Photodissociation Regions Radiative Transfer. Dr. Thomas G. Bisbas
|
|
- Rosamond Clark
- 5 years ago
- Views:
Transcription
1 Photodissociation Regions Radiative Transfer Dr. Thomas G. Bisbas
2 Interstellar Radiation Field In the solar neighbourhood, the ISRF is dominated by six components Schematic sketch of the energy density of the interstellar radiation field at different frequencies.
3 Structure of ionized regions Ionized gas Ionization Front Molecular Gas Massive Stars Molecular Gas Kallias Ioannidis
4 Photodissociation Regions The region where the atomic phase occurs is known as Photodissociation Region (PDR). Studying PDRs is a key aspect to understand the role played by the FUV radiation (6eV < hν < 13.6eV) in governing the physical and chemical structure and determining the thermal balance of the neutral ISM in galaxies.
5 Photodissociation Regions The source of FUV photons need not be restricted to stars. The accretion of material onto supermassive black holes in active galactic nuclei (AGN) produces strong ultraviolet and often X-ray emission that impacts the surrounding gas and dust, creating large PDRs. Supernova explosions also enrich the surrounding ISM with metals thus changing its metallicity and therefore the overall gas and dust temperature profiles. Examining such extreme environments can provide insight into the dynamics of non-local ISM observed at the centres of merger and starburst galaxies.
6 Molecular hydrogen in the Universe The bulk of baryonic non-stellar mass of the Universe consists of hydrogen with a total fractional abundance of ~70%. It is the gas that regulates the evolution of galaxies across the epoch times. Molecular hydrogen is responsible for star formation and in general plays a fundamental role in many astrophysical contexts. It is found in all cold (T~10K) and dark regions where UV photons emitted by stars do not penetrate.
7 Molecular hydrogen in the Universe Molecular hydrogen is not visible in optical wavelengths and does not emit radiation which can be captured by radio telescopes. In particular it lacks a permanent dipole moment and can only change ro-vibrational state through weak quadrupolar transition with high excitation temperatures >500 K that are sub-thermally populated and so difficult to detect in the cold bulk of the ISM. The pure rotational transitions of molecular hydrogen lie at mid-infrared wavelengths that are largely inaccessible from the ground, due to telluric absorption and strong background radiation. Because of this, we observe molecular hydrogen indirectly using carbon monoxide as a tracer. CO is also abundant in the Universe and it formed in places where molecular hydrogen is also formed. It also emits radiation detectable by radiotelescopes such as ALMA, JCMT, VLA etc.
8 Heating mechanisms in diffuse clouds The hydrogen that is found deep inside Diffuse Clouds is almost entirely neutral. Even if an OB star (or stars) were nearby, no UV photons at wavelengths less than 912A can penetrate deep into these diffuse clouds, since (by definition) they will have all been used up in ionising the hydrogen found in the outer edge of the cloud. Thus deep in these diffuse clouds we cannot invoke hydrogen photoionisation as the main heating mechanism. Only atoms with ionization potentials less than 13.6eV can be ionised, by the remaining lower energy photons
9 Heating mechanisms in diffuse clouds Hydrog en Helium Carbon Nitroge n Oxygen Hydrogen has an ionization potential of 13.6eV Helium (the next most abundant element) has ionization potential higher than for hydrogen (24eV for neutral HeI and 54eV for HeII), so photoionisation of this element is impossible in the interior of a diffuse cloud. OI has ionization potential of 13.6eV (very very close to the hydrogen one) and NI has 14.4eV, so again these elements are unsuitable to be photoionized in the innermost part of a diffuse cloud. However, neutral carbon (CI) has lower ionization potential (11.3eV, corresponding to a wavelength of 1110A), so potentially photoionisation of CI could provide kinetic energy of photoelectrons which could heat the gas.
10 Photoelectric effect The photoelectric effect is the effect at which metals emit electrons when light shines upon them. Electrons emitted in this manner may be called photoelectrons. It was first proposed by Albert Einstein in 1905 who was awarded the Nobel Prize in 1921 for that. The reason behind this award is that it is the first experiment which showed that the light apart from wave can also behave as a particle, or as a discrete wave packet (a photon) carrying energy E=hf (h is Planck's constant, f is the frequency).
11 Photoelectric heating The main heating process for the deep layers within the diffuse ISM is the ejection of photoelectrons from the small dust grains that exist with the gas. Such grains have a relatively low work function (analogous to atomic ionization potential energy), denoted W. The energy E of the ejected electron is thus: Far-ultraviolet photons absorbed by a grain will create energetic (several ev) electrons. E = hv W h is Planck's constant, v is photon's frequency While these electrons diffuse in the grain, they will lose energy through collisions. However, if during this diffusion process they reach the surface with enough energy to overcome the work function W of the grain, and the Coulomb potential φ (if the grain is positively charged), they can be injected into the gas phase with excess kinetic energy.
