How does an atomic spectrum differ from that produced from the sun?

Question

What happens when electrons in atoms are heated or energized by electricity?
When do atoms release energy?
In what form is that energy released from the atom? Is that form always visible?

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Answer 1

An atom releases energy when an electron moves to an orbital of lower energy. The energy is released in the form of a photos with an amount of energy equal to that lost by the electron. The energy of the photon affects its wavelength, which affects its color (if it is in the visible spectrum). Since those wavelengths (called spectral lines) are specific to the different elements, emission spectra of stars can tell scientists what elements are present in the stars.