Solar System Review

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Across
  1. 3. A rocky inner planet with a solid surface, such as Mercury, Venus, Earth, and Mars.
  2. 5. The Sun and all the celestial objects bound to it by gravity, including planets, moons, asteroids, and comets.
  3. 9. A planet composed of elements heavier than hydrogen and helium, like Uranus and Neptune.
  4. 11. The spinning of a celestial body on its axis.
  5. 12. The universe cooled enough for electrons and protons to combine and form neutral atoms, allowing light to travel freely.
  6. 14. The earliest moment in the universe’s history, lasting less than a trillionth of a second after the Big Bang.
  7. 17. The star at the center of our solar system that provides energy to Earth.
  8. 18. An infinitely dense and hot point from which the universe is thought to have originated.
  9. 19. A massive, luminous sphere of plasma that generates energy through nuclear fusion.
  10. 21. A cooler, darker region on the Sun's surface caused by magnetic activity.
  11. 22. The scientific explanation of the origin of the universe, stating it began as a singularity around 13.8 billion years ago and has been expanding ever since.
Down
  1. 1. The substance that makes up physical objects in the universe, including ordinary (baryonic) matter and dark matter.
  2. 2. The formation of the first atomic nuclei (hydrogen, helium, and trace amounts of lithium) shortly after the Big Bang.
  3. 4. An icy celestial body that releases gas and dust, forming two glowing tails when it approaches the Sun.
  4. 6. The movement of a celestial body around another body in space.
  5. 7. An instrument used to observe distant objects, including galaxies and the CMB.
  6. 8. The force of attraction between two objects with mass.
  7. 10. A stream of charged particles released from the Sun’s outer atmosphere.
  8. 13. The ongoing process of the universe growing in size over time.
  9. 15. A rocky body smaller than a planet, that orbits the Sun, mostly found in the asteroid belt between Mars and Jupiter.
  10. 16. A celestial body that orbits a star, is spherical in shape, and has cleared its orbit of other debris.
  11. 20. The curved path of an object around a star, planet, or moon.
  12. 23. A large planet made mostly of hydrogen and helium, such as Jupiter and Saturn.