A white dwarf, also called a degenerate dwarf, is a stellar remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to that of the Sun, while its volume is comparable to that of Earth.

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O-type stars are very hot and extremely luminous. These are the rarest of all main-sequence stars. About 1 in 3,000,000 (0.00003%) of the main-sequence stars in the solar neighborhood are O-type stars.

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B-type stars are very luminous and blue. As O- and B-type stars are so energetic, they only live for a relatively short time. About 1 in 800 (0.125%) of the main-sequence stars in the solar neighborhood are B-type main-sequence objects.

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A-type stars are among the more common naked eye stars, and are white or bluish-white. About 1 in 160 (0.625%) of the main-sequence stars in the solar neighborhood are A-type stars.

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An F-type main-sequence star (F V) is a main-sequence, hydrogen-fusing star of spectral type F and luminosity class V. About 1 in 33 (3.03%) of the main-sequence stars in the solar neighborhood are F-type stars.

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