The galaxy in which we live, usually referred to simply as the Galaxy, or the Milky Way, which is actually only the portion visible to the naked eye, is a giant spiral assemblage of several billion stars; including our Sun. its true shape, size, and nature were not discovered by astronomers until the 20th century. It is now known to be an immense disk shaped object, far larger than most of the galaxies is its immediate neighborhood. Its visible disk has a diameter of approximately 100,000 light years and a height above its principle plane of about 1,000 light years, although some kinds of objects, such as globular Cluster, extend much farther above the galaxies plane.
The total mass of the galaxies can be measured by studying the motions of individual stars and clouds of hydrogen gas in deferent parts of the galaxies and by applying Celestial Mechanics to calculate a total mass that will account for the observed motions. The mass can be determined from the motions of the Galaxy’s small satellite galaxies, especially the nearby dwarf elliptical galaxies and globular cluster. Computational by both methods agree that the Galaxy’s mass is possibly 1,000 to 2,000 billion times the mass of the Sun. As the Sun’s mass is about average for a star in the galaxy, the total number of stars must also be of this order. Most of these stars are invisible from the Earth, however, because of the solar system lies in the dense of the Galaxy, where interstellar dust obscured all but its nearer parts.
After human have improve their space technology to see the amazing of this galaxy, we still can't have an exact explanation about the real condition about our space.