Wouldn’t it be, you know, a big black spot?
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Black holes tend to be a giant dark spot – surrounded by a gas cloud that is heated to billions of degrees by friction and compression as it falls into the hole. They have a disk like Saturn except that disk glows brighter than the rest of the galaxy combined.
Edit: in the case of the Milky Way the brightness is just star density, our black holes aren’t compressing quite enough matter to do super flashy stuff. Also, black holes are not that big. The one in the center on the Milky Way, Sagittarius A*, is smaller than Mercury’s orbit. IIRC there are several stars orbiting it that are larger than that (but far from being heavier of course).
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There’s a lot of stars near the center of the galaxy. Compared to the size of the galaxy the supermassive black hole is actually quite small.
Here’s a video [of stars orbiting the black hole at the center of the milky way](https://youtu.be/ChJU3pWRcrA). We can see them all fine because even though the black hole is massive, it’s still tiny compared to the distances of even its closest stars.
So the center of the milky way is bright because there is a dense cluster of stars there and the black hole is far too small to block their light.
It is supermassive but compared to the galaxy still not very large. Its diameter (event horizon) is only about 1/5 of the distance of mercury to the sun. Compared to the whole galaxy this is abysmally small. The Milky Way is 500 billion times larger than the supermassive black hole at its center.
It’s not just the black hole but what’s around it (the accretion disk). The hole itself is black, but consider spacetime. When we see a solar eclipse, we have seen stars that are geometrically behind the sun, but light from them travels in a straight line around the sun such that we can see them.
Now that effect would be massively intensified with an object as massive as a black hole to the point where we should see every star warping around it, and possibly even our own reflection lightyears in the past. From any angle, we should see millions of stars, making it a super bright object.
because the bright spot at the center of the galaxy is roughly across in any direction made of a bunch of orbiting stars. And the blackhole is only 14 million miles across.
Galaxies are HUGE
Two reasons:
the first is that black holes swallow light, so light accumulates at the event horizon
The second is that time is distorted near the event horizon, so the time to reach and cross the event horizon appear infinite to us.
So what you’re really seeing is all the accumulated light of stars, planets, civilizations as they wait their turn to be snuffed out of existence at the end of eternity.
So a black hole can’t be seen visually. That’s why they’re black holes! The light can’t escape, the photons can’t hit your eyes so we can’t see it.
Supermassive in this context doesn’t mean large, it means literally it has a _lot_ of mass all compressed into one thing – a black hole. It’s gravity is so strong that the entire galaxy is orbiting around it.
So the brightness is from the stars that are orbiting the black hole.
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