Why does the Sun shine? © 2015 Pearson Education, Inc. Is it on FIRE? … NO! Chemical Energy Content ~ 10,000 years Luminosity © 2015 Pearson Education, Inc. Is it CONTRACTING? … NO! Gravitational Potential Energy ~ 25 million years Luminosity © 2015 Pearson Education, Inc. E = mc2 —Einstein, 1905 It is powered by NUCLEAR ENERGY! Nuclear Potential Energy (core) ~ 10 billion years Luminosity © 2015 Pearson Education, Inc. Gravitational equilibrium: Gravity pulling in balances pressure pushing out. © 2015 Pearson Education, Inc. Energy balance: Thermal energy released by fusion in core balances radiative energy lost from surface. © 2015 Pearson Education, Inc. Gravitational contraction… provided energy that heated the core as the Sun was forming. Contraction stopped when fusion started replacing the energy radiated into space. © 2015 Pearson Education, Inc. What is the Sun's structure? © 2015 Pearson Education, Inc. 11.2 Nuclear Fusion in the Sun Our goals for learning: • How does nuclear fusion occur in the Sun? • How does the energy from fusion get out of the Sun? • How do we know what is happening inside the Sun? © 2015 Pearson Education, Inc. Fission Fusion Big nucleus splits into Small nuclei stick together smaller pieces. to make a bigger one. (Nuclear power plants) (Sun, stars) © 2015 Pearson Education, Inc. High temperatures enable nuclear fusion to happen in the core. © 2015 Pearson Education, Inc. The Sun releases energy by fusing four hydrogen nuclei into one helium nucleus. © 2015 Pearson Education, Inc. IN 4 protons OUT 4He nucleus 2 gamma rays 2 positrons 2 neutrinos Total mass is 0.7% lower.
    [Show full text]
  • Neutron Star
    Chapter 10 Our Star X-ray visible Radius: 6.9 108 m (109 times Earth) Mass: 2 1030 kg (300,000 Earths) Luminosity: 3.8 1026 watts (more than our entire world uses in 1 year!) Why does the Sun shine? Is it on FIRE? Is it on FIRE? Chemical Energy Content (J) ~ 10,000 years Luminosity (J/s = W) Is it on FIRE? … NO Chemical Energy Content ~ 10,000 years Luminosity Is it CONTRACTING? Is it CONTRACTING? Gravitational Potential Energy ~ 25 million years Luminosity Is it CONTRACTING? … NO Gravitational Potential Energy ~ 25 million years Luminosity E = mc2 —Einstein, 1905 It is powered by NUCLEAR ENERGY! Nuclear Potential Energy (core) ~ 10 billion years Luminosity E = mc2 —Einstein, 1905 It is powered by NUCLEAR ENERGY! •Nuclear reactions generate the Sun’s heat •But they require very high temperatures to begin with •Where do those temperatures come from? •They come from GRAVITY! •The tremendous weight of the Sun’s upper layers compresses interior •The intense compression generates temperatures >107 K in the innermost core •And that’s where the nuclear reactions are Gravitational Equilibrium •The compression inside the Sun generates temperatures that allow fusion •The fusion reactions in turn generate outward pressure that balances the inward crush of gravity •The Sun is in a balance between outward pressure from fusion and inward pressure from gravity •This is called gravitational equilibrium The Sun’s Structure Solar wind: A flow of charged particles from the surface of the Sun Corona: Outermost layer of solar atmosphere Temp ~1 million
    [Show full text]