Joy of Science Experience the evolution of the Universe, Earth and Life

Transcription

1 Joy of Science Experience the evolution of the Universe, Earth and Life Review of last class Introduction to Astronomy Contents of today s lecture Quiz time

2 Review Review 1 n Science is a way of producing A. absolutely certain solutions to problems B. ultimate truth C. final answers to questions D. non of the above

3 Review Review 1 n Science is a way of producing A. absolutely certain solutions to problems B. ultimate truth C. final answers to questions D. non of the above Science is a way of thinking. Science is a way of gathering information. Science is a way of explaining all aspects of the universe.

4 Review Review 2 n Which of the following procedures are included in the scientific method A. careful observations B. tentative guesses C. analysis of data D. all of the above

5 Review Review 2 n Which of the following procedures are included in the scientific method A. careful observations B. tentative guesses C. analysis of data D. all of the above

6 Review Review 2 n Which of the following procedures are included in the scientific method A. careful observations B. tentative guesses C. analysis of data D. all of the above A tentative guess is a hypothesis.

7 Review Review 3: Scientific Method Initial New experiment Observation and analysis of data Final Hypothesis supported Hypothesis not supported New Hypothesis stated

8 Review Review 3: Scientific Method Initial Observation and analysis of data Final Hypothesis supported stated New experiment Hypothesis not supported n New Hypothesis What is the correct order of words that should be filled in the blanks? A. Observation -> Hypothesis -> Theory -> Law B. Hypothesis -> Observation -> Experiment -> Theory C. Experiment -> observation -> Hypothesis -> Theory D. Observation -> Experiment -> Hypothesis -> Theory E. Observation -> Experiment -> Hypothesis -> Law F. Observation -> Hypothesis -> Experiment -> Theory

9 Review Review 3: Scientific Method Initial Observation Hypothesis Experiment Observation and analysis of data Final Hypothesis supported Theory stated New experiment Hypothesis not supported n New Hypothesis What is the correct order of words that should be filled in the blanks? A. Observation -> Hypothesis -> Theory -> Law B. Hypothesis -> Observation -> Experiment -> Theory C. Experiment -> observation -> Hypothesis -> Theory D. Observation -> Experiment -> Hypothesis -> Theory E. Observation -> Experiment -> Hypothesis -> Law F. Observation -> Hypothesis -> Experiment -> Theory

10 Review Review 4 n Choose all which are non-scientific studies but claiming they are science. 1. ESP 3. astrology 2. astronomy 4. palmistry A. 1 B. 2,3 C. 3,4 D. 1,2,3 E. 1,2,4 F. 1,3,4 G. 1, 2, 3, 4

11 Review Review 4 n Choose all which are non-scientific studies but claiming they are science. 1. ESP 3. astrology 2. astronomy 4. palmistry A. 1 B. 2,3 C. 3,4 D. 1,2,3 E. 1,2,4 F. 1,3,4 G. 1, 2, 3, 4

12 Review Review 4 n Choose all which are non-scientific studies but claiming they are science. 1. ESP 3. astrology 2. astronomy 4. palmistry A. 1 B. 2,3 C. 3,4 D. 1,2,3 This type of studies are classified as E. 1,2,4 Pseudoscience. F. 1,3,4 G. 1, 2, 3, 4

13 Survey n Do you prefer no-class on May 6 for Golden-Week vacation? ( If your answer is Yes, you need to choose another day to make up for the missing class on May 6 ) A. Yes (vacation on May 6) B. No (class on May 6) C. Either is fine

14 Introduction Astronomy - Experience the evolution of the Stars Today s Keywords Astronomy, Star, Telescope, Fusion

15 Assignment #1: The Stars Biology Physics Chemistry Technology Great Idea Environment Astronomy Health and Safety Geology

16 Contents Outline of today s lecture 0. Introduction definitions, telescopes 1. The Sun 2. The Birth of stars 3. The Life of stars 4. The Death of stars

17 Introduction Astronomy n Astronomy: Study of objects in the heavens. Much about the nature and origins of stars have been discovered. n Star: Every star radiates energy so that we can see the star in the form of photons through telescopes and satellites as well as bare eyes. The Sun, the nearest star to Earth, is one of stars. n Measuring stars with telescopes and satellites: Primary source of data that provides mass, composition, history of the stars and their future behaviors too. n Measuring photons characters from stars (star s energy => Electromagnetic(EM) radiation => Photons) 1. wavelength 2. intensity 3. direction 4. variation of 1,2,3 with time

18 Introduction Photon spectrum n Photons have waves n All photon waves lie between gamma rays (shortest wave length à highest energy) and radio waves (longest wave length à smallest energy) n In visible light range: red (lower energy) > violet (higher energy) n Frequency è denotes energy

19 EM spectrum = photon spectrum Introduction n Picture

20 Telescopes Earth based Telescopes n Telescope: Device that focus and concentrate radiation from distant object (Radiation: radio wave, microwave, visible light, ) n Earth-based telescopes: - Optical telescope: Light strikes a mirror then focused on a detector such as eyes or electric detector - Radio telescope: Radio waves strikes a curved metal dish that focuses the waves on an antenna. Computer amplify and process signals.