12 Photoelectric heating Polycyclic Aromatic Hydrocarbons (PAH) are large molecules, organic compounds, which contain only carbon and hydrogen. It has been suggested that they have been formed as early as the first couple of billions of years after the Big Bang, in association with the formation of new stars and exoplanets. It is also suggested that PAHs account for significant percentage of all carbon in the Universe, and that they are potential sites for abiologic syntheses of materials required by the earliest forms of life. The photoelectric heating due to PAHs is more efficient than grains, as the electrons do not suffer collisions once they absorb an FUV photon.
13
14 Photon heating by H 2 After photodissociation of a molecule, the fragments will carry away some of the photon energy as kinetic energy, heating the gas. After (re-)formation of a molecule, the newly formed species may be left in a vibrationally excited state. Infrared photons can also vibrationally excite molecules directly. In both cases, collisional de-excitation can then heat the gas. Dust-gas heating In the ISM, gas and dust are not in thermodynamical equilibrium (they have different temperatures). If the dust is warmer than the gas, gas atoms bouncing off a grain can be an important gas heating source. If the gas is warmer, this process is really a cooling process.
15 Cosmic rays Cosmic rays: they are NOT rays! They are high-energy relativistic particles with energies of order of several hundred MeV whereas their energy density in Milky Way is estimated to be 1 ev/cm3. They were discovered in 1912 by V. Hess. Cosmic rays are in principle consisting of ~90% hydrogen nuclei (protons), ~9% helium nuclei, while the remaining ~1% corresponds to heavier nuclei than helium. Since cosmic rays carry charge, they follow the magnetic field lines of the entire Galaxy and are therefore bound to it. In general, every particle moving at such high energies can be considered as a cosmic ray particle. Victor F Hess in the balloon s basket sometime between 1911 and years later Hess won the Nobel Prize.
16 Cosmic-ray and X-ray heating Cosmic ray particles consist primarily of high-energy protons and electrons. Their origin is mainly due to supernova explosions, although other mechanisms also exist. Cosmic ray protons and X-rays can both ionize hydrogen atoms: (p,x) + HI (p', X') + HII + e Cosmic rays can penetrate a diffuse cloud and can contribute as a heating source well inside a dense area. A high-energy proton can ionize a gas atom. The substantial kinetic energy of the resulting primary electron can be lost through collisions with other electrons or through ionization or excitation of gas atoms or molecules. X-rays are so energetic that the primary electron created by X-ray absorption can be energetic enough to lead to secondary ionization.
17 Heating vs cooling The most dominant heating mechanism in diffuse clouds is the dust photoelectric heating. Cooling of the diffuse ISM gas is mainly due to Forbidden Line emission, particularly in low-lying states in neutral OI and especially in singly ionised carbon, CII. Very strong forbidden lines occur in the farinfrared: CII 158μm, OI 146μm. Putting in the dust grain heating rates and forbidden line cooling rates for typical diffuse ISM cloud densities of around n~100 cm -3, gives estimates of kinetic temperatures of ~ Kelvin.
18 Example of PDRs Density: n=1000 cm-3 Radiation field: χ=10χ0 (Draine) Chemical network of 33 species and 330 reactions
19 CI dominated CO dominated CII dominated H2 dominated HI dominated Example of PDRs
20 Benchmarking...
21 Example of PDRs
22 Example of PDRs
23 Heating functions
24 Cooling functions
25 Local emissivities
26 Radiative transfer If gas velocity is zero
27 Radiative transfer DO i=1,itot Calculate Tex, Bnu(Tex) ENDDO DO velocity = min, max DO i=1,itot Calculate optical depth at velocity ENDDO DO i=1,itot-1 (integration) Calculate Radiative Transfer ENDDO ENDDO Convert to units of brightness temperature and/or antenna temperature
28 Brightness temperature of CO
29 Optically thin vs Optically thick
30 Radiative transfer in 3D simulations
31 Radiative transfer in 3D simulations
The Birth Of Stars. How do stars form from the interstellar medium Where does star formation take place How do we induce star formation
Goals: The Birth Of Stars How do stars form from the interstellar medium Where does star formation take place How do we induce star formation Interstellar Medium Gas and dust between stars is the interstellar
More informationThe Interstellar Medium
The Interstellar Medium Fall 2014 Lecturer: Dr. Paul van der Werf Oortgebouw 565, ext 5883 pvdwerf@strw.leidenuniv.nl Assistant: Kirstin Doney Huygenslaboratorium 528 doney@strw.leidenuniv.nl Class Schedule
