What kind of objects make up most of the visible matter in a galaxy

 dust,gas,and stars make up most of the galaxy and for that, when a star dies out it explodes and all this stuff i've named is what happens. and blak holes start until a new star comes up and all that dust and gas  makes up most of the galaxy.  i don't know the rest .i'm sorry

compass can be used day and night, cloudy or sunny

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me