What is the main characteristic of a celestial body's albedo?

The main characteristic of a celestial body's albedo is the amount of light the body reflects. Albedo is a measure of reflectivity, indicating how much sunlight or other radiation is reflected by a surface back into space. It is expressed as a fraction or percentage, where a higher albedo means that the body reflects more light, while a lower albedo indicates that more light is absorbed.

For example, snow has a high albedo because it reflects most of the sunlight that hits it, whereas darker surfaces like oceans or asphalt have a lower albedo because they absorb more light. Understanding a celestial body's albedo is crucial for studying its surface properties, temperature, and climate, as it affects the body’s energy balance and thermal characteristics.

The other choices do not pertain directly to the concept of albedo, as they relate to physical attributes that do not define reflectivity. Hence, the correct answer is based on the pivotal role that albedo plays in light and energy interactions with celestial bodies.