Observing the Galactic Suburbs

Our Milky Way galaxy is often described as a flat­tened disk of hun­dreds of bil­lions stars. That descrip­tion leaves out some of our galaxy’s most inter­est­ing parts. Hov­er­ing above and below the main disk are the sub­urbs of our galac­tic city — 150 or so glob­u­lar clus­ters of stars. Along with some stray stars and occa­sional gas mol­e­cules, glob­u­lar clus­ters are the main con­stituents of what is more prop­erly called the “galac­tic halo.”