vocab

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Across
  1. 3. The surface at which the escape velocity of a collapsing star is equal to the speed of light.
  2. 5. A large assemblage of stars without radial symmetry.
  3. 9. The classification of stars according to their temperatures using the characteristics of their spectra.
  4. 12. A large assemblage of stars, gas, dust, and dark matter orbiting a common center.
  5. 13. A plot of luminosity against surface temperature or spectral type for a group of stars.
  6. 15. A star that experiences a sudden outburst of radiant energy, temporarily exponentially increasing its luminosity.
  7. 18. A measure of the observed light received from a star or other object.
  8. 21. A low-mass star that has exhausted most or all of its nuclear fuel and has collapsed to a very small size.
  9. 22. molecular clouds Large, cold, interstellar clouds with large diameters where massive stars form.
  10. 23. An assemblage of stars, oval in shape, that contains no conspicuous interstellar material.
  11. 24. A cloud of interstellar gas or dust.
  12. 25. Middle-age stars that can be found running diagonally through the middle of an HR diagram.
  13. 27. A morphological classification scheme for galaxies. Often described as a tuning fork, after the shape of the diagram created from it.
  14. 28. A spherical collection of stars that orbits a galactic core as a satellite.
  15. 32. The rate at which an object must travel in order to break free of the influence of gravity.
  16. 33. The central part of a galaxy.
  17. 34. A star of large luminosity and radius.
  18. 35. A collapsed, massive body whose escape velocity is equal to or greater than the speed of light.
Down
  1. 1. The outermost extent of a galaxy with a sparse distribution of stars.
  2. 2. The distance from the center of a black hole to its event horizon.
  3. 4. A theoretical point of zero volume and infinite density to which any black hole must collapse.
  4. 6. A variable radio source of small angular size that emits very rapid radio pulses in very regular periods.
  5. 7. An object of very high redshift that looks like a star but is extragalactic and highly luminous.
  6. 8. A flattened, rotating, large assemblage of stars with pinwheel-like arms of interstellar material and stars winding out from its nucleus.
  7. 10. The upper boundary to the mass of a white dwarf.
  8. 11. An object, midway in size between a planet and a star, with a mass about 1/100 that of the sun.
  9. 14. A measure of the luminosity of an object like a star.
  10. 16. An explosion that marks the final stage of stellar evolution.
  11. 17. The apparent displacement of a nearby star caused by the revolution of the Earth around the sun.
  12. 19. One of the 107 galaxies, nebulas, star clusters, and other deep sky objects classified with an M followed by a number.
  13. 20. Stars that pulsate radially, varying in both temperature and diameter, to produce brightness changes with a well-defined stable period and amplitude.
  14. 26. A star of extremely high density composed almost entirely of neutrally charged subatomic particles.
  15. 29. A star of very high luminosity and relatively low temperature.
  16. 30. Two stars that revolve around each other.
  17. 31. The main portion of a galaxy. Consists of a nucleus, bulge, and spiral arms.