|This article does not cite any references or sources. (December 2009)|
|1.000×106 km||1.000×109 m|
|6.685×10−3 AU||105.7×10−9 ly|
|US customary / Imperial units|
|621.4×103 mi||3.281×109 ft|
A gigametre (American spelling: gigameter, symbol Gm) is a unit of length in the metric system, equal to one billion metres, the SI base unit of length, hence to 1,000,000 km or approximately 621,370 miles.
Gigametres (from the Greek words gigas = giant and metro = count/measure) are rarely seen in practical use, because they are too big for any terrestrial tasks. However, gigametres are sometimes used in astronomy to measure the distance of companion objects such as planets from their stars including our Sun alongside with astronomical units (AU).
- One astronomical unit (AU) or Earth's average distance from the Sun is 149.6 Gm.
- Jupiter's average distance from the Sun is 778.5 Gm.
- PSR J1719-1438 b's average distance from the pulsar PSR J1719-1438 is 0.666 Gm, which is the smallest orbit of any known exoplanets.
- The mean diameter of the Sun is 1.393 Gm.
- The mean diameter of red supergiant star Betelgeuse is 1302 Gm.
 See also
- 1 E+9 m
- SI prefix
- Metric system
- Orders of magnitude (length)
- Conversion of units, for comparison with other units of length
- Light year
- Emilio, Marcelo; Kuhn, Jeff R.; Bush, Rock I.; Scholl, Isabelle F. (March 5, 2012), "Measuring the Solar Radius from Space during the 2003 and 2006 Mercury Transits", arXiv, retrieved March 28, 2012