The Local Galaxies 1. Spiral galaxies have diameters ranging from 5000 to 50,000 parsecs, Irregular galaxies are from 1000 to 10,000 parsecs across, and Ellipticals range from 1 to 200,000 parsecs, so Ellipticals are the largest type of galaxy. Spirals and Irregulars have about the same luminosity range, but Ellipticals can be a bit fainter in appearance, in part due to their small amounts of gas and dust. Ellipticals are composed mostly of old stars.
Elliptical galaxies are the most common in the universe.
Galaxies and the Expanding Universe 6. The farther out we look into space, the farther back into the past we are seeing. A light-year is defined as the distance light travels in a year. Distant galaxies are billions of light-years away, so we are seeing the light from these galaxies from billions of years ago. Some of the most distant galaxies are over 10 billion light-years away, so the light that we receive from them comes from a time when our galaxy was just forming.