One of my research teams has conducted a comprehensive census of star formation in our neighboring galaxies. The program, the Local Volume Legacy (LVL), has targeted a total of 258 galaxies for study. LVL captures all known galaxies in a sub-volume bounded by 3.5 Mpc (11 million light years), and a statistically complete sample of star-forming galaxies extending to 11 Mpc (36 million light years). The volume probed by our survey is schematically represented by the line diagram below, where the Milky Way galaxy is located at the center of the diagram. With LVL, we seek to gain deeper insight into how stars, gas and dust evolve and interact, by analyzing ultraviolet, H-alpha, and infrared images.  

The data shown have been taken by the Spitzer Space Telescope. The color maps were created by combining 3.6 micron (blue), 8 micron (green) and 24 micron (red) imaging, which respectively represent the light from stars, polycyclic aromatic hydrocarbons, and dust grains that have been heated by newly born stars. The galaxies are randomly arranged but their relative sizes are as they appear on the sky.  


 

A grayscale version of the images, with labels giving the name of each galaxy, follows below. Virtually all of the galaxies pictured are classified as "spiral" and dwarf irregular" types. Such galaxies contain stellar nurseries where stars have been born from the gravitational collapse of gas. These nurseries give the galaxies much of their clumpy appearance. The galaxies have masses that range from about half a trillion times the mass of our sun (the spiral types, which are similar to our Milky Way), to ten million times the mass of the sun (the dwarf irregular types, which are similar to two galaxies visible from the Southern Hemisphere, the Small and Large Magellanic Clouds). The dwarfs look like smudges, which are almost entirely blue above, and are the most common type of galaxies in the universe.