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A Method of Determining Stellar Rotation*

    Naturevolume 140page162 (1937) | Download Citation



    WHILE rotational speeds of stars can be estimated from photographs of stellar spectra, the actual deduction of these speeds and the demonstration that the star is rotating depend on rather abstruse mathematical calculation which, however, leads to a comparatively simple working routine. A knowledge of stellar rotational speeds, while obviously worth determining in any event, has several immediate applications, such as assessing the age of the stellar system, and is especially important in discussing the state of affairs in stellar atmospheres, a high rotational speed tending to offset gravity and promote ionization. If the rotational speed of a star is determinable, then the 'proper' spectrum of the star can be deduced ; that is, the light emitted by any element of the star's surface, as distinct from the 'integrated' spectrum directly observed. Owing to the minuteness of a stellar image in a telescope, the light from the whole of the star's surface passes into the spectroscope, and the rotational speed of a star cannot be measured as can that of the sun by observing the Doppler displacement of the Fraunhofer lines from one limb as compared with the other.


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      Mon. Not. Roy. Alt. Soc.. 93, 478, 508, 680 (1933).

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