Light hour

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A light hour (also written light-hour) is a unit of length. It is the distance travelled by light in vacuum in one hour. Based on the current definition of the metre a light-hour is equal to 1,079,252,848,800 metres (~1.08 Tm).

This distance can easily be related to the speed of light in kilometres per hour, since light travels 1,079,252,848,800 m every hour, or 1,079,252,848.8 km/h.

To give an example, Pluto's orbit's semi-major axis is about 5.473 light-hours.

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