black holes collision-Abell 400 galaxy-gravitational waves

Stunning image indeed! Thanks for pointing out the article, Jeannot.

The black holes in the image that Mike posted are still about 28,000 light years apart. I followed the link mentioned in the article regarding the pair of black holes that are only 3000 light years apart (in the galaxy NGC 6240) to see if there was any imagery, and sure enough: :)

(Click the pic to go to the article “Black holes are double trouble for galaxy� from 20 Nov '02)

Imprassive, but I wash the modia were mere pricese weth there luggage:

'amounts of power' would be probably what they meant. Time rate of change of energy ......

Cheers, Mike.

The output is Lumens. For the analogy, I don't see it yet, so I'm not sure if it is good or bad.

Mike Hewson- Look at the source, even if it is wrong in a technical sense, it is appropiate for the audience. Power by and large to that audience is what comes from that socket on the wall, energy is everything else. I'll withold any social commentary about this, and just say it probably was the best choice of words.

I know what you mean. :-)
My worry was if it's combined with 'more than all the stars in the universe combined', then you've created a paradox. So now there's the hidden question/assumption as to whether a black hole is defined to be a star or not.... sigh.

Chipper, power is defined as the first time derivative of energy. You can apply this anywhere that energy changes. Since total energy is conserved, you're rating the 'conversion speed' between different forms. I think the idea originally goes back to steam engines and 19th century thermodynamics - you burn a pile of wood quicker and the train goes down the track faster, but you run out of wood earlier. A re-entering piece of space junk will spend it's kinetic and gravitational potential energy say by disassembling itself, heating the atmosphere and radiating light for you to appreciate it by, and no doubt sound waves to be heard if you're close enough. The time rate of this is power. Your internal chemistry, as we speak, can be rated accordingly - 'metabolic rate' - in this case handballing energy to different molecular configurations and random thermal motion ( to name a few ). Go for a jog and up goes your power, have a nap and down it goes.....
If two black holes collide they, relatively briefly, spray vast amounts of energy away, and almost exclusively in non-electromagnetic modes actually. After ringdown they're comparatively off the radar....
Cheers, Mike.

(edit) Power is not purely used to describe conversion processes alone. Transport of energy say. Define a surface in space, see energy moving across that surface in some mode ( say gravity waves ), then you have power per unit of area etc....

It will 'outshine' but not electromagnetically. If we were all born with gravity wave detectors, and that was a major mode of our sensations then it would be very 'bright' for us! So the author's comparison was ( rate of emission of ) gravitational radiation of the merger of two black holes vs. ( rate of emission of ) electromagnetic radiation of the rest of creation.
I know ........ I'm a pedant..... :-(
Cheers, Mike.

PS. Wouldn't it be cool to slip on a pair of gravity detector goggles - like night vision ones! Most of the Earth and solar system would be transparent and very dark and dull!