Astronomy

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Author:
krhill94
ID:
59042
Filename:
Astronomy
Updated:
2011-01-10 20:50:21
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Astronomy
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Astronomy CH1
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  1. Andromeda Galaxy (M31; the Great Galaxy in Andromeda)
    The nearest spiral galaxy to the Milky Way.
  2. asteroid
    • A relatively small and rocky object that orbits a star;
    • asteroids are officially considered part of a category known as "small solat system bodies."
  3. astronomical unit (AU)
    The average distance (semimajor axis) of Earth from the Sun, which is about 150 million km.
  4. axis tilt (of a planer in our solar system)
    The amount by which a planet's axis is tilted with respect to a line perpendicular to the ecliptic plane.
  5. Big Bang
    The name given to the event thought to mark the birth of the universe.
  6. cluster of galaxies
    A collection of a few dozen or more galaxies bound together by gravity; smaller collections of galaxies are simply called groups.
  7. comet
    A relatively small, icy object that orbits a star. Like asteroids, comets are officially considered part of a category known as "small solat system bodies."
  8. cosmos
    An alternative name for the universe.
  9. dwarf planet
    An object that orbits the Sun and is massive enough for its gravity to have made it nearly round in shape, but for that does not qualify as an official planet because it has not cleared its orbital neighborhood. The dwarf planets of our solat system include the asteroid Ceres and the Kuiper belt objects Pluto, Eris, Haumea, and Makemake.
  10. ecliptic
    The Sun's apparent annual pathe among the constellations.
  11. ecliptic plane
    The plane of Earth's orbit around the Sun.
  12. expansion (of the universe)
    The idea that the space between galaxies or clusters of galaxies is growing with time.
  13. galaxy
    A huge collection of anywhere from a few hundred million to more than a trillion stars, all bound together by gravity.
  14. galaxy cluster
    A collection of a few dozen or more galaxies bound together by gravity; smaller collections of galaxies are simply called groups.
  15. geocentric universe (ancient belief in)
    The idea that Earth is the center of the entire universe.
  16. gravitationally bound system
    Any system of objects, such as a star system or a galxy, that is held together by gravity.
  17. group (of galaxies)
    A few to a few dozen galaxies bound together by gravity.
  18. Large Magellanic Cloud
    One of two small, irregular galaxies (the other is the Small Magellanic Cloud) located about 150,000 lightyears away; it probably orbits the Milky Way Galaxy.
  19. Light-yeat (ly)
    The distance that light can travel in 1 year, which is 9.46 trillion km.
  20. Local Group
    The group of about 40 galaxies to which the Milky Way Galaxy belongs.
  21. local solar neighborhood
    The portion of the Milky Way Galaxy that is located relatively close (within a few hundred to a couple thousand light-years) to our Sun.
  22. Local Supercluster
    The supercluster of galaxies to which the Local Group belongs.
  23. Milky Way
    Used both as the name of our galaxy and to refer to the band of light we see in the sky when we look into the plane of the Milky Way Galaxy.
  24. minor planets
    An alternative name for asteroids.
  25. moon
    An object that orbits a planet.
  26. nuclear fusion
    The process in which two (or more) smaller nuclei slam together and make one larger nucleus.
  27. observable universe
    The portion of the entire universe that, at least in principle, can be seen from earth.
  28. orbit
    The path followed by a celestial body because of gravity; an orbit may be bound ( elliptical) or unbound (parabolic or hyperbolic),
  29. planet
    A moderately large object that orbits a star and shines primarily by reflecting light from its star. More precisely, according to a definition approved in 2006, a planet is an object that (1) orbits a star (but itself neither a star nor a moon); (2) is massive enough for its own gravity to give it a nearly round shape; and (3) has cleared the neighborhood around its orbit. Objects that meet the first two criteria but not the third, including Ceres, Pluto, and Eris, are designated dwarf planets.
  30. revolution
    The orbital motion of one object around another.
  31. rotation
    The spinning of an object around its axis.
  32. satellite
    Any object orbiting another object.
  33. Small Magellanic Cloud
    • One of two small, irregular
    • galaxies (the other is the Large Magellanic Cloud) located about 150,000 light-years away; it probably orbits the Milky Way Galaxy.
  34. small solar system body
    An asteroid, comet, or other object that orbits a star but is too small to qualify as a planet or dwarf planet.
  35. solar system (or star system)
    A star (sometimes more than one star) and all the objects that orbit it.
  36. star
    A large, glowing ball of gas that generates energy through nuclear fusion in its core. The term star is sometimes applied to objects that are in the process of becoming true stars (e.g., protostars) and to the remains of stars that have died (e.g., neutron stars).
  37. star system
    A star (some times more than one star) and all the objects that orbit it.
  38. superclusters
    The largest known structures in the universe, consisting of many clusters of galaxies, groups of galaxies, and individual galaxies.
  39. synchrotron radiation
    A type of radio emission that occurs when electrons moving at nearly the speed of light spiral around magnetic field lines.
  40. universe
    The sum total of all matter and energy.

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