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Sodium (Na) is the element with atomic number 11, symbol Na. It has one stable isotope (mass number 23). Sodium nuclei originate from carbon burning in large stars. Sodium spectral lines are seen in the Sun, e.g., Fraunhofer D lines, two prominent yellow lines, and I presume at least some other stars show detectable sodium. A layer of Earth's atmosphere has a fair amount of neutral sodium (the sodium layer), and laser guide stars, which are used for adaptive optics in astronomical telescope observation, are often formed by a resulting glow of that sodium at a spot where a laser is pointed.