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Shvoong Home>Science>article - Recent red shifts Summary

article - Recent red shifts

Article Summary   by:PG Aasis Vinayak     Original Author: Aasis Vinayak P G
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Welcome to the high-red shift era The Hubble Deep Fields clutch the key to appreciate how galaxies shape and develop especially in this aspect they are having a similar effect on the subject of galaxy creation to that of the remnant evidence on our perceptive of the origin of the species and the evolution of life. The Hubble Deep Field images provide the angular locations of about more than 5000 galaxies, but it does not give any clear information regarding their distances (or red shifts). Data of distance is very significant for calculating all the information hidden in the images, but computing all the red shifts directly by taking a spectrum for each galaxy would be a very time-consuming mission. Also, many of the galaxies are very faded for their spectra to be measurable even with a telescope as large as Keck. A new key to the problem of calculating distances to far-away galaxies was initiated by Chuck Steidel of the California Institute of Technology and collaborators in the early 1990s. Galaxies have to give out light over a wide range of wavelengths, and the thermal radiation from hot stars and in addition to this, the line emission from helium and other heavier elements can broaden well into the ultraviolet. On the other hand, Steidel and co-workers documented that the ultraviolet spectrum of a distant galaxy would drop stridently to roughly zero at wavelengths below 912 angstrom, the wavelength equivalent to the ionization energy or Lyman limit of hydrogen.
This phenomenon which is popular as a "break” happens due to the reason that the lion share portion of photons emitted at higher frequencies are absorbed by hydrogen atoms in the galaxy itself or by hydrogen clouds that exist between the distant galaxy and us. Consequently, the spectrum of a distant galaxy will exhibit a break at the wavelength matching to the red shifted Lyman limit. Steidel and his associates deployed a series of filters that only transmitted light in a collection of wavelengths about 500-1000 angstrom wide to watch galaxies. The application of the Lyman-break technique offered the first models of indisputably high-red shift galaxies. Using this simple "Lyman break" scheme, large numbers of high-red shift galaxies were recognized and their individual spectra were then measured with the Keck telescope. Universe simulationsRecent works of the dynamics of galaxies substantiate a primary deduction made 25 years ago from analyzing the kinematics of stars within galaxies, that is to say, on scales larger than galactic nuclei, the central physical interaction is gravity.
Published: April 25, 2006   
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