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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. 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 given 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 easiest open clusters 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. These clusters contain as many as 1 million stars. They have enough gravity to hold themselves together over billions of years. Stars in globular clusters are packed together in the core of the clusters. Sometimes they even collide. The core of one of the nearest globular star clusters, NGC 6397 (above), looks like a treasure chest of gems.
▲ Star Power
This stellar jewel box is one of the most massive young open star clusters in the Milky Way. It is inside the giant nebula NGC 3603. The central open star cluster has thousands of stars more massive than the Sun. These stars likely were born in one burst of star formation. That probably happened only 1 or 2 million years ago.
▲ 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 areas of the Small Magellanic Cloud. That’s a small galaxy near the Milky Way.
◀ A Firecracker Cluster
The star cluster Hodge 301 is inside the Tarantula Nebula. This nebula is located in our galactic neighbor, the Large Magellanic Cloud. Many of the stars in Hodge 301 are so old they have exploded. They are blasting material into the area around them at speeds of almost 200 miles per second! The high-speed matter is plowing into the nebula. The impact shocks and squashes the gas into long strands.