More informationMidterm Results. The Milky Way in the Infrared. The Milk Way from Above (artist conception) 3/2/10
Lecture 13 : The Interstellar Medium and Cosmic Recycling Midterm Results A2020 Prof. Tom Megeath The Milky Way in the Infrared View from the Earth: Edge On Infrared light penetrates the clouds and shows
More informationAstrophysics of Gaseous Nebulae and Active Galactic Nuclei
SECOND EDITION Astrophysics of Gaseous Nebulae and Active Galactic Nuclei Donald E. Osterbrock Lick Observatory, University of California, Santa Cruz Gary J. Ferland Department of Physics and Astronomy,
More informationChapter 10 The Interstellar Medium
Chapter 10 The Interstellar Medium Guidepost You have begun your study of the sun and other stars, but now it is time to study the thin gas and dust that drifts through space between the stars. This chapter
More informationAstrochemistry. Lecture 10, Primordial chemistry. Jorma Harju. Department of Physics. Friday, April 5, 2013, 12:15-13:45, Lecture room D117
Astrochemistry Lecture 10, Primordial chemistry Jorma Harju Department of Physics Friday, April 5, 2013, 12:15-13:45, Lecture room D117 The first atoms (1) SBBN (Standard Big Bang Nucleosynthesis): elements
More informationBeyond the Visible -- Exploring the Infrared Universe
Beyond the Visible -- Exploring the Infrared Universe Prof. T. Jarrett (UCT) Infrared Window Telescopes ISM -- Galaxies Infrared Window Near-infrared: 1 to 5 µm Mid-infrared: 5 to 50 µm
More informationLecture 18 - Photon Dominated Regions
Lecture 18 - Photon Dominated Regions 1. What is a PDR? 2. Physical and Chemical Concepts 3. Molecules in Diffuse Clouds 4. Galactic and Extragalactic PDRs References Tielens, Ch. 9 Hollenbach & Tielens,
More informationUniverse Now. 9. Interstellar matter and star clusters
Universe Now 9. Interstellar matter and star clusters About interstellar matter Interstellar space is not completely empty: gas (atoms + molecules) and small dust particles. Over 10% of the mass of the
More informationA World of Dust. Bare-Eye Nebula: Orion. Interstellar Medium
Interstellar Medium Physics 113 Goderya Chapter(s): 10 Learning Outcomes: A World of Dust The space between the stars is not completely empty, but filled with very dilute gas and dust, producing some of
More informationThermal Equilibrium in Nebulae 1. For an ionized nebula under steady conditions, heating and cooling processes that in
Thermal Equilibrium in Nebulae 1 For an ionized nebula under steady conditions, heating and cooling processes that in isolation would change the thermal energy content of the gas are in balance, such that
More informationLecture 9. Quasars, Active Galaxies and AGN
Lecture 9 Quasars, Active Galaxies and AGN Quasars look like stars but have huge redshifts. object with a spectrum much like a dim star highly red-shifted enormous recessional velocity huge distance (Hubble
More informationAtoms and Star Formation
Atoms and Star Formation What are the characteristics of an atom? Atoms have a nucleus of protons and neutrons about which electrons orbit. neutrons protons electrons 0 charge +1 charge 1 charge 1.67 x
More informationChapter 21 Galaxy Evolution. How do we observe the life histories of galaxies?
Chapter 21 Galaxy Evolution How do we observe the life histories of galaxies? Deep observations show us very distant galaxies as they were much earlier in time (old light from young galaxies). 1 Observing
More informationNumber of Stars: 100 billion (10 11 ) Mass : 5 x Solar masses. Size of Disk: 100,000 Light Years (30 kpc)
THE MILKY WAY GALAXY Type: Spiral galaxy composed of a highly flattened disk and a central elliptical bulge. The disk is about 100,000 light years (30kpc) in diameter. The term spiral arises from the external
More informationPhysics and Chemistry of the Interstellar Medium
Physics and Chemistry of the Interstellar Medium Sun Kwok The University of Hong Kong UNIVERSITY SCIENCE BOOKS Sausalito, California * Preface xi The Interstellar Medium.1.1 States of Matter in the ISM
More informationChapter 9. The Formation and Structure of Stars
Chapter 9 The Formation and Structure of Stars The Interstellar Medium (ISM) The space between the stars is not completely empty, but filled with very dilute gas and dust, producing some of the most beautiful
More informationChapter 16 Lecture. The Cosmic Perspective Seventh Edition. Star Birth Pearson Education, Inc.
Chapter 16 Lecture The Cosmic Perspective Seventh Edition Star Birth 2014 Pearson Education, Inc. Star Birth The dust and gas between the star in our galaxy is referred to as the Interstellar medium (ISM).
