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The nebula was the first nebula discovered to contain "cometary knots" and is believed to have on the order of 20,000 such knots.<ref name=nasa>[https://apod.nasa.gov/apod/ap080413.html Curious Cometary Knots in the Helix Nebula ] from apod.nasa.gov</ref> These knots comprise of a bright globules of material with tails that extend radially out from the nebula (point away from the nebula). These knots, which have masses similar to that of [[Earth]] but have radii several times the distance between [[Pluto]] and the [[Sun]] (some 100 [[Astronomical unit|AU]]), have been observed in other planetary nebulae such as the [[Ring nebula]], the [[Dumbbell nebula]] and the [[Eskimo nebula]].<ref name=nasa/> It has been suggested they are formed by a strong stellar wind produced by the nebula's central star.<ref name=nasa/>

The nebula was the first nebula discovered to contain "cometary knots" and is believed to have on the order of 20,000 such knots.<ref name=nasa>[https://apod.nasa.gov/apod/ap080413.html Curious Cometary Knots in the Helix Nebula ] from apod.nasa.gov</ref> These knots comprise of a bright globules of material with tails that extend radially out from the nebula (point away from the nebula). These knots, which have masses similar to that of [[Earth]] but have radii several times the distance between [[Pluto]] and the [[Sun]] (some 100 [[Astronomical unit|AU]]), have been observed in other planetary nebulae such as the [[Ring nebula]], the [[Dumbbell nebula]] and the [[Eskimo nebula]].<ref name=nasa/> It has been suggested they are formed by a strong stellar wind produced by the nebula's central star.<ref name=nasa/>

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==References==