Halloween Post – Quasar Ghosts

 

I’ve been saving this one for a few months, specifically for my Halloween post! This was such an interesting story, it was hard for me to pass it up before.  There are ghosts in these distant galaxies!

NASA, ESA, Galaxy Zoo Team and W. Keel (University of Alabama, USA)

Look at the images above, and see the ghostly green figures.  They are ionized Oxygen, helium, nitrogen, sulphur, and neon that has absorbed high energy radiation and slowly re-emitted it over thousands of years.  The photoionized gas clouds in the images are tens of thousands of light years outside their host galaxies, so where did this high energy radiation come from?

The answer, is quasars.  A quasar is a galaxy with a supermassive black hole at its centre that is rapidly swallowing up material, heating surrounding gas to millions of degrees, and producing radiation so powerful it often dwarfs the energy output of its entire host galaxy.  The interesting this about the above galaxies is that they aren’t quasars! So where did the energy come from?

The galaxies above may not be quasars right now, but if their supermassive black holes were swallowing up material tens of thousands of years ago, they could have released the kind of energy needed to ionize the distant gas! This is what is happening! The energy output of these quasars subsided tens of thousands of years ago, but the energy from them was still radiating outwards and ionizing the surrounding gases.  The gases slowly re-emit the energy over thousands of years, long after the quasar has died out.

Ghosts are real, but only with the strange time-delay of the vast distances in the universe.  Happy Halloween!

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