Universe

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Across
  1. 1. Way Galaxy The spiral galaxy that contains our solar system.
  2. 5. Diagram A graph that plots stars by brightness (luminosity) versus surface temperature.
  3. 7. background radiation Faint microwave radiation left over from the early universe after the Big Bang.
  4. 9. nebula An expanding shell of gas ejected by a dying medium-mass star.
  5. 10. A huge system of stars, gas, dust, and dark matter bound together by gravity.
  6. 11. A luminous ball of gas producing energy by nuclear fusion.
  7. 12. star A very large, luminous star much bigger than the Sun.
  8. 15. galaxy A galaxy with a flat disk and winding spiral arms where new stars often form.
  9. 16. matter Matter that does not emit light but exerts gravity, detected by its effects on galaxies.
  10. 19. Bang Theory The scientific theory that the universe began from a hot, dense state and has been expanding.
  11. 21. A collapsing dense region of gas and dust that will become a star before fusion begins.
  12. 23. All space, time, matter, and energy that exist.
  13. 24. galaxy A rounded or oval-shaped galaxy made mostly of older stars with little dust.
Down
  1. 1. sequence star A star in the stable, hydrogen-fusing stage of its life cycle.
  2. 2. Shift The change in wavelength or frequency of waves caused by relative motion between source and observer.
  3. 3. The curved path an object follows as it moves around another body due to gravity.
  4. 4. A cloud of gas and dust in space where stars can form.
  5. 6. year The distance that light travels in one year (about 9.46 trillion kilometers).
  6. 8. A cataclysmic explosion marking the death of a massive star.
  7. 13. galaxy A galaxy that lacks a regular shape or structure.
  8. 14. hole A region of space with gravity so strong that not even light can escape.
  9. 17. dwarf A small, dense stellar remnant left after a low- or medium-mass star sheds its outer layers.
  10. 18. energy A mysterious form of energy that causes the universe’s expansion to accelerate.
  11. 20. The force that pulls objects with mass toward each other.
  12. 22. system A star and all the objects gravitationally bound to it, such as planets and moons.