21 Telescopes Earth based telescopes n pictures

22 Telescopes Orbiting Observatories - Satellite n Except for visible light and radio waves, all other EM radiations such as ultraviolet, infrared or X-rays are observed before they can reach the Surface of the Earth. => Need space-based telescopes! - Hubble Space Telescope (HST) - Chandra X-ray Observatory - Fermi Gamma Ray Telescope - Planck Observatory

23 Telescopes Satellite n Picture Hubble telescope

24 Reference: Hertzsprung-Russel Diagram n H-R Diagram: fates of stars in star s temperature vs. its energy n fig Main Sequence

25 The Sun The Sun The giver of life on our Earth and knowledge about stars Structure of the Sun: an example of main-sequence stars n The center - core - 10 % of the Sun s total volume - Energy generated through collisions of high energy particles by nuclear reactions (fusion) n Convection Zone - Energy transferred from the core to the surface by convection (turbulent) n Photosphere - A thin outer: the only part actually we can see, because it emits most of the light we see - Gaseous layers: Chromosphere, Corona

26 The Sun The Sun picture of sun structure 1. Core 2. Radiative zone 3. Convection Zone 4. Photosphere zone 5. Chromosphere 6. Corona 7. Sunspot

27 Reference: solar planets n Planet: celestial body orbiting a star n Mercury n Venus n Earth n Mars n Jupiter n Saturn n Uranus n Neptune n (Pluto)

28 The Sun Nuclear Fusion Reaction in the Sun n Sun s energy source: nuclear fusion reaction using hydrogen n Hydrogen: most common material in the universe and primary element of stars n Hydrogen burning: Three step fusion process to produce energy in the Sun s core (P: proton from hydrogen, D: deuterium with 1 proton and 1 neutron) Step 1: P +P à D + positron + neutrino + energy Step 2: D + D à Helium-3 + photon + energy Step 3: Helium-3 + Helium-3 à Helium proton + energy 4 hydrogen protons à 1 helium-4 + extra particles + energy è Hydrogen mass is converted to Energy

29 Reference n Fusion: process by which two or more atomic nuclei join together n Atom: nucleus (protons+ neutrons) + electrons n Nucleus (pl. nuclei): a dense core of atom, with protons and neutrons n Electron: subatomic particles carrying negative electric charge n Proton: subatomic particle carrying +1 electric charge n Neutron: subatomic particle with no charge n Hydrogen: smallest element with 1 proton no neutron n D (deuterium): stable isotope of hydrogen, with 1 proton 1 neutron n Positron: antiparticle of electron with positive charge

30 Reference: periodic table of elements n Atom: smallest component of an element having chemical properties of the element, consisting nucleus containing combinations of neutrons and protons and one or more electrons bound to the nucleus by electrical attraction; the number of protons determines the identity of the element. n a

31 Birth of Stars all starts from Birth hydrogen burning stage Stars live and die like everything else! The birth of stars n All stars are born in clouds of gases and other debris (Nebulae) n Nebulae typically contain 99% of hydrogen and helium n A nebula collapses onto itself slowly due to gravity, and the collapse causes to spin faster and faster (Imagine a kitchen sink as gravity and water in the sink as a gaseous cloud nebula ) n The fast rotation makes the outer flat and the center dense n As more and more mass pours into the center the pressure and temperature increase higher and higher à Nuclear fusion starts! è The birth of a star!!!

32 Hertzsprung-Russel Diagram n Hertzsprung-Russell Diagram: fates of stars in star s temperature vs. its energy n fig Main Sequence

33 Life Life of Stars different fates of stars n Stars about the mass of the Sun - Life as a continual battle against gravity - original cloud contracts due to gravity à particles collide and nuclear fusion stars to burn hydrogen à increase in temperature raises pressure à higher outward pressure balance the inward pull of gravity n Stars much less massive than the Sun - hydrogen burning is slow è faint Brown dwarf n Very large stars - more than 10 times as massive as the Sun - gravity is high enough so that helium burns to carbon, and then carbon undergoes fusion reaction to produce oxygen, magnesium, silicon and other larger nuclei until iron, the most stable element

34 Death Death of Stars n Stars about the mass of the Sun Sun: - When hydrogen is consumed up, gravity will begin to take over à begin to contract again à helium ( ash of hydrogen burning) starts to undergo nuclear fusion reaction so called Helium Burning, such as, He-4 + He-4 + He-4 à Carbon-12 + energy - increased energy by sudden collapse and then helium burning balloon out the surface of the star è Red Giant - as carbon accumulates in the core, a collapse will start slowly and stops at a stage è White Dwarf age 4.5 billion yrs, lifetime 11 billion yrs, Sun at red giant extends up to orbit of Venus, size of Sun at white dwarf is size of Earth (but thousands of times more massive)

35 Death Death of stars n Stars much less massive than Sun - nuclear fusion process is slow à continue to glow steadily for a hundred billion years without significant change in size, temperature, energy output (cf. Age of universe: 13.6 billion yrs) n Very large stars - pressure by gravity is large enough to combine electrons with protons in iron nuclei in the core è forming Neutrons à catastrophic collapse begins when all electrons disappear to form neutrons à pressure of neutrons balance balance gravity è rebounding à intense shock waves are set up when collapsing envelope of gas meets rebounding core of neutrons è Supernova

36 After supernova & Black Hole Neutron star, Pulsar and Black Hole n After Supernova Neutron stars - core of neutrons after a star explodes - typical neutron star might be about 16 km - hard to detect Pulsars - some neutron stars have strong magnetic field and rapid rotation - emit radio radiation signals à detected by radio telescope as a form of pulses n Largest stars Black holes - last step of largest stars (perhaps more than 50 times of Sun) - ultimate triumph of gravity à nothing, even light, can escape