Stars and Cosmology

  1. Chromatic Aberrations
    • Deviation of light rays by lenses which causes the images to be blurred.
    • - Caused by lenses only.
    • - Causes colors making up the light to focus on different planes so you can see the separate colors.
    • - Fixed by adding another lens.
  2. Atmospheric Aberrations
    • The apparent displacement of a celestial body due to the finite speed of light and the motion of the observer with the earth
    • - Gets worse with larger telescopes that allow you to look at objects more closely
    • - Use adaptive optics to correct
  3. Adaptive Optics
    • - a mechanism by which astronomical images are corrected for effects of turbulence in the atmosphere
    • - Eliminates turbulence
    • - Can't go over 300x mag without this
    • - Use a central computer to manage an artificial star test to correct image
  4. ReFRActor Telescope
    • LENS is the main light gatherer
    • - Bends light
    • - Acts like a prism
  5. ReFLEctor Telescope
    Employs a MIRROR as the main light gatherer
  6. Newtonian Telescope
    • - Eyepiece up at top
    • - Light hits CONCAVE mirror first
    • - Small optical flat mirror to refocus light and bounce through eyepiece
  7. Cassegrain Telescope (Classical and Ritchey-Chretien)
    • - CONVEX mirror used to bounce light back through eyepiece
    • - Only difference from Newtonian is mirror used
    • - Prefer compact nature of scope. Folds in on self
  8. Catadioptric Telescope
    • -Uses lens AND mirror as main light gatherer
    • - Similar to telephoto lenses
  9. Binoculars
    • - Twin refracting telescopes
    • - Makes it so you can see a wider area
    • - Use the same system for telescopes. Putting them in pairs to get better resolution
  10. German Equatorial Telescope Mount
    • - One motor moves it
    • - Can't hold very much weight
  11. Alt- azimuth Telescope Mount
    • - How they track the stars
    • - More common now
    • - Word- class telescopes use this kind
    • - Holds more weight
  12. Very Large Array Telescopes (VLAs)
    • - Link telescopes together to work as one
    • - Began with radio telescopes
    • - Makes telescopes work as if they were miles in diameter
  13. Major Planet
    • - Must be large enough to be round
    • - Must have "cleaned out" orbit
    • - Center of mass must be contained within boundary of planet
    • (moon) o-----O (earth)
    • here--------->^
  14. "Cleaned out" orbit
    • Planet gets so big that it pulls everything into it.
    • No debris or anything are left floating around it
  15. Terrestrial Planets in our system...
    • Mercury (closest to sun)
    • Venus
    • Earth
    • Mars
  16. Terrestrial Planet
    • - Solid surface
    • - High comparative density (to gascous planets)
    • - Small by comparison and a NiFe core
  17. Jovian Planets
    • - Comparatively large
    • - Low density
    • - Small FeNi core
    • - Predominately Hydrogen and Helium (similar makeup as stars.)
    • - Lie in outer part of OUR solar system (probably not normal for universe)
  18. Jovian planets in our system...
    • - Jupiter (closest to sun)
    • - Saturn
    • - Uranus
    • - Neptune (furthest from sun)
  19. Minor (Dwarf) Planets
    • Lacked one or more major criteria so are deemed dwarfs instead.
    • - all in our system are big enough to be round but some are not round
    • - originally thought to be broken up planets
  20. Minor planets in our system....
    • - Ceres (largest)
    • - Pluto (poor guy was demoted)
    • - Eris
  21. Moons
    • - Orbit major or minor planets
    • - Can be captured by the planet
  22. Asteroid Belt
    • - Thousands of celestial bodies, probably down to pebble sized
    • - Orbits between Mars and Jupiter
    • - Not considered a destroyed planet
    • - Asteroids are held in Jupiter's orbit
    • - Ceres is the largest
  23. Trans Neptunian Objects
    • - Anything in our solar system that orbits outside the orbit of Neptune
    • - Came about when Pluto was demoted
  24. Kuiper Belt Objects (KBOs)
    • - Orbits in a donut shape at 50 AU around the sun
    • - About 20 known and named
    • - Likely 1000s or millions
  25. Comets
    • A relatively small extraterrestrial body consisting of a frozen mass that travels around the sun in a highly elliptical orbit
    • - Short period comets <200 years
    • - Long period comets > 200 years
  26. Oort Cloud
    • Spherical leftovers at 50,000 AU in all directions.
