| A | B |
|---|
| astronomy | the study of the stars and other heavenly bodies |
| satellite | a body that moves around a larger one in space |
| navigator | a person who is trained to guide a ship or airplane from one place to another |
| astronomer | a person who studies astronomy |
| telescope | a tool used to study distant objects |
| antenna | a tool used to receive radio waves |
| spectroscope | a tool used to break up light so it can be studied |
| refract | to bend |
| refracting telescope | a telescope that uses only lenses |
| convex lens | a lens that is thicker in the middle than at the edges |
| objective lens | a lens that collects light and brings it to a focus |
| focus | a point where light rays are brought together |
| eyepiece lens | a lens that acts like a magnifying glass |
| reflecting telescope | a telescope that uses a mirror to collect light |
| concave mirror | a mirror that is curved inward |
| magnitude | a measure of the brightness a star appears to have |
| astronomical unit | a unit of distance that astronomers use; it is about 150 million kilometers |
| light-year | the distance light can travel in one year; one light-year equals about 10 trillion kilometers |
