1.Describe the discoveries that confirmed the existence of galaxies that lie far

Question

1.Describe the discoveries that confirmed the existence of galaxies that lie far beyond the Milky Way Galaxy 2.Explain why galaxies used to be called nebulae and why we don’t include them in that category any more 3.Describe the properties and features of elliptical, spiral, and irregular galaxies 4.Describe the methods through which astronomers can estimate the mass of a galaxy 5.Describe the use of variable stars to estimate distances to galaxies 6.Explain how standard bulbs and the Tully-Fisher relation can be used to estimate distances to galaxies 7.Explain how to use Hubble’s law to determine distances to remote galaxies 8.Describe models for the nature of an expanding universe
1.Describe the discoveries that confirmed the existence of galaxies that lie far beyond the Milky Way Galaxy 2.Explain why galaxies used to be called nebulae and why we don’t include them in that category any more 3.Describe the properties and features of elliptical, spiral, and irregular galaxies 4.Describe the methods through which astronomers can estimate the mass of a galaxy 5.Describe the use of variable stars to estimate distances to galaxies 6.Explain how standard bulbs and the Tully-Fisher relation can be used to estimate distances to galaxies 7.Explain how to use Hubble’s law to determine distances to remote galaxies 8.Describe models for the nature of an expanding universe
2.Explain why galaxies used to be called nebulae and why we don’t include them in that category any more 3.Describe the properties and features of elliptical, spiral, and irregular galaxies 4.Describe the methods through which astronomers can estimate the mass of a galaxy 5.Describe the use of variable stars to estimate distances to galaxies 6.Explain how standard bulbs and the Tully-Fisher relation can be used to estimate distances to galaxies 7.Explain how to use Hubble’s law to determine distances to remote galaxies 8.Describe models for the nature of an expanding universe

Explanation / Answer

Answer-1:

By the 20th centuary many astronomers were able to some unknown nebulae. If these nebulae were nearby, with distances comparable to those of observable stars, they were most likely clouds of gas or groups of stars within our Galaxy. If, on the other hand, they were remote, far beyond the edge of the Galaxy, they could be other star systems containing billions of stars astronomers had to find a way of measuring the distances to at least some of them. When the 2.5-meter telescope on Mount Wilson in Southern California went into operation, astronomers finally had the large telescope they needed to settle the controversy. Working with the 2.5-meter telescope, Edwin Hubble was able to resolve individual stars in several of the brighter spiral-shaped nebulae, including, the great spiral in Andromeda. Among these stars, he discovered some faint variable stars that—when he analyzed their light curves—turned out to be cepheids. After painstaking work, he estimated that the Andromeda galaxy was about 900,000 light-years away from us. At that enormous distance, it had to be a separate galaxy of stars located well outside the boundaries of the Milky Way. Today, we know the Andromeda galaxy is actually slightly more than twice as distant as Hubble’s first estimate, but his conclusion about its true nature remains unchanged.

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