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NGC 6302, also called the Bug Nebula, Butterfly Nebula, is a bipolar planetary nebula in the constellation Scorpius. The structure in the nebula is among the most complex ever observed in planetary nebulae. The spectrum of NGC 6302 shows that its central star is one of the hottest stars in the galaxy, with a surface temperature in excess of 200,000 K, implying that the star from which it formed must have been very large (''cf.'' PG 1159 star). The central star, a white dwarf, was only recently discovered , using the upgraded Wide Field Camera 3 on board the Hubble Space Telescope. The star has a current mass of around 0.64 solar masses. It is surrounded by a particularly dense equatorial disc composed of gas and dust. This dense disc is postulated to have caused the star's outflows to form a bipolar structure similar to an hour-glass. This bipolar structure shows many interesting features seen in planetary nebulae such as ionization walls, knots and sharp edges to the lobes. ==Observation history== As it is included in the New General Catalogue, this object has been known since at least 1888.〔Many sources credit its discovery to James Dunlop in 1826. E.g. (1) Wolfgang Steinicke, ''Nebel und Sternhaufen: Geschichte ihrer Entdeckung, Beobachtung und Katalogisierung- von Herschel bis Dreyers'', 2009, p.429. (2) (Universe Today ); (3) (Stephen James O'Meara, ''The Caldwell objects''. Cambridge University Press, 2002, p.274. ). (O'Meara argues that Barnard credited it to Dunlop - but may have been mistaken.)〕 The earliest known study of NGC 6302 is by Edward Emerson Barnard, who drew and described it in 1907 . Since then it has been the focus of many works and displays many interesting characteristics worthy of study. Interest in recent years has shifted from discussions over the excitation method in the nebula (shock-excitation or photo-ionisation) to the properties of the large dust component. It featured in some of the first images released after the final servicing mission of the Hubble Space Telescope in September 2009.〔News Release Number: STScI-2009-25: Hubble Opens New Eyes on the Universe ()〕 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「NGC 6302」の詳細全文を読む スポンサード リンク
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