Thaha, that is Galaxy, the earth's galaxy," Milky way".. The core of the galaxy supposedly is a black hole... U cant really see where the black hole is, as light can't escape out of it. An assumption is the dense part is gas surrounding a black hole which is illuminated because of the force that generated massive energy.. Izen, we may not be alone... If not in our planet, may somewhere like earth in some other galaxies.There are number of known/unknown galaxy like ours.. Who knows what are there in andromeda I , II and III..