More informationPossible Extra Credit Option
Possible Extra Credit Option Attend an advanced seminar on Astrophysics or Astronomy held by the Physics and Astronomy department. There are seminars held every 2:00 pm, Thursday, Room 190, Physics & Astronomy
More informationGas 1: Molecular clouds
Gas 1: Molecular clouds > 4000 known with masses ~ 10 3 to 10 5 M T ~ 10 to 25 K (cold!); number density n > 10 9 gas particles m 3 Emission bands in IR, mm, radio regions from molecules comprising H,
More information6. Interstellar Medium. Emission nebulae are diffuse patches of emission surrounding hot O and
6-1 6. Interstellar Medium 6.1 Nebulae Emission nebulae are diffuse patches of emission surrounding hot O and early B-type stars. Gas is ionized and heated by radiation from the parent stars. In size,
More informationLecture 2: Introduction to stellar evolution and the interstellar medium. Stars and their evolution
Lecture 2: Introduction to stellar evolution and the interstellar medium Stars and their evolution The Hertzsprung-Russell (HR) Diagram (Color-Magnitude Diagram) Apparent and Absolute Magnitudes; Dust
More informationClicker Question: Clicker Question: What is the expected lifetime for a G2 star (one just like our Sun)?
How Long do Stars Live (as Main Sequence Stars)? A star on Main Sequence has fusion of H to He in its core. How fast depends on mass of H available and rate of fusion. Mass of H in core depends on mass
More informationStellar evolution Part I of III Star formation
Stellar evolution Part I of III Star formation The interstellar medium (ISM) The space between the stars is not completely empty, but filled with very dilute gas and dust, producing some of the most beautiful
More informationAstrochemistry the summary
Astrochemistry the summary Astro 736 Nienke van der Marel April 27th 2017 Astrochemistry When the first interstellar molecules were discovered, chemists were very surprised. Why? Conditions in space are
More informationPhysics Homework Set 2 Sp 2015
1) A large gas cloud in the interstellar medium that contains several type O and B stars would appear to us as 1) A) a reflection nebula. B) a dark patch against a bright background. C) a dark nebula.
More informationThe Ecology of Stars
The Ecology of Stars We have been considering stars as individuals; what they are doing and what will happen to them Now we want to look at their surroundings And their births 1 Interstellar Matter Space
More informationAccretion Disks. Review: Stellar Remnats. Lecture 12: Black Holes & the Milky Way A2020 Prof. Tom Megeath 2/25/10. Review: Creating Stellar Remnants
Lecture 12: Black Holes & the Milky Way A2020 Prof. Tom Megeath Review: Creating Stellar Remnants Binaries may be destroyed in white dwarf supernova Binaries be converted into black holes Review: Stellar
More informationChapter 11 The Formation of Stars
Chapter 11 The Formation of Stars A World of Dust The space between the stars is not completely empty, but filled with very dilute gas and dust, producing some of the most beautiful objects in the sky.
More informationChapter 11 Review. 1) Light from distant stars that must pass through dust arrives bluer than when it left its star. 1)
Chapter 11 Review TRUE/FALSE. Write 'T' if the statement is true and 'F' if the statement is false. 1) Light from distant stars that must pass through dust arrives bluer than when it left its star. 1)
More informationInterstellar Medium and Star Birth
Interstellar Medium and Star Birth Interstellar dust Lagoon nebula: dust + gas Interstellar Dust Extinction and scattering responsible for localized patches of darkness (dark clouds), as well as widespread
More informationComponents of Galaxies Gas The Importance of Gas
Components of Galaxies Gas The Importance of Gas Fuel for star formation (H 2 ) Tracer of galaxy kinematics/mass (HI) Tracer of dynamical history of interaction between galaxies (HI) The Two-Level Atom
More informationX Rays must be viewed from space used for detecting exotic objects such as neutron stars and black holes also observing the Sun.
6/25 How do we get information from the telescope? 1. Galileo drew pictures. 2. With the invention of photography, we began taking pictures of the view in the telescope. With telescopes that would rotate
More informationGalaxies with Active Nuclei. Active Galactic Nuclei Seyfert Galaxies Radio Galaxies Quasars Supermassive Black Holes
Galaxies with Active Nuclei Active Galactic Nuclei Seyfert Galaxies Radio Galaxies Quasars Supermassive Black Holes Active Galactic Nuclei About 20 25% of galaxies do not fit well into Hubble categories
More informationEnergy. mosquito lands on your arm = 1 erg. Firecracker = 5 x 10 9 ergs. 1 stick of dynamite = 2 x ergs. 1 ton of TNT = 4 x ergs
Energy mosquito lands on your arm = 1 erg Firecracker = 5 x 10 9 ergs 1 stick of dynamite = 2 x 10 13 ergs 1 ton of TNT = 4 x 10 16 ergs 1 atomic bomb = 1 x 10 21 ergs Magnitude 8 earthquake = 1 x 10 26
More informationThe Interstellar Medium (ch. 18)
The Interstellar Medium (ch. 18) The interstellar medium (ISM) is all the gas (and about 1% dust) that fills our Galaxy and others. It is the raw material from which stars form, and into which stars eject
More informationThe Milky Way Galaxy. Some thoughts. How big is it? What does it look like? How did it end up this way? What is it made up of?
