Globular clusters are the oldest visible objects in the Universe – each contains hundreds of thousands to occasionally over one million stars, all born at essentially the same time. They are densely packed into a spherical volume with a diameter over a thousand times smaller than the diameter of the Milky Way Galaxy. Globular clusters are thought to have formed soon after the Universe began nearly 13.8 billion years ago, at the same time as, or perhaps even before, the first galaxies formed.
Harbor Oldest Stars in the Universe
Some of the oldest stars in the universe are found in ancient globular clusters that orbit around the halo of our home galaxy. The Milky Way is circled by at least 150 globular clusters, each harboring hundreds of thousands, and sometimes millions of stars. Globular clusters formed very early in the vast halo surrounding the embryonic Milky Way before it flattened to form a spiral disk.