Across
- 4. a theory that our universe began with a primordial explosion some 13.7 billion years ago
- 5. mercury,venus,earth,mars are all
- 8. hottest planet
- 9. what remains when a supergiant star collapses into itself
- 10. Jupiter,saturn,uranus,neptune are all
Down
- 1. a graph of intrinsic brightness versus surface temperature for stars
- 2. a huge assemblage of stars, interstellar gas, and dust
- 3. groups of stars with names from antiquity
- 6. a cloud of gas and dust
- 7. closest planet to the sun