Some thoughts The Milky Way Galaxy How big is it? What does it look like? How did it end up this way? What is it made up of? Does it change 2 3 4 5 This is not a constant zoom The Milky Way Almost everything
More informationAstronomy 10 Test #2 Practice Version
Given (a.k.a. `First ) Name(s): Family (a.k.a. `Last ) name: ON YOUR PARSCORE: `Bubble your name, your student I.D. number, and your multiple-choice answers. I will keep the Parscore forms. ON THIS TEST
More informationPhysics 224 The Interstellar Medium
Physics 224 The Interstellar Medium Lecture #11: Dust Composition, Photoelectric Heating, Neutral Gas Outline Part I: Dust Heating & Cooling continued Part III: Dust Emission & Photoelectric Heating Part
More informationINTRODUCTION TO SPACE
INTRODUCTION TO SPACE 25.3.2019 The Galaxy II: Stars: Classification and evolution Various types of stars Interstellar matter: dust, gas Dark matter ELEC-E4530 Radio astronomy: the Sun, pulsars, microquasars,
More informationPublished in: LOW-METALLICITY STAR FORMATION: FROM THE FIRST STARS TO DWARF GALAXIES
University of Groningen Interstellar Chemistry Spaans, Marco Published in: LOW-METALLICITY STAR FORMATION: FROM THE FIRST STARS TO DWARF GALAXIES DOI: 10.1017/S1743921308024885 IMPORTANT NOTE: You are
More informationThe Interstellar Medium. Papillon Nebula. Neutral Hydrogen Clouds. Interstellar Gas. The remaining 1% exists as interstellar grains or
The Interstellar Medium About 99% of the material between the stars is in the form of a gas The remaining 1% exists as interstellar grains or interstellar dust If all the interstellar gas were spread evenly,
More informationReview: Properties of a wave
Radiation travels as waves. Waves carry information and energy. Review: Properties of a wave wavelength (λ) crest amplitude (A) trough velocity (v) λ is a distance, so its units are m, cm, or mm, etc.
More informationAn Introduction to Galaxies and Cosmology
An Introduction to Galaxies and Cosmology 1.1 Introduction Milky Way (our galaxy - Galaxy) Fig. 1.1 A photograph of one hemisphere of the night sky. (D.di Cicco, Sky Publishing Corp.) 1011 stars 1012
More information18. Stellar Birth. Initiation of Star Formation. The Orion Nebula: A Close-Up View. Interstellar Gas & Dust in Our Galaxy
18. Stellar Birth Star observations & theories aid understanding Interstellar gas & dust in our galaxy Protostars form in cold, dark nebulae Protostars evolve into main-sequence stars Protostars both gain
More informationChapter One. Introduction
Chapter One Introduction The subject of this book is the most beautiful component of galaxies the gas and dust between the stars, or interstellar medium. The interstellar medium, or ISM, is, arguably,
More informationA Far-ultraviolet Fluorescent Molecular Hydrogen Emission Map of the Milky Way Galaxy
A Far-ultraviolet Fluorescent Molecular Hydrogen Emission Map of the Milky Way Galaxy (The Astrophysical Journal Supplement Series, 231:21 (16pp), 2017 August) November 14, 2017 Young-Soo Jo Young-Soo
More informationPhysics and chemistry of the interstellar medium. Lecturers: Simon Glover, Rowan Smith Tutor: Raquel Chicharro
Physics and chemistry of the interstellar medium Lecturers: Simon Glover, Rowan Smith Tutor: Raquel Chicharro This course consists of three components: Lectures Exercises Seminar [Wed., 2-4] [Thu., 4-5]
More informationProperties of Electromagnetic Radiation Chapter 5. What is light? What is a wave? Radiation carries information
Concepts: Properties of Electromagnetic Radiation Chapter 5 Electromagnetic waves Types of spectra Temperature Blackbody radiation Dual nature of radiation Atomic structure Interaction of light and matter
More informationChapter 19 Reading Quiz Clickers. The Cosmic Perspective Seventh Edition. Our Galaxy Pearson Education, Inc.
Reading Quiz Clickers The Cosmic Perspective Seventh Edition Our Galaxy 19.1 The Milky Way Revealed What does our galaxy look like? How do stars orbit in our galaxy? Where are globular clusters located
More informationThe Physics of the Interstellar Medium
The Physics of the Interstellar Medium Ulrike Heiter Contact: 471 5970 ulrike@astro.uu.se www.astro.uu.se Matter between stars Average distance between stars in solar neighbourhood: 1 pc = 3 x 1013 km,
More information8: Composition and Physical state of Interstellar Dust
8: Composition and Physical state of Interstellar Dust James Graham UC, Berkeley 1 Reading Tielens, Interstellar Medium, Ch. 5 Mathis, J. S. 1990, AARA, 28, 37 Draine, B. T., 2003, AARA, 41, 241 2 Nature
More informationInterstellar Medium by Eye
Interstellar Medium by Eye Nebula Latin for cloud = cloud of interstellar gas & dust Wide angle: Milky Way Summer Triangle (right) α&β Centauri, Coal Sack Southern Cross (below) Dust-Found in the Plane
More informationReminders! Observing Projects: Both due Monday. They will NOT be accepted late!!!
