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Spiral galaxies are the star factories of the universe. A spiral galaxy’s arms are lanes where dust and gas pile up.
Raw dust and gas go into one side of a spiral arm, and newborn stars come out the other. The last step in star birth is an open star cluster. That’s where a flock of young stars drift through space until they slowly spread apart like autumn leaves in the wind.
Two Types of Clusters
▲ Open Clusters
Young stars are found in open star clusters. The stars in any particular open star cluster were all formed at about the same time within the same cloud of dust and gas. Because of their youth, these stars burn hot and bright. The clusters they form are loose and uncrowded. One of the open star clusters that’s easiest to see is the Pleiades (above), or Seven Sisters. Seven stars can be seen with the naked eye, but telescopes reveal over 3,000 stars.
▲ Globular Clusters
Older stars generally make up what are known as globular clusters. Containing as many as 1 million stars, these clusters have enough gravity to hold themselves together over billions of years. Stars in globular clusters are packed together in the core of these clusters. Sometimes they even collide. The core of one of the nearest globular star clusters, NGC 6397 (above), resembles a treasure chest of glittering gems.
▲ Star Power
This stellar jewel box is one of the most massive young open star clusters in the Milky Way. It is found within the giant nebula NGC 3603. The central open star cluster contains thousands of stars more massive than our Sun. These stars likely were born only 1 or 2 million years ago in one burst of star formation.
▲ Cluster Generations
The star cluster NGC 346 contains more than 2,500 newborn stars. It is in the center of one of the largest star-forming regions in the small neighboring galaxy the Small Magellanic Cloud.
◀ A Firecracker Cluster
The star cluster Hodge 301 lives inside the Tarantula Nebula in our galactic neighbor, the Large Magellanic Cloud. Many of the stars in Hodge 301 are so old that they have exploded. They are blasting material into the surrounding region at speeds of almost 200 miles per second! The high-speed matter is plowing into the surrounding nebula. The impact shocks and compresses the gas into long strands.
