Which of the following describes altitude in the context of astronomy?

Altitude in the context of astronomy refers to the angular distance between the observer's local horizon and a celestial body, such as a star or planet. Essentially, it measures how high above the horizon the object appears in the sky. An altitude of 0° means the object is on the horizon, while an altitude of 90° indicates that the object is directly overhead. This measurement is an important part of the altazimuth coordinate system used to pinpoint objects in the sky from a specific location on Earth.

The other options do not pertain to the definition of altitude. The distance from the Sun relates to the positioning of celestial bodies in the solar system, while the speed of celestial bodies refers to their motion rather than their position in the sky. The time taken for a planet to orbit the Sun pertains to orbital mechanics and doesn't describe the spatial orientation of celestial objects as altitude does. Thus, the correct answer is accurately aligned with the fundamental understanding of altitude in astronomy.