Stars Crossword

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Across
  1. 1. The characteristic way in which the intensity of radiation emitted by a hot object depends on frequency. The frequency at which the emitted intensity is highest is an indication of the temperature of the radiating object.
  2. 4. The very largest of the large, hot, bright stars at the uppermost, left end of the main sequence on the Hertzsprung-Russell diagram.
  3. 5. Fragments of collapsing gas and dust that did not contain enough mass to initiate core nuclear fusion. Such an object is then frozen somewhere along its pre-main-sequence contraction phase, continually cooling into a compact dark object. Because of their small size and low temperature, these are extremely difficult to detect observationally.
  4. 7. A star that suddenly increases in brightness, often by a factor of as much as 10,000 then slowly fades back to its original luminosity. These are the result of an explosion on the surface of a white-dwarf star, caused by matter falling onto its surface from the atmosphere of a binary companion.
  5. 8. Objects that emit radiation in the form of rapid pulses with a characteristic pulse period and duration. Charged particles, accelerated by the magnetic field of a rapidly rotating neutron star, flow along the magnetic field lines, producing radiation that beams outward as the star spins on its axis.
  6. 11. Bright lines in a specific location of the spectrum of radiating material, corresponding to emission of light at a certain frequency. A heated gas in a glass container produces these in its spectrum.
  7. 12. Explosive death of a star, caused by the sudden onset of nuclear burning (Type 1), or an enormously energetic shock wave (Type 2).
  8. 14. The brightness of a star as it appears from Earth, expressed using the magnitude scale.
  9. 16. One of the basic properties used to characterize stars, it is defined as the total energy radiated by a star each second, at all wavelengths.
  10. 17. A plot of luminosity against temperature (or spectral class) for a group of stars.
  11. 18. An imaginary spherical surface surrounding a collapsing star, with radius equal to the Schwarzschild radius, within which no event can be seen, heard, or known about by an outside observer.
Down
  1. 1. Stars found on the main sequence of the Hertzsprung-Russell diagram, but which should already have evolved off the main sequence, given its location on the diagram. These are thought to have formed from mergers of lower mass stars.
  2. 2. A dense ball of neutrons that remains at the core of a star after a supernova explosion has destroyed the rest of the star. These are typically about 20 km across, and contain more mass than the Sun.
  3. 3. Two stars orbiting around each other.
  4. 6. The apparent magnitude a star would have if it were placed at a standard distance of 10 parsecs from Earth, expressed using the magnitude scale.
  5. 9. Dark lines in an otherwise continuous bright spectrum, where light within one narrow frequency range has been removed.
  6. 10. A region of space where the pull of gravity is so great that nothing, not even light, can escape. A possible outcome of the evolution of a very massive star.
  7. 13. A giant star whose surface temperature is relatively low so that it glows red.
  8. 15. A small star with sufficiently high temperature that it glows white. These are the end product of low to mid-mass stars at the end of their lives.