The document contains definitions of several astronomy terms:
- Asteroid belt - The part between the inner and outer planets that is filled with asteroids.
- Axis - A straight line that an object or body rotates, or seems to rotate around.
- Blue moon - When there are two full moons in one month, which happens every 2 to 3 years.
- Asterism - Stars that form patterns but are generally smaller than or part of a constellation.
- Astronomy - The study of the Universe and all the bodies that appear in the skies.