Reminders! Website: http://starsarestellar.blogspot.com/ Lectures 1-15 are available for download as study aids. Reading: You should have Chapters 1-14 read. Read Chapters 15-17 by the end of the week.
More informationLIFE CYCLE OF A STAR
LIFE CYCLE OF A STAR First stage = Protostar PROTOSTAR Cloud of gas and dust many light-years across Gravity tries to pull the materials together Eventually, at the center of the ball of dust and gas,
More informationThe Universe and Light
The Big Bang The big bang theory states that at one time, the entire universe was confined to a dense, hot, supermassive ball. Then, about 13.7 billion years ago, a violent explosion occurred, hurling
More informationAstrophysics of Gaseous Nebulae
Astrophysics of Gaseous Nebulae Astrophysics of Gaseous Nebulae Bright Nebulae of M33 Ken Crawford (Rancho Del Sol Observatory) Potsdam University Dr. Lidia Oskinova lida@astro.physik.uni-potsdam.de HST
More informationChapter 33 The History of a Star. Introduction. Radio telescopes allow us to look into the center of the galaxy. The milky way
Chapter 33 The History of a Star Introduction Did you read chapter 33 before coming to class? A. Yes B. No You can see about 10,000 stars with the naked eye. The milky way Radio telescopes allow us to
More informationPART 3 Galaxies. Gas, Stars and stellar motion in the Milky Way
PART 3 Galaxies Gas, Stars and stellar motion in the Milky Way The Interstellar Medium The Sombrero Galaxy Space is far from empty! Clouds of cold gas Clouds of dust In a galaxy, gravity pulls the dust
More informationCosmic Evolution, Part II. Heavy Elements to Molecules
Cosmic Evolution, Part II Heavy Elements to Molecules First a review of terminology: Element Atom Electro- magnetic Electrons Nucleus Electromagnetic Strong Nuclear Compound Molecule Protons Neutrons Neutral
More informationGalaxies and the Universe. Our Galaxy - The Milky Way The Interstellar Medium
Galaxies and the Universe Our Galaxy - The Milky Way The Interstellar Medium Our view of the Milky Way The Radio Sky COBE Image of our Galaxy The Milky Way Galaxy - The Galaxy By Visual Observation
More informationWarm Molecular Hydrogen at high redshift with JWST
Warm Molecular Hydrogen at high redshift with JWST Pierre Guillard Institut d Astrophysique de Paris Université Pierre et Marie Curie he Warm H 2 with JWST Outline and take-home messages 1. Observations
More informationScience 30 Unit C Review Outline GCCHS. Negatively charged Positively charged Coulomb Conductor Electric potential difference
Science 30 Unit C Review Outline GCCHS Negatively charged Positively charged Coulomb Conductor Electric potential difference volt voltage Insulator Test body Gravitational field Field lines Solar wind
More informationDark Matter ASTR 2120 Sarazin. Bullet Cluster of Galaxies - Dark Matter Lab
Dark Matter ASTR 2120 Sarazin Bullet Cluster of Galaxies - Dark Matter Lab Mergers: Test of Dark Matter vs. Modified Gravity Gas behind DM Galaxies DM = location of gravity Gas = location of most baryons
More informationAstro-2: History of the Universe
Astro-2: History of the Universe Lecture 13; May 30 2013 Previously on astro-2 Energy and mass are equivalent through Einstein s equation and can be converted into each other (pair production and annihilations)
More informationPhysics HW Set 3 Spring 2015
1) If the Sun were replaced by a one solar mass black hole 1) A) life here would be unchanged. B) we would still orbit it in a period of one year. C) all terrestrial planets would fall in immediately.
More informationThe Sun. The Sun is a star: a shining ball of gas powered by nuclear fusion. Mass of Sun = 2 x g = 330,000 M Earth = 1 M Sun
The Sun The Sun is a star: a shining ball of gas powered by nuclear fusion. Mass of Sun = 2 x 10 33 g = 330,000 M Earth = 1 M Sun Radius of Sun = 7 x 10 5 km = 109 R Earth = 1 R Sun Luminosity of Sun =
More informationTaking fingerprints of stars, galaxies, and interstellar gas clouds
- - Taking fingerprints of stars, galaxies, and interstellar gas clouds Absorption and emission from atoms, ions, and molecules Periodic Table of Elements The universe is mostly hydrogen H and helium He
More informationPhotoionization Modelling of H II Region for Oxygen Ions
Journal of Materials Science and Chemical Engineering, 2015, 3, 7-16 Published Online April 2015 in SciRes. http://www.scirp.org/journal/msce http://dx.doi.org/10.4236/msce.2015.34002 Photoionization Modelling
More informationChapter 16 Lecture. The Cosmic Perspective Seventh Edition. Star Birth Pearson Education, Inc.
