Model of the MW galaxy?

it is believed that our galaxy is almost the age of the universe at 13.2 billions year old - however others suggest its is only about 8. No one is very sure but evidence suggests that by a couple billion years, the nearest galaxy Andromeda is on its way to merging with our galaxy creating one big galaxy with explosions to last for millions of years until it all settles. There is an estimation of 200 - 400 billion stars and 500million planets.and with a diameter of 1000 light years. Our galaxy is a spiralled shaped galaxy and is beleived that one of the oldest stars present in the galaxy is about 13bn years old. At the center of our galaxy, and predicted the majority of galaxies, lies a bright radio source called Sagittarius A* which is now confirmed to be a super-massive black hole. It certainly cannot be seen by the darkness of it individually, but is a very compact and bright area in Sagittarius A* as light is emitte dof the peaks of the event horizon of the black hole and its surrrounding bodies. it is detected by observing the wobbles and orbits of the stars and systems close to the black hole. hope this helps your undestanding :)