Modern Astronomy

2. The perimeter of a circle or ellipse.
7. Earth does this around the sun once a year.
8. An obscuring of the light from one celestial body by the passage of another between it and the observer or between it and its source of illumination.
11. His accurate measurements of Mars were his greatest contributions to astronomy.
14. Are three scientific laws describing the motion of planets around the Sun, by Johannes Kepler.
15. Dark region of the Sun due to lower temperature.

1. It is the shape of the Earth and some other planets; sphere squashed at the poles.
3. A representation of the sun–Earth–moon system.
4. Justified his Earth-centered model and explained retrograde motion through cycles and epicycles.
5. Developed and formalized Galileo's concept of inertia.
6. Developed a heliocentric system wherein the orbits were elliptical rather than circular.
9. A displacement or difference in the apparent position of an object viewed along two different lines of sight.
10. Earth's path in space
12. An imaginary line through Earth.
13. Discovered by Galileo to look at the moon, discover the four satellites of Jupiter, observe supernova, and discover sunspots.