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The Epic Interactive Encyclopedia 1998
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Epic Interactive Encyclopedia, The - 1998 Edition (1998)(Epic Marketing).iso
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Planetary_nebula
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INFOTEXT
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1992-09-02
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A shell of gas thrown off by a star at the
end of its life. Planetary nebulae have
nothing to do with planets. They were named
by William Herschel, who thought their
rounded shape resembled the disc of a planet.
After a star such as the Sun has expanded to
become a red giant, its outer layers are
ejected into space to form a planetary
nebula, leaving the core as a white dwarf at
the centre.