The branch of science that deals with celestial objects

A regular oval shape traced by a point moving in a plane

The mean distance from the center of the earth to the center of the sun

The force that attracts a body toward the center of earth

The action of rotating around an axis 

A forceable overthrow of a government 

The center of mass of two or more bodies that are orbiting each other

The slow movement of the axis of a spinning body around another axis

The inclination of the axis of a rotating object

The range of wavelengths 

The frequency of light, sound as the source moves to each other 

A patch appearing from time to time on the sun's surface.

A brief eruption of intense high-energy radiation from the sun's surface 

Atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy 

The observed expansion on the universe