Quasars Essay -- Essays Papers

Quasars Since their discovery, the nature of quasars has been one of the most intriguing and baffling problems as evidenced by the following quotations: " the problem of understanding quasi-stellar objects†¦ is one of the most important and fascinating tasks in all physics" - G.Burbidge and Hoyle. "The quasar continues to rank both as one of the most baffling objects in the universe and one most capable of inspiring heated argument" - Morrison. "The redshift problem is one of the most critical problems in astronomy today" - G. Burbidge. "Quasars still remain the profoundest mystery in the heavens" - Hazard and Mitton. The conventional interpretation of the spectral lines observed in quasars is based on the redshift hypothesis. Three hypotheses have been advanced to account for the supposed redshifts: 1. Cosmological hypothesis; the redshifts are due to the expansion of the universe, 2. Gravitational hypothesis, 3 Local-Doppler hypothesis; in this hypothesis the redshifts are due to the Doppler effect, but the quasars are relatively nearby and have nothing to do with the expansion of the universe. Of these hypotheses, the first one is the most publicized one. One is led to attribute to quasars very many mysterious properties if one assumes the redshift hypothesis to be correct. A patient analysis of the data on quasars over the years has led to the conclusion that the real source of the trouble is in the assumption that the spectra of quasars have redshifts. In the early 1960's quasars were known as 'radio stars' because the method used to discover the first quasars was based on coincidences between a strong radio source and a point-like optical source. Since each radio source was associated with a star it was originally thought that quasars were objects within the galaxy hence the term 'radio stars'. Quasars or quasi-stellar radio source, from the method by which they where originally discovered: as stellar optical counterparts to small regions of strong radio emission. With increasing spatial resolution of radio telescopes the strong radio emission often seemed to come from a pair of lobes surrounding many of these faint star-like emission line objects. The initial method of selection was strong radio emission, and then later any object with blue or ultraviolet excess wa... ... between galaxies, either through direct collisions or near encounters, can be important in turning on a quasar, by dumping fuel onto a black hole. However some quasars look unperturbed, so there may be other, more subtle mechanisms for feeding the black hole. Some of the galaxies we observed don't appear to know they have a quasar in their core. 3. Quasars that are radio quiet are often in elliptical galaxies, not always in spiral galaxies, as previously believed. Advanced instruments planned for Hubble should also help pin down more details. The Near Infrared Camera and Multi-Object Spectrometer (NICMOS), to be installed in 1997, and the Advanced Camera, to be installed in 1999, will have coronagraphic devices which will block out the glare of a quasar, allowing astronomers to see closer into a galaxy's nucleus. By viewing galactic structures in infrared light , the NICMOS should be able to provide important new details about the host galaxies of quasars. The continued study of quasars and the information that it will provide us with may help us to develop a better understanding of space and how we fit in to this great puzzle.