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The gigametre (official spelling used by the International Bureau of Weights and Measures;〔(【引用サイトリンク】url=http://www.bipm.org/en/CGPM/db/17/1/ )〕 SI symbol: Gm) or gigameter (American spelling) 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. They are too big for any terrestrial lengths, and gigametre distances in astronomy (e.g. a planet's distance from its star) are usually given in astronomical units (AU) or in (millions of) kilometres. * Earth's average distance from the Sun is 149.6 Gm or 1 AU. * 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 1,302 Gm. == See also == * 1 E+9 m * Conversion of units, for comparison with other units of length * Light year * Metric system * Orders of magnitude (length) * Parsec * SI * SI prefix 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gigametre」の詳細全文を読む スポンサード リンク
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