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Henrietta Swan Leavitt

Data de nascimento: 4. Julho 1868
Data de falecimento: 12. Dezembro 1921

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Henrietta Swan Leavitt foi uma astrônoma estado-unidense famosa por seu trabalho sobre estrelas variáveis. Seus resultados foram utilizados por Edwin Hubble para calcular as distâncias das galáxias. Com isso, Hubble pôde mostrar que algumas destas "nebulosas" são na verdade outras galáxias, pondo fim a um longo debate sobre a natureza destes objetos e sobre as dimensões do Universo. O conhecimento das distâncias destes objetos permitiu ainda que Hubble concluísse que o Universo está em expansão, o que demonstra a importância dos trabalhos de Henrietta Leavitt.

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Citações Henrietta Swan Leavitt

„A straight line can readily be drawn among each of the two series of points corresponding to the maxima and minima, thus showing that there is a simple relation between the brightness of the variables and their periods.“

— Henrietta Swan Leavitt
Context: A remarkable relation between the brightness of these [Cepheid] variables and the length of their periods will be noticed. In H. A. 60, No.4, attention was called to the fact that the brighter variables have the longer periods, but at that time it was felt that the number was too small the drawing of general conclusions. The periods of 8 additional variables which have been determined since that time, however, conform to the same law. The relation is shown graphically in Figure 1... The two resulting curves, one for the maxima and one for the minima, are surprisingly smooth, and of remarkable form. In Figure 2, the abscissas are equal to the logarithms of the periods, and the ordinates to the corresponding magnitudes, as in Figure 1. A straight line can readily be drawn among each of the two series of points corresponding to the maxima and minima, thus showing that there is a simple relation between the brightness of the variables and their periods. The logarithm of the period increases by about 0.48 for each increase of one magnitude in brightness.

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„The discovery of variable stars“

— Henrietta Swan Leavitt
Context: The discovery of variable stars, at this Observatory and elsewhere, has progressed so rapidly during the last five years, that the difficulty of keeping pace in observing and discussing them has become very great. In the study of distribution now in progress here, the actual time devoted to the search for new variables is small, but thorough observation requires much time, while the discussion of results may be prolonged almost indefinitely. When new lists of variables are published, therefore, it should be remembered that their discovery does not interfere materially with the study of individual objects. The number of these is so large that the publication of full results for all must be greatly delayed. "Ten Variable Stars of the Algol Type" http://books.google.com/books?id=UkdWAAAAYAAJ&pg=PA87 (1908) Annals of the Astronomical Observatory of Harvard College Vol.60. No.5

„The range of H 1255 is only four tenths of a magnitude, and on account of its brightness it is difficult to observe on all plates except those taken with the 1-inch Cooke lens. It seemed necessary, therefore, to take unusual precautions in order to secure accurate observations, and to give each one its full weight. Accordingly, one hundred and thirty six photographs were selected, including nearly all of those taken with the Cooke lens, and also those taken with the 8 inch Bache Telescope on which the variable was certainly faint. Four independent estimates of brightness were made on each plate, and means were taken, thus reducing the probable error one half. The phase was computed for each observation, thus covering all parts of the light curve.... H 1255 and H 1303 differ from the other variables in a marked degree as in each case the duration of the phase of minimum is very long in proportion to the length of the period. This fact led to considerable difficulty in determining their periods as they were apparently at their minimum brightness for some time before and after the actual minima occurred. In H 1255, the change in brightness is obviously continuous throughout the period, although it is much more rapid near minimum than near maximum. This is clearly seen in Plate IV, Figs. 5 and 6.“

— Henrietta Swan Leavitt
"Ten Variable Stars of the Algol Type" http://books.google.com/books?id=UkdWAAAAYAAJ&pg=PA87 (1908) Annals of the Astronomical Observatory of Harvard College Vol.60. No.5

„It is worthy of notice that in Table VI the brighter variables have the longer periods. It is also noticeable that those having the longest periods appear to be as regular in their variations as those which pass through their changes in a day or two.“

— Henrietta Swan Leavitt
"1777 Variables in the Magellanic Clouds" http://books.google.com/books?id=UkdWAAAAYAAJ&pg=PA87 (1908) Annals of the Astronomical Observatory of Harvard College Vol.60. No.4, p.107