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Published bySuharto Sumadi Modified over 6 years ago
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Clusters Clusters and Age Stars are born from molecular clouds
Usually many stars born, not just one A cluster is a group of stars that are together and were probably born at the same time Some stars leave the cluster later – probably our Sun Because they were all born at the same time, they will be the same age By comparing the H-R diagram of a cluster to theoretical models, we can deduce the approximate age The turn off point
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Types of Clusters There are two types of clusters
Open clusters are loosely bound together Up to a thousand stars Generally younger stars In the disk of galaxies (more on this later) Globular clusters are more tightly bound A few thousand to one million stars Generally older stars Not confined to disks of galaxies (more on this later)
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Open Clusters NGC 290 M35 NGC 2158 Pleiades M6 M36
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Globular Clusters M3 M80 M10 M2 M13
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Cluster Diagrams: A cluster diagram is a Hertzsprung Russell diagram showing all the stars in a cluster Recall: Stars are “born” as Main Sequence Stars Massive stars are the hot luminous ones The most massive stars die first Over time, the cluster diagram will change:
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Cluster Diagram: 1 Million years
At 1 million years old: Some stars aren’t even main sequence yet The brightest stars, though rare, dominate the light O and B stars Blueish tint to the cluster The Sun
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Cluster Diagram: 10 Million Years
At 10 million years old: Almost all stars are now main sequence Some of the heaviest are in their supergiant phases The transition determines the turnoff point Some of them have died Turnoff
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Cluster Diagram: 30 Million Years
At 30 million years old: More stars are supergiants Turnoff point has moved Mix of stars now White color to cluster Turnoff
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Cluster Diagram: 200 Million Years
At 200 million years old: Red giants, core helium- burning, and double shell-burning Turnoff point moved farther Yellow tint to cluster Turnoff
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Cluster Diagram: 2 Billion Years
At 2 billion years old: G, K, M stars dominate Yellow/orange tint to cluster Turnoff
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10 Billion Years At 10 billion years old: K, M stars dominate
Red tint to cluster Sun is about to turn off Turnoff
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The Turnoff Point Clusters move around on H-R diagram over time
The turnoff point tells us how old the cluster is The color of a cluster changes from blue (young) to red (old) over time The Sun is not in a cluster
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