Quote:
Originally Posted by astroron
IC 2497 at only 700 Million light years away, Seems to me to be a little bit close to have a Quasar turn off only a million years ago 
This could encourage Arp devotees who say that Quasars are always not Billions of light years away 
It should be a very interesting discussion 
Cheers |
Not really....the simple, prosaic and most likely explanation is that
quasar like activity occurred in the nucleus of this galaxy just recently and only lasted for a limited period of time. The fact that it appears it turned off only about 70,000-200,000 years ago is just our good fortune to be observing it at the right time. The light still had to take 700 million years to get here, so what we're seeing (like a lot of astronomy) is nothing more than an illusion. It never shut off 200,000 years ago in our own perception of time, but over 700 million years ago in reality. The Voorwerp is nowhere near, now, where we see it as it is in the piccies. It might not even exist anymore for all we know.
A quasar, or quasar like activity, can switch itself on or off at anytime in a galaxy during its lifetime. All the quasar needs is an infall of material into the nucleus of the galaxy in which it resides to trigger it off. That could happen at any time, for a great many reasons. The only reasons why quasars and such were more prevalent in the past than now and shut off at similar times is because the galaxies in the earlier times had more material in their nuclei as dust, gas etc...especially during their formative years. More material meant more activity as the central holes gathered the materials to generate the quasars. But that activity will only last as long as the supply of material continues. In many ways, the central BH's are their own worst enemies because the high energy radiation given off in the quasar activity eventually drives the activity to a halt, by expelling the last of the material that's gathered in the near vicinity of the BH. That, and the fact that the hole can only suck in what it can during the life of the activity...which to generate a quasar only needs to be on the order of 1 solar mass/year. It can be more, though, but it's not like what most people would think (hundreds or thousands of solar masses in days, weeks or months).
There's no need for Arp's ideas to even be considered...not that they really hold any water, anyway.