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  1. Sun's mass
    2 X 1030kg
  2. Sun's size
    radius= 700,000 km
  3. Sun's surface temperature
    6,000 K
  4. Sun's luminosity
    3.8 X 1026 Watts
  5. Sun's lifetime
    10 trillion yrs
  6. The Sun's Inner Layers
    • Convection zone: energy generated in the solar core travel up, transported by the rising of hot gas and falling of cool gas
    • Radiation zone: 1/3 way to center; energy moves outward primarily in the form of photons of light
    • Core: source of sun's energy; nuclear fusion transforming hydrogen into helium
  7. Fusion in the sun
    • the high temperature and pressure allow for fusion of hydrogen into helium
    • The proton proton chain: 2 protons fuse and release a positron and neutrino(occurs twice in reaction)->1p 1n; this fuses to a proton(occurs 2X)->2p 1n; these two nuclei fuse and release 2 protons->2p 2n
  8. Gravitational Equilibrium
    • a state of balance in which the force of gravity pulling inward is precisely counteracted by pressure pushing out
    • ex) acrobat stack
  9. What are the directly measurable qualities of stars?
    • color
    • apparent brightness
    • those close enough, distance via parallax
  10. Apparent magnitudes
    • describes a stars apparent brightness
    • *a larger apparent mag means a dimmer apparent brightness
  11. Absolute Magnitudes
    • describes a stars luminosity
    • 1 mag = 2.512
  12. Luminosity
    • the total amount of pwr a star emits into space at all wavelength's
    • direct means= color, brightness, distance
  13. Brightness
    • how bright the stars look in our sky
    • need to know luminosity and distance
  14. Parallax
    • used to find distaces for "near" stars
    • a star's distance= precise amount fo the star's annual shift due to parallax
    • looking at an object from two different directionsImage Upload 1
  15. Binary Stars
    • Sys. in which 2 stars continually orbit one another
    • To find mass, need orbital period and the seperation of the 2 stars
    • Visual Binary: both stars can be resolved through a telescope (observe orbit to find orbital period)
    • Eclipsing Binary: 2 stars happen to be orbitting in the plane of ourline of sight, so that each star will periodically eclipse the other(measure time btwn eclipses to measure orbital period)
    • Spectroscopic Binary: who binary nature is revealed b/c we detect the spectral lines of one or both stars alternately (measure time it takes the spectral lines to switch back and forth to find orbital period)
  16. Stars Classification
    • O: dark blue, > 30,000K
    • B: blue, 30,000-10,000K
    • A: white, 10,000-7,500
    • F: dull white, 7,500-6,000K
    • G: yellowish, 6,000-5,000K
    • K: orange, 5,000-3,500K
    • M: red, <3,500K
    • The spectral type consists of a letter and a #
  17. Luminosity classes
    • ^ I- supergiants
    • | II- bright giants
    • | III- giants
    • | IV- subgiants
    • | V- main-sequence stars
  18. H-R Diagram
    • A Hertzsprung-Russell Diagram
    • Def: a graph plotting individual stars as points, with stellar luminosity on the vertical axis and surface temp on the horizontal
    • Image Upload 2
  19. Star Clusters
    • 1) all the stars in a cluster lie at about the same distance from earth
    • 2) all stars in a cluster formed at the same time
    • Open Clusters: several thousand stars; found in the disks of galaxies and contain young stars; don't last long
    • Globular Clusters: million+ stars; found in halos of galaxies(milky way halo); center is packed tight; contain very old stars
  20. Significance of Mass
    • mass governs ALL the star's characteristics
    • ex) temp, luminosity, lifetime
  21. What do stars form from?
    Stars form by the gravitational collapse of dense clumps of interstellar dust, gas, and molecules
  22. How do stars form?
    • inward pull of gravity vs. outward push of pressure(thermal pressure)
    • Stars form in molecular cloudsdue to high temps and low densities which gives gravity the upper hand
    • when the core starts trapping thermal energy released by gravitational contraction
    • pressure begins to push back, contraction slows down and the central part of the cloud becomes a protostar.
    • Matter from surrounding cloud build up mass of protostar
  23. Where do stars form?
    • they form in the disk of galaxies
    • usually form in open clusters
  24. Smallest and largest mass possible for stars
    • Lowest: .08Msun; anyhting less is called a brown dwarf
    • Highest: >150Msun
    • more low mass stars that high mass stars
  25. Can stars change their mass?
    • Normally, stars can't change mass but can in a binary star sys
    • Mass Exchange: A star begins to swell at the end of it's Hydrogen burning life and transfers mass to it's companion
  26. How do stars change during their main sequence lifetime?
    slowly, their luminosity increases
  27. Life of a low mass star
    • most of its life, it fuses H->HE via the proton-proton chain
    • When H is exhausted, the core begins to shrick while the star itself expands and becomes a red giant
    • the HE core becomes hot enough->helium flash that initiates HE fusion
    • this causes HE->C = end of life
    • core shrinks again
    • outer layers expand->thermal pulses and expels outer shell
    • the remaining stellar core is a white dwarf
    • (have a long life)
  28. Life as a high mass star
    • Fuse H->HE via the CNO cycle(cycle of reactions)
    • exhaust H core->H shell burning
    • ->several stages->burning successively heavier elements
    • increase rate of fusion->swell and become a supergiant
    • they die during a supernova, scattering newly produced elements
    • a supernova occurs when iron is formed in the core->core collapses and explodes=supernova remnant
    • leave a neutron star ot a blackhole
  29. What are the three basic stellar corpses?
    • White dwarf: from a low mass star; if it exceed 1.4Msun, it will explode like a bomb as a white dwarf supernova- due to H acquired through accretion disk
    • Neutron Stars: from high mass star; pulsars(rapid pulses of radiation as it rotates) provided the first direct proof for the existance of neutron stars
Card Set
review for the third exam
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