| 31. | The older open clusters tend to contain more yellow stars.
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| 32. | They may be former members of a dissolved open cluster.
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| 33. | Under exceptional conditions, open clusters can remain intact for up to 100 million years.
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| 34. | It is a member of the Collinder 121 open cluster.
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| 35. | IC 410, a faint nebula, is accompanied by the bright open cluster NGC 1893.
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| 36. | Open clusters are also easily detected in many of the galaxies of the Local Group.
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| 37. | In the foreground is the open cluster NGC 6530.
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| 38. | Open clusters are often classified according to a scheme developed by Robert Trumpler in 1930.
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| 39. | The closest open clusters can have their distance measured directly by one of two methods.
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| 40. | R136 itself is just the central condensation of the much larger NGC 2070 open cluster.
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