... Credit: W. Keel and R. White ( U. Alabama ), NASA Explanation: This striking pair of galaxies is far, far away ... about 350 million light-years from Earth . ... The background elliptical and foreground spiral galaxy are representative of two of the three major classes of galaxies which inhabit our Universe . Within the disks of spiral galaxies , like our own Milky Way , gas, dust, and young blue star clusters trace out grand spiral "arms". ... Publications with keywords: Elliptical Galaxy . ...