It depends on how you define it's edge. In a 10" ( 25 cm) telescope, a visual size is about 4 arc minutes in diameter. Many reference books list a size as large as 7.2 x 6.8 arc minutes. At a distance of 11 megaparsecs, 1 arc minute corresponds to about 3,200 parsecs or 10,300 light years. A diameter of 7 arc minutes then corresponds to 73,000 light years.
Copyright 1997 Dr. Sten Odenwald
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