| A | B |
|---|
| microgravity | occurs in an environment such as a spacecraft, where gravity has little or no measurable effect |
| planets | celestial bodies in our solar system that orbit the Sun |
| inner planets | the four planets closest to the Sun; they have rocky compositions |
| outer planets | the four planets furthest from the Sun; they have gaseous compositions |
| mass | the amount of matter in a substance |
| relative size | a way of describing an object's size in comparison with another's |
| star coordinates | refer to a celestial body's measured location in the sky, relative to the Earth |
| altitude | measured in degrees, a celestial body's angle above the horizon |
| azimuth | measured in degrees, a celestial body's clockwise angle from North |
| geosynchronous orbit | an orbit around the Earth that matches the Earth's 24-hour rotation period |
| triangulation | a way of measuring distance by creating an imaginary triangle between two points |
| geocentric view | an "Earth-centred" view that places Earth at the centre of the universe with everything else revolving around it |
| heliocentric view | an "Sun-centred" view that places the Sun at the centre of the universe with everything else revolving around it |
| spectral analysis | a scientific method of determining which gases exist in the Sun's atmosphere by studying spectral lines |
| star | a massive, luminous celestial body composed of gases |
| satellite orbit | The curved path, usually elliptical, described by a satellite about the Earth |
