Space

4. A powerful stellar explosion.
6. An object that orbits a planet or star.
7. A cloud of gas and dust in space.
12. The branch of astronomy dealing with the physics of celestial bodies.
13. A small body from space that enters Earth's atmosphere, creating a streak of light.
15. A group of stars forming a recognizable pattern.
17. A celestial body of ice, dust, and rock with a glowing coma.
19. A highly magnetized rotating neutron star that emits beams of electromagnetic radiation.
20. The study of celestial objects and phenomena.

1. The universe seen as a well-ordered whole.
2. A celestial body orbiting a star, large enough to be rounded by its gravity.
3. A massive system of stars, gas, and dust held together by gravity.
5. All existing matter and space as a whole.
8. A region of space with a gravitational pull so strong that nothing can escape.
9. The study of the origin and development of the universe.
10. A small rocky body orbiting the Sun.
11. A highly luminous and active galactic nucleus.
14. A luminous sphere of plasma held together by gravity.
16. The curved path of an object around a star, planet, or moon.
18. A planet outside our solar system.