astronomy

4. Great clouds of glowing gas, lit up by stars inside, behind, or nearby.
5. A vast collection of stars, gas, and dust, typically 10,000 to 100,000 light-years in diameter and containing billions of stars.
8. A “dirty snowball” of ice and rocky debris, typically a few miles across, that orbits the Sun in a long ellipse.
9. The envelope of gases surrounding the earth or another planet.
11. A star ending its life in a huge explosion.
12. A supermassive black hole gorging on gas at the center of a distant galaxy.

1. A broad, faintly glowing band stretching across the night sky, composed of billions of stars in our galaxy too faint to be seen individually.
2. The distance that light travels in one year, or about 6 trillion miles.
3. A concentration of mass so dense that nothing — not even light — can escape its gravitational pull once swallowed up.
6. A solid body orbiting the Sun that consists of metal and rock.
7. An event that occurs when the shadow of a planet or moon falls upon a second body.
10. A brief streak of light caused by a small piece of solid matter entering Earth’s atmosphere at tremendous speed; also called a "shooting star".
11. A massive ball of gas that generates prodigious amounts of energy (including light) from nuclear fusion in its hot, dense core.