    • - None have been discovered so far but there is strong evidence that they exist
  27. Meteor ("Shooting Star")
    • A rock from space that is falling to Earth through our atmosphere
    • - Don't usually hit
    • - Leftovers from the forming of the solar system
    • - Usually very small. Ionize while falling and then disintegrate
  28. Meteorite
    • Meteor (rock) that has landed on Earth
    • - Earth gains and estimated 2 tons a year from these
    • - 3 different kinds
  29. Irons (Siderites)
    • Type of meteorite that looks just like aluminum.
    • It is highly magnetic.
  30. Stones (Aerolites)
    meteorite that is consists mostly of stony matter
  31. Stony-Irons (Siderolites)
    Highly prized because they have glass in them
  32. Accretion disk
    • An accretion disc is a structure formed by diffuse material in orbital motion around a central body.
    • The central body is typically a young star, a protostar, a white dwarf, a neutron star, or a black hole.
    • Gravity causes material in the disc to spiral inward towards the central body
    • It is made of a relatively cold gas
    • Phase 2 of the Solar Nebula Hypothesis
  33. Protosun
    • A dense condensation of material that is still in the process of accreting matter to form a star.
    • Phase 3 of the Solar Nebula Hypothesis
  34. T Tauri (cocoon stage)
    • The young star will produce strong winds in the T-Tauri stage, named after the prototype star in the constellation Taurus.
    • These strong winds eject much of the surrounding cocoon gas and dust.
    • With most of the cocoon gas blown away, the forming star itself becomes visible to the outside for the first time.
    • Stage 4 of the Solar Nebula Hypothesis
  35. Main Sequence
    • When star gains enough heat that converting H into He begins.
    • Begin Nuclear fusion
    • Star spends most of it's life in main sequence
    • Stage 5 of Solar Nebula Hypothesis
  36. Planetissimal
    • One of a class of bodies that are theorized to have formed the planets after condensing from diffuse matter early in the history of the solar system
    • Formed from leftovers in the accretion disk
    • Only about 1 km or so in diameter
  37. Protoplanets
    • The collection of matter, in the process of condensation, from which a planet is formed.
    • Form from planetissimals. Further on in the process of forming a planet
    • About 1000km to 2000km in diameter
    • Becomes rount at 400km
  38. Chemical Differentiation
    • The separation of planetary material according to density
    • Ices and silicates float to the top
    • Heavier elements sink to core which becomes molten
  39. Disk Instability Model
    • Old thinking of how our solar system formed
    • Suggest ices settled directly into Jovian planets
  40. Binary Star System
    • A system in which there is enough left over from the solar nebula that a 2nd star forms
    • Believed that our sun formed in a binary system
  41. Exoplanets
    • An extrasolar planet that orbits a star other than earth's sun
    • Almost all planets close to parent star
    • All hot Jupiter's are within Mercury's distance to their parent star
  42. Dopler Shift
    • How much a star shifts from a massive planet
    • - 1st (easiest) way of discovering exoplanets
    • - Determine the period of the stellar shift the mass and distance is known
    • - Works well when there is only one planet
    • - if you have it's period, then you have it's temp, then you have it's color, and know it's mass
  43. Transit
    • Two things appear to intersect from our point of view
    • Star will fade when a larger planet transits it
    • 2nd (harder) way of discovering exoplanets
    • Works only if plane of our solar system matches same plane of exoplanet
  44. Disk Instability Model
    • Jovian planets formed closer to sun
    • - Had near misses with other planets and got thrown out farther from sun because of gravity
    • - Possible explanation why our solar system is different that others
  45. Radioactive age-dating
    • How rocks are dated
    • - dated from when they were last molten
    • - how we know age of solar system---date meteors, etc.
  46. Photosphere
    • The solar "surface"
    • We can see about 400 km into it
    • It is opaque because it has an extra negative electron, otherwise we'd see a lot further into the sun
  47. Limb Darkening
    • refers to the diminishing of intensity in the image of a star as one moves from the center of the image to the edge or "limb" of the image.
    • occurs as the result of two effects:
    • The density of the star diminishes as the distance from the center increases
    • The temperature of the star diminishes as the distance from the center increases.
  48. Granulation
    • Result of the rising and falling of hot gas that takes place in the convective zone in the photosphere of the sun
    • Can be 1000s of miles in diameter
    • 300k cooler than center parts
  49. Chromosphere
    • Middle layer of sun seen only during a total solar eclipse
    • Much thinner than our atmosphere
  50. Spicules
    • Very bright spikes that extend from the Sun into the chromosphere.
