Probably the brightest thing that pops up in your mind is the sun. but you see, brightness depends on distance and so the closer something is the brighter it is. The Sun might appear brighter than for instance Sirius just because it is closer, even though Sirius is 25 times brighter or a bulb could appear brighter than the sun if close enough.. So we shall consider their brightness at the same distance.
The sun is indeed very bright but it’s punny compared to the cosmos. It’s not even up there in the list of the brightest of stars. The Brightest star currently known is Godzilla which is 10.9 billion light years away from earth. Which is over 15 000 000 times brighter than the sun!
But wait, that’s not all. When these huge stars explode, they do so violently in a phenomenon called a supernova, ejecting terrifying flashes of radiation known as gamma ray bursts; the brightest electromagnetic event in the cosmos. But they only last for a few seconds to a few minutes at most.
Just how energetic are these bursts? Well they typically emit as much energy in a few seconds as the sun will do in its entire 10 billion years of life time. They are terrifying, if for instance WR104’s supernova (which scientists predict is very possible) strikes earth with this beam for about 10 seconds, it will lead to mass extinction and starvation. Mind you, this WR104 is 8000 light years away.. That’s very very very far.
Now here’s where it gets interesting.. If you want to look at something that lasts longer than a supernova and is incomprehensibly bright, you’ll have to look towards the darkest thing in the cosmos; Black holes!
But aren’t they those thingies that do not let even light escape? How can they be the source of brightness? Well these absurdities create intense amounts of energy in the process of eating stars and debris; which swirl, forming these discs around it before they pass the event horizon(the point at which even light cannot leave.. beyond it we don’t really know what happens). In these discs, matter is pulled around at unfathomable speeds and the resulting friction between this matter generates heat on a level that is difficult to comprehend. And like all hot things, this disc glows too. These are known as quasars. They shine thousands of times more brightly than entire galaxies containing billions of stars! Read that again. Isn’t it a bit too unreal?
For example TON618, a quasar 18.2billion light years away, is 140 trillion times brighter than the sun or over 3000 times brighter than the total amount of light produced by the milky way. The Milky Way is home to billions of stars, many of which are brighter than the sun!
If outflows of ionized matter are emitted from these towards an observer, they are even brighter. We call them blazars. And the blazar 3C454.3 clocked in the brightest entity ever observed with an absolute magnitude of -31.4. That’s 44 000 000 000 times brighter than the sun!!
Isn’t it amazing how the thing that consumes light is in essence the thing that produces what emits the most light?
Funnily, this is limited to our very minute observations (we can’t EVER even observe the whole universe since it is expanding at the speed of light) and we know nothing, Literally nothing about the universe so it is in fact an even crazier place out there and the actual brightest entity is probably wayyyyyy more absurd than this!
Interesting bit of information:
Most of the quasars are very far away, billions of light years often. Why? Because they don’t last forever. When we look at them, we are in essence looking at them as they were billions of years ago. They are a commodity of the early history of the universe, an era in which gigantic blackholes had not yet eaten all the stars around them and before they became too fat.
You see a black hole must consume 10 stars a year in order to remain a quasar host. Many consume much much more than that, thousands and thousands a year but that doesn’t mean that all of them host a quasar, you seee the more a black hole consumes, the wider is its event horizon and well when its big enough, it doesn’t shred apart stars but it just gollups them whole! Which means that they don’t make these discs.
So quasars are in essence a relic of the initial stages of the universe but they can occur even now.. scientists predict that the collision of our galaxy with the Andromeda galaxy will result in a quasar in our very own galactic backyard.