Ashleywng
09.05.2013., četvrtak
Lorentz contraction and Grand Unification
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Such clouds are found all over the sky, often in large agglomerations the width of the Big Dipper, or greater. They have been explained as immense gas clouds between galaxies (some possibly associated with galaxies too faint to see) or alternatively, rapidly expanding gas shells from supernova explosions within the disk of our galaxy. Duncan. “We are very pleased with the quality of the data," says Hartig. Astronomers reported today that recent ultraviolet observations with NASA's Hubble Space Telescope suggest that what were thought to be randomly distributed, nearby primordial clouds of hydrogen may actually be associated with galaxies or clusters of galaxies. Bahcall, Buell Jannuzi and Donald Schneider, all of the Institute for Advanced Study and George Hartig of the Space Telescope Science Institute, Baltimore, MD, announced their results today to a press conference at the 179th meeting of the American Astronomical Society in Atlanta. Where did the cloud come from? "It is not pristine. Ground-based observations have shown that the number of these clouds rapidly rises as one looks back in time, so it was thought, says Hartig Tricor 160Mg the number of nearby hydrogen clouds was relatively small. Using HST's Goddard High Resolution Spectrograph, the researchers detected traces of boron in a yellow 7th magnitude star called HD 140283, located inactive light-years away in the constellation Libra. Astronomers have assumed that the clouds are strung along the line-of -sight to a quasar, like beads on a string. A foreground galaxy that lies along the line of sight to the quasar has the same distance from us as does one of the cloud groupings. Danly found that a high velocity cloud complex called M, lies between a pair of stars in the Milky Way's halo. The new results are based upon Faint object Spectrograph observations of a bright and relatively nearby (approximately four Order Tricor No Prescription light-years distant) quasar H1821+643. HST spectra of other nearby quasars are being obtained to see if there is additional evidence of clumping of the hydrogen clouds or if any other absorption systems can be identified as belonging to galaxies. At an estimated age of 15 billion years, the star is one of the oldest known inactive . Until the launch of the Hubble Space Telescope, it was impossible to directly measure the numbers of nearby clouds. These types of lines, called self- absorption systems, have been found in high-redshift quasars and were thought to be produced by material in the quasar itself. The clouds have only been seen previously in the emission of neutral hydrogen (2l- cm) which could arise anywhere along the line of sight. If so, then one of astronomy's many current mysteries may at last be solved. One grouping of lines in the complex spectrum has the same redshift, and hence the same distance, as the quasar. |
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