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HD 5980 is a multiple star system in NGC 346 in the Small Magellanic Cloud (SMC) and is one of the brightest stars in the SMC. HD 5980 has at least three components amongst the most luminous stars known: the unusual primary has a Wolf–Rayet spectrum and has produced a luminous blue variable (LBV) outburst; the secondary, also a Wolf–Rayet star, forms an eclipsing spectroscopic binary with the primary star; and a more distant O-type supergiant is also likely to be a binary. ==Discovery== HD 5980 was first recorded in 1901 as the first object in a list of southern sky objects having peculiar spectra. It was described as "Type V", referring to the Secchi class for stars with emission lines. It was formally named HD 5980 in the first Henry Draper Catalogue where it was given the spectral type of Oa indicating strong emission bands. The spectral type was later refined to Wa when the emission line "O" stars were recognised as a separate class. Later observations detected spectral and brightness variations and eclipses, but it was thought to be a simple WR/OB binary. Absorption lines in the spectrum that did not move during the binary orbit eventually led to the conclusion that HD 5980 was a triple system with a close eclipsing binary and a more distant class O supergiant. In 1993, the spectrum began to change and the brightness increased, beginning a dramatic change that has been interpreted as a unique type of LBV eruption.〔 Since then the star has been intensively observed and modelled.〔 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「HD 5980」の詳細全文を読む スポンサード リンク
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