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The closest Quasar remenant is probably the quiet black hole at the centre of our own galaxy although it was probably not a very powerful one because it is omy measured in millions and not billions of solar masses.
Some quasars display changes in luminosity which are rapid in the optical range and even more rapid in the X-rays. This implies that they are small (Solar System sized or less) because an object cannot change faster than the time it takes light to travel from one end to the other; but relativistic beaming of jets pointed nearly directly toward us explains the most extreme cases. The highest redshift known for a quasar (as of December 2007) is 6.43, which corresponds (assuming the currently-accepted value of 71 for the Hubble Constant) to a distance of approximately 28 billion light-years. (N.B. there are some subtleties in distance definitions in cosmology, so that distances greater than 13.7 billion light-years, or even greater than 27.4 = 2x13.7 billion light-years, can occur.)
Putting a one million solar mass black hole into the scale of things. It is about twice the diameter of the sun or a few light seconds acrossFew people realise quite how small black holes realy are and how difficult it would be to fall into them from a distance if there was nothing in the way.even the very most massive black holes known are only about as big as the orbits of the outer planets.