universe

4. The average distance from Earth to the Sun
7. The imaginary north-south line that passes directly overhead
9. A telescope’s main light-gathering lens or mirror.
10. When the Moon or other body appears more than half, but not fully, illuminated
12. The edge of a celestial object’s visible disk.

1. The fraction of the Moon or other body that we see illuminated by sunlight.
2. When the Moon or a planet appears especially close either to another planet or to a bright star.
3. Two stars that lie very close to, and are often orbiting, each other
5. The circle of sky that you see when you look through a telescope or binoculars
6. the second full Moon in a single calendar month
8. The measure of how much an orbit deviates from being circular
11. A star ending its life in a huge explosion.