Word: cepheids
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Shapley explained that astronomers have long had doubts about the yardstick they use to measure the enormous distances between the galaxies. It is based on Cepheid variable stars, whose luminosity (and therefore whose distance) can be told from their periods of pulsation. The system worked all right for a while, but recently many contradictions have shown up. For instance, the globular star clusters in the Magellanic Clouds (small, comparatively nearby galaxies) seemed to be much fainter intrinsically than similar clusters in the Milky Way. This offended the astronomers' sense of order. They felt that the clusters in both galaxies...
Instead, astronomers at Harvard and at Mt. Palomar, gathering evidence with "ordinary" telescopes and re-analyzing old data have shown that classical Cepheid variable star are actually brighter than had been assumed. Knowing the absolute or intrinsic brightness of these particular stars, and from their apparent brightness, astronomers can determine the distances of nearby galaxies. The new results show that these stars are brighter than previously suspected, so that the distances of the galaxies are about twice their older values. Thus the part of the universe that astronomers have probed has about eight times the volume they had thought...
...Harrison Joy plotted the rotation of the Milky Way-the great star galaxy, six hundred thousand trillion miles across, to which the sun and all other visible stars belong. The regions near the centre of the galaxy are rotating fastest, the outermost regions slowest. By measuring the speeds of Cepheid variable stars, Professor Joy found that the region of the sun, two-thirds of the distance from the centre, rotates once every 207,000,000 years...
Super-Galaxies & Cepheids. Astronomer Harlow Shapley of Harvard, who loves to systematize the universe, was the first man to find that stellar galaxies like the Milky Way, each containing billions of stars, were sometimes huddled in groups which he calls "super-galaxies." Last week he reported the discovery, made by astronomers at Harvard's observatory in South Africa, of two new, far-off super-galaxies, each of which is about 1,000,000 light-years in diameter (one light-year equals approximately six trillion miles). Another discovery, nearer home, concerned the Cepheid variables-a class of stars, mostly yellow...
Shapley said that the "newly found prenomenon" of Cepheid distribution may prove to be "an indicator of gravitational potential throughout a galaxy." However, there may be another, alternative explanation of the peculiar distribution, involving the distribution of various chemical substances in the Magellanic Cloud, Shapley said. There is a possibility that the chemical distribution of the cloud is such that the large stars were found in densely populated star areas...