Cygnus X-1. That was the first place that Astronomers believed they had discovered a black hole. It has since gone from that to the knowledge that black holes are the core around which galaxies form. Not only that but they are the source of highly energetic Cosmic Ray’s. It is believed that Cosmic Ray’s are the spark that starts out lightening. Amazing to think that every time you hear thunder it began with a black hole millions of light years away.
Re: black hole millions of light years away
If Sagittarius A emits cosmic rays, they are “just” 25,000 light years away.