    • Only last about 15 minutes
  51. Corona
    • Outer layer of the sun that extends 1 million km
    • One millionth as bright as the photosphere
    • Looks like a halo around the sun---not visible to naked human eye
  52. Solar wind
    • Energy that escapes from the sun
    • Composed of electrons from H and He with trace amounts of other elements
    • The sun ejects over a million tons per day--pretty insignificant amount to sun
  53. Sun Spots
    • Cooler, darker areas that can't penetrate a solar filter
    • Extremely magnetic (this increases with size)
    • Consists of Umbra and Penumbra
    • Obeys the Stefan-Boltzman law----They are .3 or 30% as bright or lum. as photosphere
  54. Umbra
    • Darker coolest center of sun spots
    • Red according to Wein's law
  55. Penumbra
    • borders the umbra of sun spots
    • intermediate in temperature
    • Can be splotchy or filamentary in structure
    • Orange according to Wein's law
  56. Stephan Boltzman Law
    The total energy radiated from a blackbody is proportional to the fourth power of the temperature of the body. Also known as fourth-power law; Stefan's law of radiation
  57. Sunspot (solar) Cycles
    • Sunspot counts rise and fall on an 11 year cycle
    • 22 years is a total cycle meaning the polarity goes from positive, to negative and back to positive
    • Caused by differential rotation
  58. Zeeman Effect
    • relating to sunspot (solar) cycles
    • High magnetism will split absorption line into three instead of one
  59. Prominences
    • Cooler, bright red columns of plasma seen against the dar "sky" off the limb of the sun
    • Rise up from magnetic sun spots
    • Sometimes they can connect to other spots if they get strong enough and form loops
    • Seen on the side of the sun
  60. Filaments
    • Same as prominences only seen on the front of the sun--against the brighter photosphere
    • They appear darker because they are cooler
  61. Solar Flares (CMEs)
    • CME-Coronal Mass Ejection
    • Super large prominences
    • Can loop to connect two sun spots but they are huge
  62. Plage
    a bright region in the chromosphere of the Sun, typically found in regions of the chromosphere near sunspots
  63. Kelvin-Helmholtz Contraction
    • As gases are compressed, the temp will rise.
    • Works initially, but not in the long run
  64. Hydrostatic Equilibrium
    • Pressure of gravity balances with released energy
    • Balance of gravity created by its mass and outward release of its gas pressure
    • The sun is in Main sequence when it has achieved this
  65. Thermal Equilibrium
    • Thermal reactions in the core of the sun must be transported to the surface.
    • Too little release and the sun will heat up
    • Too much release and the sun will cool down
  66. Radiative Diffusion
    • Another method of transportation of energy in sun
    • Occurs in the inner 25% of the sun
    • This is the same 25% where nuclear fusion is occurring
    • Energy radiates out like a radiator
  67. Convection
    • One method of transportation of energy in sun
    • Vertical swirling, cooler gases sink while heated gases rise
    • Occurs in the outer 30% of the sun
    • We can see this happening
  68. How does time effect transportation in the sun?
    • The core is dense so photons move slowly
    • Once to the surface they travel away at the speed of light
  69. What is the temperature of the sun?
    5800 Kelvin
  70. Neutrinos
    • Subatomic byproducts of nuclear fusion
    • Theorized for a long time but not able to be detected
    • Finally detected after 40 yrs
    • This is how we know there is nuclear fusion going on
  71. Stellar parallax
    • The apparent change in the position of a nearby star when observed from Earth due to our planet's yearly orbit around the Sun.
    • This method allows astronomers to calculate distances to stars that are less than 100 parsecs from Earth.
    • Formula is d=1/p
    • Further away, less accurate
  72. Luminosity
    • One way of measuring the distance of stars
    • Uses the inverse square law (double the distance, luminosity is 4 times less)
    • Luminosity is known by color or spectral class, both give it's temperature
  73. Magnitude Scale
    • Based on a number system developed by Hipparchus, a Greek philosopher in BC times
    • The smaller the number, the brighter the object
    • The bigger the number, the fainter the object
    • Each whole number =2.512 x brighter/dimmer than previous whole number
    • Unaided human eye can't see past magnitude 6
  74. Apparent Magnitude
    • The brightness of a star as it appears from earth using the magnitude scale
    • Designated with a "m" (small case)
  75. Absolute Magnitude
    • The apparent magnitude of any star if it were placed at 10pc from Earth using the magnitude scale
    • Designated with a "M" (upper case)
  76. Mnemonic for Star Temperatures
    Oh be a fine girl, kiss me like that!
Card Set
Stars and Cosmology
Flashcards for basic Stars and Cosmo physics class