Comparing planets

2. A large grouping of stars in space
6. In comparison to something else
9. The study of celestial objects, space, and the universe as a whole
10. The shape of the illuminated portion of the Moon as seen by an observer, usually on Earth
12. A scientist who studies objects in space
13. The movement of one object around a center or another object

1. The galaxy in which Earth and the Sun are
3. Large and small rocks or metallic masses orbiting the Sun.
4. A curved path followed by a satellite as it revolves around an object
5. The layer of gas surrounding a planet that is held in place by gravity
7. A large celestial body that revolves around a star in a solar system
8. Outer planets made mostly of gases
11. A celestial body of ice, dust, and rock with an elongated and elliptical orbit