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Helix Nebula

A Dictionary of Astronomy | 1997 | 502 words | Copyright

Helix Nebula A planetary nebula in Aquarius, also known as NGC 7293 or sometimes the Sunflower Nebula. It is the nearest planetary nebula, 700 l.y. away, and the largest in apparent size, nearly ¼° across; the true diameter is about 3 l.y. It is ionized by a very hot 13th-magnitude central white dwarf of spectral type DA and temperature 120 000 K. The nebula's name comes from the fact that on early photographs it appeared somewhat helical in shape, like two overlapping loops of a spiral.

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