The Universe

2. A collection of galaxies that are gravitationally bound together.
4. A hypothetical form of matter that does not emit, absorb, or reflect light, but is thought to make up the majority of matter in the universe.
5. The scientific model explaining the origin of the universe, stating that it began with a massive explosion.
8. The entire universe, including all matter and energy.
12. A large collection of stars, gas, and dust held together by gravity.
13. A natural satellite that orbits a planet.
14. The portion of the universe that is beyond our ability to detect, either because it is too far away or because it is hidden by other objects or phenomena.
17. An explosion of a star that occurs when it runs out of fuel and collapses in on itself, releasing a massive amount of energy.
18. The path that an object follows as it revolves around another object in space.
19. A massive, luminous sphere of plasma held together by gravity, which produces energy through nuclear fusion.
20. The portion of the universe that we can detect and study, limited by the speed of light and the age of the universe.

1. A star and all the objects that orbit it, including planets, moons, asteroids, and comets.
3. The force that attracts two objects with mass towards each other.
6. A rocky object orbiting the sun, often found in the asteroid belt between Mars and Jupiter.
7. An object that orbits a planet or other celestial body.
9. The vast, three-dimensional expanse that contains all matter and energy in the universe.
10. A celestial body that orbits a star, is spherical in shape, and has cleared its orbit of other debris.
11. A small icy object that releases gas and dust as it approaches the sun, creating a visible tail.
15. A large group of galaxy clusters that are gravitationally bound together.
16. A region in space with such strong gravity that nothing, not even light, can escape from it.