Spiral Galaxy M81
Elliptical Galaxy M87
Galaxies come in two different types: Spirals and Ellipticals. When most people think of a galaxy, they think of the classic spiral galaxy with a twisted arm shape (like M81 pictured above). These bright spiral arms contain most of the stars in the galaxies, which is why they are so bright. The number of spiral arms, how compact they are, and the direction they face varies between galaxies. Most spiral galaxies have a central black hole where all the spiral arms meet. Elliptical galaxies (like M87 pictured above) don't really look like a galaxy at all. They are essentially a huge collection of stars, often in an oval shape, and look like a bright fuzzy cloud, or out of focus star. These galaxies have little structure, other than the density of stars increases towards the center, where a black hole often lives. The next ADYK will discuss Edwin Hubble's galaxy classification scheme, a way of categorizing these types of galaxies based on there shape and structure.
