Astrobiology: Understanding the Universe, Stars, and Galaxies - Chapter 3 - Prof. Harold G, Study notes of School management&administration

Download Astrobiology: Understanding the Universe, Stars, and Galaxies - Chapter 3 - Prof. Harold G and more Study notes School management&administration in PDF only on Docsity! The Universal Context of Life (Chap 3 – Bennett & Shostak) 1 February 2007 - Lecture 4 6 February 2007 – Lecture 5 HNRS 228 - Astrobiology Prof. Geller Overview of Chapter 3 The Universe and Life (3.1) Age, Size, Elements, Laws The Structure, Scale, and History of the Universe (3.2) Planets, Solar System, Galaxy, Local Group, Supercluster, Universe Big Bang Theory of creation of universe ⌧Evidence for expansion, age and composition The Nature of the Worlds (3.3) The solar system and its formation (remember 227) The Following Slides are from HONORS 227 1st Law of Thermodynamics In an isolated system, the total amount of energy, including heat energy, is conserved. ENERGY IS CONSERVED 2nd Law of Thermodynamics Two key components heat flows from a warmer body to a cooler body entropy increases remains constant or increases in time Wien’s Law Peak wavelength is inversely proportional to the temperature of the blackbody Intensity Frequency Cooler Body Hotter Body Peak Wavelength Stefan-Boltzmann Law Energy radiated by blackbody is proportional to the temperature to the 4th power •E = σ T4 Energy vs. Temperature 0 10000 20000 30000 40000 50000 60000 0 2 4 6 8 10 12 14 16 Temperature En er gy Doppler Shift A change in measured frequency caused by the motion of the observer or the source classical example of pitch of train coming towards you and moving away wrt light it is either red-shifted (away) or blue-shifted (towards) How Bright is It? Apparent Magnitude (from Earth) Absolute Magnitude How Hot Is It? >Remember Wien’s Law 0.01 4 0.001 4 0.0001 | 0.00001 100 1000 10000 Wavelength (nm) Classes for Spectra O,B,A,F,G,K,M There are also subclasses 0…9 Galaxies Elliptical Galaxies S0 (lenticular) Galaxies Spiral Galaxies Barred-Spiral Galaxies Irregular Galaxies The Big Bang Dark Energy Accelerated Expansion Afterglow Light ee Led ee ees ct Galaxies, Planets, etc. Inflation aE atte about 400 million yrs. Big Bang Expansion 13.7 billion years The Big Bang Summary Timescale Era Epochs Main Event Time after bang The Vacuum Era Planck Epoch Inflationary Epoch Quantum fluctuation Inflation <10-43 sec. <10-10 sec. The Radiation Era Electroweak Epoch Strong Epoch Decoupling Formation of leptons, bosons, hydrogen, helium and deuterium 10-10 sec. 10-4 sec. 1 sec. - 1 month The Matter Era Galaxy Epoch Stellar Epoch Galaxy formation Stellar birth 1-2 billion years 2-15 billion years The Degenerate Dark Era Dead Star Epoch Black Hole Epoch Death of stars Black holes engulf? 20-100 billion yrs. 100 billion - ???? What CMB means? Remember Wien’s Law Remember Doppler COBE results Putting it into context Taking the perspective of the universe with you at the center The CMB remainder... Using COBE DIRBE data for examining the fine differences fine structure of the universe ⌧led to the galaxies and their location Question for Thought Which stars have the longest life span? The lowest mass stars have the longest life span. Red dwarfs can live 100 billion years. Stars like our Sun live about 10 billion years. Question for Thought What is the Hertzsprung-Russell diagram? What is its significance and how can it be used? Basically a plot of temperature vs. luminosity. You can determine the approximate age of a star cluster with an H-R Diagram. You can follow the life cycle of a star with an H-R Diagram. Question for Thought Describe, in general, the life cycle of a star with a mass similar to our Sun. Gas cloud , Fragmentation, Protostar, Kelvin-Helmholz Contraction, Hayashi Track, Ignition, Adjustment to Main Sequence, Hydrogen Core Depletion, Hydrogen Shell Burning ("Red Giant Branch"), Helium Flash, Helium Core Burning/Hydrogen Shell Burning ("Helium MS" "Horizontal Branch"), Helium Core Depletion, Helium Shell Burning, Asymptotic Giant Branch, Planetary Nebula, White Dwarf Question for Thought What is a supernova? The catastrophic explosion of a star. It can be a star that is part of a binary star system or a standalone star. In the case of a standalone star, it is a star that is so massive that it goes through all of the fusion steps possible up to iron. Supernovae explosions result in the formation of either a neutron star or black hole. Question for Thought Describe the forces that keep a star in a state of hydrostatic equilibrium. Fusion generates energy that pushes out from the center of a star. Also gas pressure maintains a push out from the center. The weight of the star (gravity) keeps pulling the stellar material to the center of its mass. Question for Thought What is the source of the chemical elements of the universe? Hydrogen, helium and little lithium and berylium were made in the big bang formation of the universe. All other chemical elements up to Uranium (#92) were formed in stars. Elements up to iron are formed in stars during their life cycle. Elements beyond iron are born in supernovae explosions. The Following should help with the story of the formation of the Solar System Questions to Consider How did the solar system evolve? What are the observational underpinnings? Why are some elements (like gold) quite rare, while others (like carbon) are more common? Are there other solar systems? What evidence is there for other solar systems? (to be discussed later in semester) Observations to be Explained Each radioactive nucleus decays at its own characteristic rate, known as its half-life, which can be measured in the laboratory. This is key to radioactive age dating, which is used to determine the ages of rocks. The oldest rocks found anywhere in the solar system are meteorites, the bits of meteoroids that survive passing through the Earth’s atmosphere and land on our planet’s surface. Radioactive age-dating of meteorites, reveals that they are all nearly the same age, about 4.56 billion years old Radioactive dating of solar system rocks Earth ~ 4 billion years Moon ~4.5 billion years Log Plot of Abundance Logarithmic Plot of Chemical Abundance of Elements 1 10 100 1000 10000 100000 H He C N O Ne Mg Si Si Fe Chemical Species R el at iv e A bu nd an ce Another Log View Chemical Abundance vs. Atomic Number (Logarithmic Plot) 1 10 100 1000 10000 100000 0 5 10 15 20 25 30 Atomic Number R el at iv e A bu nd an ce A Linear View of Abundance Linear Plot of Chemical Abundance 0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 H He C N O Ne Mg Si Si Fe Chemical Species R el at iv e ab un da nc e Other Planet Observations Terrestrial planets are closer to sun Mercury Venus Earth Mars Jovian planets furthest from sun Jupiter Saturn Uranus Neptune Some Conclusions Planets formed at same time as sun Planetary and satellite/ring systems are similar to remnants of dusty disks such as that seen about stars being born (e.g. T Tauri stars) Planet composition dependent upon where it formed in solar system Nebular Condensation Physics Energy absorbed per unit area from sun = energy emitted as thermal radiator Solar Flux = Lum (Sun) / 4 x distance2 Flux emitted = constant x T4 [Stefan-Boltzmann] Concluding from above yields T = constant / distance0.5 A Pictorial View Gas pressure attempting to expand the cloud Nebula Gravitational force attempt ng to collapse the clou ’. CT] The cloud spins more rapidly as it collapses because of conservation of angular momentum Pictorial View Continued Side View e+ eS Side View: protosun HST Pictorial Evidence?