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      , {"_about" : "http://astrothesaurus.org/uat/739", "narrower" : ["http://astrothesaurus.org/uat/1447"]}
      ], "contributor" : "http://editor.vocabs.ands.org.au/user/AAS_Frey.Katie_Admin", "dctermsModified" : "Wed, 04 Nov 2020 14:47:16 GMT+0000", "definition" : "A member of an important class of active galaxies which are characterized by the presence of an intensely bright nucleus in the optical wavelengths (10^9-10^12 L_sun) displaying emission spectral lines. The presence of these emission features, which are not seen in the spectra of normal galaxies, indicates a very high degree of ionization. Moreover, the nucleus radiates non-thermal continuum emission extending over the whole electromagnetic spectrum. It is thought that a massive black hole in the nucleus of a galaxy accretes gas (accretion) from its surrounding environment to power Seyfert galaxies. These galaxies are divided into two types according to the width of their spectral lines. Type 1 Seyfert (Sy 1) galaxies have very broad emission lines (10^3 - 10^4 km s^-1), while Type 2 Seyferts (Sy 2) show relatively narrow lines (several hundred km s^-1). These spectral differences may be the result of viewing the nucleus from different angles. A Type 2 Seyfert galaxy may be a mostly edge-on view of matter spiraling in toward the supermassive black hole, whereas a Type 1 Seyfert provides a more pole-on view, allowing us to see the more turbulent region around the black hole.", "prefLabel" : {"_value" : "Seyfert galaxies", "_lang" : "en"}
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