I've never seen that image of our galaxy's central region, it's fascinating! Is "Sgr A" the black hole, Sagittarius A*? If yes, why would it be bright? I thought it's inactive.
Sgr A is the black hole Sagittarius A* as far as I know. The black hole itself isn't bright. As far as I understand, the swirling gas around it (outside the event horizon) is what's sending out all the light.
By inactive I meant that it's not swallowing anything currently, but I guess if it has attracted a gas cloud this is simply not true. Must be quite a sight. Imagine there's a civilization on one of the central stars (if that's even possible considering the bursts of radiation they must get there) - I wonder what the night sky would look like.
The activity level (in terms of how much material is falling into it) is fairly low, such that it doesn't qualify as being an "active galactic nucleus". However, a gas cloud (called "G2") will be passing close enough to the supermassive black hole that it will be tidally disrupted and part of the cloud will fall into the black hole. This will give us a chance to see enhanced accretion, though still not of the level for it to be considered "active".
