Sentences with phrase «internal nuclear reactions»
Too large to be considered planets, but too small to spark the internal nuclear reactions necessary to become full - blown stars, brown dwarfs — aka «failed stars» — are of particular interest to astronomers because of what they can teach us about planetary and star formation.
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About half the heat produced by Earth is thought to come from internal nuclear reactions, the other half from heat left over from Earth's earliest days as a red - hot planet.