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- Be_star abstract "A B(e) star is a B-type star with distinctive forbidden neutral or low ionisation emission lines in its spectrum. The designation results from combining the spectral class B and the lowercase e denoting emission in the spectral classification system. These stars frequently also show strong hydrogen emission lines, but this feature is present in a variety of other stars and is not sufficient to classify a B(e) object. Other observational characteristics include optical linear polarization and often infrared radiation that is much stronger than in ordinary B-class stars, called infrared excess. As the Be nature is transient, Be stars might exhibit a normal B-type spectrum at times, and hitherto normal B stars may become Be stars.While most Be stars are on the main sequence, the identifier actually refers to a heterogeneous group of objects including pre main sequence stars, supergiant stars, protoplanetary nebulae, and others. They may be subclassed into B[e] supergiants (notation sgB[e]), Herbig Be stars, compact planetary nebula B[e], symbiotic B[e], and a catch-all "unclear" category.The first star recognized as a Be star was Gamma Cassiopeiae, observed 1866 by Angelo Secchi, the first star ever observed with emission lines. With the understanding of the processes of emission line formation in the early 20th century it became clear that these lines must come from the circumstellar environment, not from the star itself. Nowadays, all the observational characteristics are explained with a gaseous disk that is formed of material ejected from the star. The infrared excess and the polarization result from the scattering of stellar light in the disk, while the line emission is formed by re-processing stellar ultraviolet light in the gaseous disc.The forbidden emission, infrared excess, and other features indicative of the B(e) phenomenon, themselves provide strong hints at the nature of the stars. These are produced from circumstellar discs of material, most likely ejected or stripped from the stars themselves. B(e) stars frequently rotate rapidly, which has been confirmed by interferometric measurements of the rotational distortion of Achernar. However, rotation alone is probably not sufficient to form the disk, but an additional ejection mechanism is required, such as a magnetic field or nonradial stellar pulsation. The transient nature of the Be phenomenon is most likely connected to the nature of that secondary process, but the details are currently still being discussed. The heterogeneous nature of the group of B(e) stars suggest a heterogeneous mechanism for formation of the discs. Many supergiant B(e) stars have been shown to be involved in binary systems where the companion may contribute to periodic ejection of material, or are unstable highly luminous stars which have continuum driven winds.Be stars are typically variable and can either be classified as Gamma Cassiopeiae variable due to the transient nature of the disk and the scattering processes, or as Lambda Eridani variable on account of their pulsational nature.".
- Be_star thumbnail Achernar.jpg?width=300.
- Be_star wikiPageExternalLink eso1306.
- Be_star wikiPageExternalLink page3.html.
- Be_star wikiPageExternalLink be_stars.html.
- Be_star wikiPageID "255463".
- Be_star wikiPageRevisionID "540346518".
- Be_star hasPhotoCollection Be_star.
- Be_star subject Category:Be_stars.
- Be_star subject Category:Star_types.
- Be_star type BeStars.
- Be_star type CelestialBody109239740.
- Be_star type NaturalObject100019128.
- Be_star type Object100002684.
- Be_star type PhysicalEntity100001930.
- Be_star type Star109444100.
- Be_star type Whole100003553.
- Be_star comment "A B(e) star is a B-type star with distinctive forbidden neutral or low ionisation emission lines in its spectrum. The designation results from combining the spectral class B and the lowercase e denoting emission in the spectral classification system. These stars frequently also show strong hydrogen emission lines, but this feature is present in a variety of other stars and is not sufficient to classify a B(e) object.".
- Be_star label "Be star".
- Be_star label "Be-Stern".
- Be_star label "Be-звезда".
- Be_star label "Be星".
- Be_star label "Be星".
- Be_star label "Estrella Be".
- Be_star label "Stella Be".
- Be_star label "Étoile Be".
- Be_star sameAs Be-Stern.
- Be_star sameAs Estrella_Be.
- Be_star sameAs Be_izar.
- Be_star sameAs Étoile_Be.
- Be_star sameAs Stella_Be.
- Be_star sameAs Be星.
- Be_star sameAs 비이형_별.
- Be_star sameAs m.01lvs0.
- Be_star sameAs Q812800.
- Be_star sameAs Q812800.
- Be_star sameAs Be_star.
- Be_star wasDerivedFrom Be_star?oldid=540346518.
- Be_star depiction Achernar.jpg.
- Be_star isPrimaryTopicOf Be_star.