褐かっ色しょく矮わい星せい

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Meanings

1

noun

brown dwarf

astronomy

Astronomy term for a substellar object that is not massive enough to sustain hydrogen fusion.

褐かっ色しょく矮わい星せい

Standard kanji spelling for 'brown dwarf'.

褐かっ色しょくわい星せい

Mixed kanji-kana spelling; less common but still used.

恒こう星せい
恒星 is a star that sustains hydrogen fusion, while 褐色矮星 is a substellar object that cannot sustain fusion.
惑わく星せい
惑星 is a planet, which orbits a star and does not produce its own energy through fusion, unlike a brown dwarf which may have limited deuterium fusion.

褐色 (brown) + 矮星 (dwarf star). A calque of English 'brown dwarf'.