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A star whose spectrum shows the presence of the unstable element technetium. The longest-lived isotope of technetium has a half-life of 2.1 × 109 years, which is short in relation to the typical lifetimes of stars. (The age of the Sun, for example is 5 × 109 years.) The implication is that the technetium is being created within the star itself and subsequently brought to the surface; it could not have been in the material from which the star formed. Technetium has been detected only in a small group of carbon stars.
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