ASTR Midterm 2

  1. Cassini divide:
    • 1. largest division between some of the rings
    • 2. space caused by gravity of moon mimas
  2. Roche limit
    1. minimum radius at which a satellite may orbit without being broken apart by tidal forces
  3. Uranus characteristics
    • 1.small angual size
    • 2. 4 times the diameter of earth
    • 3. no core
    • 4. methane in atmosphere makes planet blueish-green
    • 5. 10 thin rings,
    • 6.retrograde motion bc of its obliquity
    • 7. orbital period of 84 yrs
    • 8. voyager 2
    • 9. shepard moon
    • 10. somewhat larger denisty than uranus
  4. Triton
    Neptune's largest moon; only major moon to revolve around a planet in a retrograde direction

    Will crash onto Neptune in future
  5. who was pluto discovered by
    clyde tombaugh in 1930
  6. what was used to discover pluto
    blink comparator
  7. pluto
    • 1. 17 degree tilt to ecliptic
    • 2. methane atmosphere
    • 3.moon-- Charon
    • 4. pluto 1/5 our moon
    • 5. small and ecentric orbit: thus maybe a former moon of Neptune
  8. Piazzi
    Discorvered asteroids in 1801
  9. asteroids
    • known as minor planets
    • ceres is the largest asteroid
    • Pallsa and Vesta have diameters greater than 300 km
  10. asteroid belt
    asteroids that orbit the sun at distanc eof 2.2-3.3 aU
  11. apollo asteroids
    50 asteroids with diameters lager than 1 km tat have eccentric orbits that cross the Earth's orbit
  12. Kirkwood Gap
    gaps between asteroids in asteroid belt; due to synchronous tugs from Jupiter on the asteroids which used to be located there
  13. trojan asteroids
    two groups of asteroids which are located at Jupiter's distance from the Sun
  14. The orgin of the asteroids
    Asteroids are primordial material that never formed into a planet because of Jupiter's gravitational influence
  15. Edmund Halley
    • Used Newton's methods to calculate orbits of many coments
    • corrently predicted next return of what would become Comet Halley
  16. Parts of a comet
    • 1. Head: consists of coma and nucleus
    • 2. coma: part of comet's head made up of a diffuse cloud of gas and dust
    • 3. Nucleus: comet is solid chunk of a comet, locatd in the head
    • 4.tail: gas and/or dust that is swept away from comet's head.
  17. Ion tail v. Dust tail
    • 1. Ion tail: is a straight tail
    • 2. dust tail: curved tail
  18. what is the nucleus of a comet like
    a dirty snowball (water, ice, frozen carbon dioxide, and small grains
  19. how comet "dies"
    gradual evaporation of their nuclei

    trhough evaporationof all volatile material

    falling into the sun
  20. Jan Oort and the Oort cloud
    jan: proposed comet cloud exists in a spherical shell

    these billion of comet nuclei exist in Oort cloud
  21. Kuiper belt
    band of comets and dwarf planets that exists closer to the solar system than the oort cloud
  22. scattered disk
    third source of commets (beside kuiper belt, oort cloud) iwhich is larger than Kuiper belt and smaller than Oort cloud
  23. three different meteroid sizes
    • 1. smallest meteoroids slowed down at top of Earth's atmoshpere---> micro meteorites
    • 2. streak in sky from dust grain sized meteroid is heated up by passage through earth's atmoshpere--> meteor
    • very brigh meteorr--> fireballs
    • 3. Largest meteoroids: able to pass through Earth's atmosphere

    meteorite: meteroid after it passes through atmosphere
  24. radiant
    point in the sky from which the meteors of a shower appear to radiate
  25. three categories of meteorites
    1. irons: iron meteorites that are made up of 80%-90% (with some nickel)

    2. Stones: stony meteorites that can contain flakes of iron and nickel

    3. Stony irons: meteorites that are half stone and half iron
  26. Sun characteristics
    • 1. is a G2 star, that is the main sequence phase of its life
    • 2. in 5 billion yrs will become red giant star
    • 3. has differential rotation like outer planets
    • 4.
  27. solar constant energy striking earth at the rate of 1,380 watts
  28. solar luminosity
    total rate at which sun releases energy into space in all directions
  29. solar limb
    edge of solar disk
  30. limb darkening
    how solar disks look dimmer near their edges,

    proof that the temperature decreases with increasing height within the sun's photosphere
  31. granulation
    divison of the sun's surface into small convection cells
  32. granules
    areas where hot material is rising from below and then descending
  33. what is the chemical make up of the photosphere
    • 78% hydrogen
    • 20% helium
  34. sun's core
    must hold more helium than the photosphere since some of hydrogen that was there has already been converted into helium during lif eof the sun
  35. chromosphere
    region of the solar atmoshpere 2,000-3,000 km thick

    lies between photosphere and corona
  36. transition zone
    directly above the chromophere, 200 km thick,
  37. spicules
    narrow jets of gas which are part of the chromosphere but exted through the transition zone into the corona
  38. solar corona
    portion of the solar atmoshpere only visible during a total solar eclipse

    above the transition zone
  39. How is the chromosphere heated?
    1. shockwaves: produced in solar interior and dump their energy in the corona

    2. magnetic reconnection heating: changes in coronal magnetic field
  40. coronal holes
    large dark area in the corona

    are cooler than the surrounding corona
  41. solar wind
    continous flow of nuclei and electrons from the sun
  42. thomas harriott
    first person after Galileo to report sunspots
  43. sunspots
    1500 degrees coller than surrounding photosphere

    locations where sun's magnetic field passes from its interior through the photosphere into the atmoshpere
  44. Zeeman effect
    measures the sun's magnetic field, by splitting spectral lines by a strong magnetic field
  45. solar maximum and minimum
    maximum: tie when most sunsposets are visjible on solar surface
Card Set
ASTR Midterm 2
Chapter 21-24