These days the nature of galaxies is largely beyond speculation, even although we continue to work at establishing accurate intergalactic distance measurements. Galaxies are huge agglomerations of stars, and vast quantities of dust and gas, all bound together by gravity. Our galaxy, the Milky Way, is variously estimated to contain 100 to 200 billion stars. As early as 1957, over one million galaxies had been counted on Harvard Observatory photographs. It's estimated that over a billion are within reach of the 200-inch Hale telescope on Mt. Palomar, and the Hubble Space Telescope promises to reveal many more.
Galaxies are very large, with typical diameters of tens to hundreds of thousands of light years.
Given these dimensions, it's interesting to contemplate one astronomer's observation that the universe is more densely populated with galaxies than a galaxy is with stars. They occur in a variety of shapes and sizes. Elliptical galaxies are disk-like or spheroidal assemblages of stars with little or no internal structure. The class is further divided into subgroups according to their apparent flatness, from E0, the roundest, to E7, the flattest. Spiral galaxies are those exhibiting an overall spiral structure.