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Star Clusters

A Sample of Stellar Life Cycle

Open Cluster Formation

In Figure 06-07a, different stages of a star's life cycle appear in this Hubble Space Telescope picture of the environs of galactic emission nebula NGC3603. For the beginning, eye-catching "pillars" of glowing hydrogen at the right signal newborn stars emerging from their dense, gaseous, nurseries. Less noticeable, dark clouds or "Bok globules" at the top right corner are likely part of a still earlier stage, prior to their collapse to form stars. At picture center lies a cluster of bright hot blue stars whose strong winds and ultraviolet radiation have cleared away nearby material. Massive and young, they will soon exhaust their nuclear fuel. Nearing the end of its life, the bright supergiant star Sher 25 is seen above and left of the cluster, surrounded by a glowing ring and flanked by ejected blobs of gas. The ring structure is reminiscent of Supernova 1987a and Sher 25 itself may be only a few thousand years from its own devastating finale. The two teardrop-shaped objects below the cluster toward the bottom of the picture are similar to suspected protoplanetary disks encompassing stars in the Orion Nebula as shown in Figure 07-01.

Figure 06-07a NGC 3603, Stellar Life Cycle

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