Chapter 16 Lecture The Cosmic Perspective Seventh Edition Star Birth Star Birth 16.1 Stellar Nurseries Our goals for learning: Where do stars form? Why do stars form? Where do stars form? Star-Forming
More informationGiant Star-Forming Regions
University of Heidelberg, Center for Astronomy Dimitrios A. Gouliermis & Ralf S. Klessen Lecture #1 Introduction & Overview Introduction to HII Regions In this Lecture Motivation for this Course Schedule
More informationCOSMIC RAYS DAY INTRODUCTION TO COSMIC RAYS WINDWARD COMMUNITY COLLEGE - SEPTEMBER 26, 2015 VERONICA BINDI - UNIVERSITY OH HAWAII
COSMIC RAYS DAY WINDWARD COMMUNITY COLLEGE - SEPTEMBER 26, 2015 VERONICA BINDI - UNIVERSITY OH HAWAII INTRODUCTION TO COSMIC RAYS MAJOR QUESTIONS: Are there forms of matter in the Universe that do not
More informationChapter 11 The Formation and Structure of Stars
Chapter 11 The Formation and Structure of Stars Guidepost The last chapter introduced you to the gas and dust between the stars that are raw material for new stars. Here you will begin putting together
More informationChapter 5 Light and Matter
Chapter 5 Light and Matter Stars and galaxies are too far for us to send a spacecraft or to visit (in our lifetimes). All we can receive from them is light But there is much we can learn (composition,
More informationEffects of Massive Stars
Effects of Massive Stars Classical HII Regions Ultracompact HII Regions Stahler Palla: Sections 15.1, 15. HII Regions The salient characteristic of any massive star is its extreme energy output, much of
More informationChapter 19 Lecture. The Cosmic Perspective. Seventh Edition. Our Galaxy Pearson Education, Inc.
Chapter 19 Lecture The Cosmic Perspective Seventh Edition Our Galaxy 19.1 The Milky Way Revealed Our goals for learning: Where are we located within our galaxy? What does our galaxy look like? How do stars
More informationNOTES: 5.3 Light and Atomic Spectra (more Quantum Mechanics!)
NOTES: 5.3 Light and Atomic Spectra (more Quantum Mechanics!) Light WAVE or PARTICLE? Electromagnetic Radiation Electromagnetic radiation includes: -radio waves -microwaves -infrared waves -visible light
More informationStar-Forming Clouds. Stars form in dark clouds of dusty gas in interstellar space. The gas between the stars is called the interstellar medium.
Star Birth Chapter 16 Lecture 16.1 Stellar Nurseries The Cosmic Perspective Our goals for learning: Where do stars form? Why do stars form? Seventh Edition Star Birth Where do stars form? Star-Forming
More informationAstr 2320 Thurs. April 27, 2017 Today s Topics. Chapter 21: Active Galaxies and Quasars
Astr 2320 Thurs. April 27, 2017 Today s Topics Chapter 21: Active Galaxies and Quasars Emission Mechanisms Synchrotron Radiation Starburst Galaxies Active Galactic Nuclei Seyfert Galaxies BL Lac Galaxies
More informationChapter 12: The Lives of Stars. How do we know it s there? Three Kinds of Nebulae 11/7/11. 1) Emission Nebulae 2) Reflection Nebulae 3) Dark Nebulae
11/7/11 Chapter 12: The Lives of Stars Space is Not Empty The Constellation Orion The Orion Nebula This material between the stars is called the Interstellar Medium It is very diffuse and thin. In fact
More informationEnergy Source for Active Galactic Nuclei
Quasars Quasars are small, extremely luminous, extremely distant galactic nuclei Bright radio sources Name comes from Quasi-Stellar Radio Source, as they appeared to be stars! Can have clouds of gas near
More informationStars, Galaxies & the Universe Lecture Outline
Stars, Galaxies & the Universe Lecture Outline A galaxy is a collection of 100 billion stars! Our Milky Way Galaxy (1)Components - HII regions, Dust Nebulae, Atomic Gas (2) Shape & Size (3) Rotation of
More informationAn Introduction to Radio Astronomy
An Introduction to Radio Astronomy Bernard F. Burke Massachusetts Institute of Technology and Francis Graham-Smith Jodrell Bank, University of Manchester CAMBRIDGE UNIVERSITY PRESS Contents Preface Acknowledgements
More information3/1/18 LETTER. Instructors: Jim Cordes & Shami Chatterjee. Reading: as indicated in Syllabus on web
Astro 2299 The Search for Life in the Universe Lecture 9 Last time: Star formation Formation of protostars and planetary systems This time A few things about the epoch of reionization and free fall times
More informationInterstellar Astrophysics Summary notes: Part 2
Interstellar Astrophysics Summary notes: Part 2 Dr. Paul M. Woods The main reference source for this section of the course is Chapter 5 in the Dyson and Williams (The Physics of the Interstellar Medium)
More informationThe 158 Micron [C II] Line: A Measure of Global Star Formation Activity in Galaxies Stacey et al. (1991) ApJ, 373, 423
The 158 Micron [C II] Line: A Measure of Global Star Formation Activity in Galaxies Stacey et al. (1991) ApJ, 373, 423 Presented by Shannon Guiles Astronomy 671 April 24, 2006 Image:[C II] map of the galaxy
More informationSome HI is in reasonably well defined clouds. Motions inside the cloud, and motion of the cloud will broaden and shift the observed lines!
