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RE: RE: RE: Things Far Away

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Posted by Michael Wright on September 20, 2000 18:36:25 UTC

To answer your query about quasars, it is necessary to lay down the fact frist...

QUASARs, or QUAsi StellAR objects, are the very active cores in the center of galaxies at very large red-shifts, about 10% of the universe`s age or so. A few thousand have been discovered so far, and in most cases the quasar is so distant the host galaxy is invisible.

Some of the similarities between quasars and black holes in the center of galaxies are as follows:
-some quasars (3C 273 for example) show jest of material much like the jets from some supermassive black holes.
-Some quasars have associated radio lobes, much like supermassive black holes.
-Evidence leads astronomers to suspect that quasars are the erupting cores of very distant galaxies triggered into activity by collisions with other galaxies. If they are the cores of distant galaxies (galaxies of the early universe), this raises questions about whether or not they evolve into, or are themselves, the supermassive black holes in the galaxies near to us (galaxies in the recent past).

I have looked into astronomy textbooks, and I found a model of a quasar... "A model to account for the quasar phenomenon is based on disk-jet geometry... In the heart of a galaxy, matter flows into a hot accretion disk around a black hole containing at least a million solar masses. Radiation from the accretion disk and jets ejected along the axis of rotation heat the surrounding gas and turn the galaxy into a quasar."

In another book I found this: "To make the energy typical of a quasar we need a black hole of 10 million to a billion solar masses surrounded by a large, opaque disk. The innermost part of the accretion disk, much less than a light-year in diameter, would be intensely hot. If matter amounting to about 1 solar mass per year flows through the accretion disk into the black hole, the energy released could power a quasar."

The emission lines of a quasar don`t fluctuate rapidly, suggesting they are produced in a large region. They are probably emitted by clouds of gas surrounding the core in a region many light-years in diameter and excited by the intense synchrotron radiation streaming out of the central cavity.

The different kinds of quasars depend on how they are pointed towards us, as the angle of the quasar in relation to us determines what kinds of radiation we detect.

Many quasars are found in distorted galaxies that are interacting with nearby companions. This could throw matter into a supermassive black hole and trigger a quasar outburst. IRS 00275-2859, PG1613, and Markarian 231 are examples.

From my readings, I have found that quasars are not objects in the sense that black holes are objects; they are sources of energy seen at high red-shifts (but not too high, because galaxies need to have formed) when space had not expanded as much and when the galaxies were much closer to one another).

I know it is a long read (and a tough one if you are not familiar with astronomy), but I hope I helped out.

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