Word: star
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Dates: during 1920-1929
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...greatest problems that confronts astronomers at the present time is an accurate knowledge of the distances of stars. From the earliest times, the relative positions of stars or their apparent directions in space have been observed and measured with increasing accuracy. Before anything definite could be learned, however, as to the actual structure of the sidereal universe in which the earth plays its ultra-microscopic part, the actual distance to many of the brighter stars had to be measured. When Copernicus promulgated the heliocentric theory in 1543 through the publication of his epoch-making book. 'De Revolution-ibus Orbium Coelestium...
...case of a star of unknown distance whose spectrum has been photographed, the relative intensity of the lines is compared with a standard reduction curve, and the star is at once recognized as of a certain luminosity or absolute magnitude. The apparent brightness of this star, however, as seen from the earth will depend on its distance from us. The apparent brightness or magnitude is then determined either visually or photographically; and, knowing the actual brightness, the distance of the star is computed on the basis of the well known law of physics that the intensity of light varies inversely...
...miles which correspond to these parallax determinations tax the imagination to conceive. The contributions of astronomy in interpreting the sky and the earth's plane in the universe have exerted a profound influence on men's thinking in all ages'. For this reason, perhaps, astronomy makes so the casual star gazer who has learned to recognize familiar groups and the brighter planets...
...south at sundown is Jupiter, the brightest object in its neighborhood. A short distance to the west of Jupiter is Saturn. These two planets may be distinguished from the bright star Spica, which lies below Jupiter and Saturn and a little to the eastward, by the steadiness of the light emitted,--a characteristic feature of planets as compared with the more distant stars. Jupiter and Saturn are the two largest planets of the solar system, and are well situated for observation with telescopes of moderate size...
Mars now rises in the southwest about 9 P. M. and is conspicuous as a bright red star. On the tenth of June it will be in opposition with the sun, and will then be at the nearest distance to the earth that it has been for thirteen years. On that date the planet will be 42,000,000 miles from the earth. The nearest possible approach of the earth and Mars is 35,000,000 miles, and the farthest distance separating these two planets may be as great as 240,000,000 miles. This present opposition and the next...