Some HI is in reasonably well defined clouds. Motions inside the cloud, and motion of the cloud will broaden and shift the observed lines Idealized 21cm spectra Example observed 21cm spectra HI densities
More informationAstr 2310 Thurs. March 23, 2017 Today s Topics
Astr 2310 Thurs. March 23, 2017 Today s Topics Chapter 16: The Interstellar Medium and Star Formation Interstellar Dust and Dark Nebulae Interstellar Dust Dark Nebulae Interstellar Reddening Interstellar
More informationA100 Exploring the Universe: The Milky Way as a Galaxy. Martin D. Weinberg UMass Astronomy
A100 Exploring the Universe: The Milky Way as a Galaxy Martin D. Weinberg UMass Astronomy astron100-mdw@courses.umass.edu November 12, 2014 Read: Chap 19 11/12/14 slide 1 Exam #2 Returned and posted tomorrow
More informationAstronomy 104: Second Exam
Astronomy 104: Second Exam Stephen Lepp October 29, 2014 Each question is worth 2 points. Write your name on this exam and on the scantron. Short Answer A The Sun is powered by converting hydrogen to what?
More informationChapter 19 Lecture. The Cosmic Perspective Seventh Edition. Our Galaxy Pearson Education, Inc.
Chapter 19 Lecture The Cosmic Perspective Seventh Edition Our Galaxy Our Galaxy 19.1 The Milky Way Revealed Our goals for learning: Where are we located within our galaxy? What does our galaxy look like?
More informationChapter 15 The Milky Way Galaxy
Chapter 15 The Milky Way Galaxy Guidepost This chapter plays three parts in our cosmic drama. First, it introduces the concept of a galaxy. Second, it discusses our home, the Milky Way Galaxy, a natural
More informationChapter 16: Star Birth
Chapter 16 Lecture Chapter 16: Star Birth Star Birth 16.1 Stellar Nurseries Our goals for learning: Where do stars form? Why do stars form? Where do stars form? Star-Forming Clouds Stars form in dark clouds
More informationNeutron Stars. Neutron Stars and Black Holes. The Crab Pulsar. Discovery of Pulsars. The Crab Pulsar. Light curves of the Crab Pulsar.
Chapter 11: Neutron Stars and Black Holes A supernova explosion of an M > 8 M sun star blows away its outer layers. Neutron Stars The central core will collapse into a compact object of ~ a few M sun.
More informationModel of Hydrogen Deficient Nebulae in H II Regions at High Temperature
Journal of Materials Science and Chemical Engineering, 2015, 3, 21-29 Published Online August 2015 in SciRes. http://www.scirp.org/journal/msce http://dx.doi.org/10.4236/msce.2015.38004 Model of Hydrogen
More informationCosmic Rays. M. Swartz. Tuesday, August 2, 2011
Cosmic Rays M. Swartz 1 History Cosmic rays were discovered in 1912 by Victor Hess: he discovered that a charged electroscope discharged more rapidly as he flew higher in a balloon hypothesized they were
More information5) What spectral type of star that is still around formed longest ago? 5) A) F B) A C) M D) K E) O
HW2 Name MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) The polarization of light passing though the dust grains shows that: 1) A) the dust grains
More informationChapter 15 The Milky Way Galaxy. The Milky Way
Chapter 15 The Milky Way Galaxy The Milky Way Almost everything we see in the night sky belongs to the Milky Way We see most of the Milky Way as a faint band of light across the sky From the outside, our
More informationAstr 5465 March 6, 2018 Abundances in Late-type Galaxies Spectra of HII Regions Offer a High-Precision Means for Measuring Abundance (of Gas)
Astr 5465 March 6, 2018 Abundances in Late-type Galaxies Spectra of HII Regions Offer a High-Precision Means for Measuring Abundance (of Gas) Emission lines arise from permitted (recombination) and forbidden
More informationDust. The four letter word in astrophysics. Interstellar Emission
Dust The four letter word in astrophysics Interstellar Emission Why Dust Dust attenuates and scatters UV/optical/NIR Amount of attenuation and spectral shape depends on dust properties (grain size/type)
More information