Light-second

A light-second is a unit of length equal to the distance light in empty space travels in one second, and is exactly 299,792,458 meters.^[1]

The light-second is used in telecommunications, astronomy, and physics. In telecommunications, it measures how much time it must take to send a signal a certain distance.

Light-second Media

The yellow shell indicating one light-day distance from the Sun compares in size with the positions of Voyager 1 and Pioneer 10 (red and green arrows respectively). It is larger than the heliosphere's termination shock (blue shell) but smaller than Comet Hale-Bopp's orbit (faint orange ellipse below).
The faint yellow sphere centred on the Sun has a radius of one light-minute. For comparison, sizes of Rigel (the blue star in the top left) and Aldebaran (the red star in the top right) are shown to scale. The large yellow ellipse represents Mercury's orbit.

References

↑ International Bureau of Weights and Measures (2006), The International System of Units (SI) (PDF) (8th ed.), p. 112, ISBN 92-822-2213-6

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[1] International Bureau of Weights and Measures (2006), The International System of Units (SI) (PDF) (8th ed.), p. 112, ISBN 92-822-2213-6

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