Want to take a guess at how many stars you’re looking at in this small patch of space? This bit of space, which is a part of the larger Omega Centauri globular cluster (the largest star cluster located in the Milky Way galaxy), contains over 100,000 stars. This is an astonishingly large number of stars lurking in an area that spans only 150 light-years across. It’s even more astonishing to learn that the 100,000 stars seen here are only a small fragment of the total number found in this dense cluster. It contains an estimated 10 million stars.
With the holiday season right around the corner, this festive cluster kind of sets the mood. Each of the various colors represent stars that are in different phases of stellar evolution. We have some that appear slightly orange or yellow, whilst others look blue or red. The contrast of coloring within the densely-packed stars is largely the result of numerous collisions and mergers. When these mergers occur, they can transform average sun-like stars into intensely hot and incredibly bright blue-white stars, called blue stragglers. Other times, neighboring stars siphon material from other stars located within the same general vicinity. (Not hard since each star is separated by less than 0.1 light-years) This results in the cannibal star becoming much brighter temporarily. There are also quite a few sun-like stars seen here, but red, by far, is the most prevalent color, indicating that this cluster is quite old, possibly around 12 billion years in age. In fact, it may be that this cluster was once the foundation of a dwarf galaxy – one that was disturbed long, long ago, by a gravitational interaction with a runaway galaxy—one that resulted in the Milky Way absorbing the stars in the cluster.
Overall, there are about 150 known globular clusters within the confines of the Milky Way galaxy. All of these clusters are thought to be among the oldest objects in the galaxy. Understanding their properties help astronomers pin down important information about the galaxy’s history, along with the age of the universe in general. This one in particular, Omega Centauri, is located about 15,000 light-years from Earth in the constellation known as Centaurus.
NASA has an awesome interactive tool that lets you explore the region. Check it out.