Across
- 2. A cloud of gas and dust in outer space.
- 4. An ___ is composed of atoms that have the same atomic number.
- 5. What happened 13.8 billion years ago?
- 7. A what orbits around a star
Down
- 1. The charged central core
- 2. A proton or neutron.
- 3. A bright figure in the sky
- 6. stars, gas, and dust show signs or what?