🚀 go-pugleaf

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  >Certainly there is no way that a quasar can vary in brightness by a large 
  >amount on a time shorter than the light travel time across the source of the
  >energy. 
  >
  >Peter (theories to go) Allan

I've heard this argument a lot, but I wonder about it.  If the relativistic
beaming models are correct for "superluminous" quasar separations, then one
consequence is an effective "time squeeze" for the variability of the
ejected material.  As ejecta travel toward the observer at a substantial
fraction of lightspeed, any instrinsic variability on a modest timescale will
appear "foreshortened" in time to the observer, by the amount the separations
appear to exceed the speed of light.  

(No, I am *not* picking on you, Peter ... it only *looks* that way ...)

-- 
                                 Ed Nather
                                 {allegra,ihnp4}!{ut-sally,noao}!utastro!nather
                                 Astronomy Dept., U. of Texas, Austin